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Tektronix 5A21N User's Manual

1. SECTION 2 OPERATING INSTRUCTIONS Change information if any affecting this section will be found at the rear of this manual Introduction The 5A21N Differential Amplifier Plug In operates with a Tektronix 5100N series oscilloscope system An under standing of the 5A21N operation and capabilities is essen tial for obtaining best results This section of the manual gives a brief functional description of the front panel con trois and connectors a familiarization procedure and general operating information PLUG IN INSERTION AND REMOVAL The 5A21N is calibrated and ready for use as it is received It can be installed in any compartment of the 5100N series Power Supply Amplifier module but it is intended for primary use in vertical compartments the center and left compartments For X Y operation the 5A21N may also be installed in the horizontal right com partment refer to the Oscilloscope System instruction manual for information on X Y operation NOTE The Power Supply Amplifier module is designed so that in the absence of DISPLAY ON logic levels from the vertical plug ins it will display the output of the unit in the left compartment To install align the upper and lower rails of the 5A21N with the plug in compartment tracks and fully insert it the plug in panel must be flush with the oscilloscope panel To remove pull the release latch to disengage the 5A21N from the oscilloscope CONTROLS AND C
2. sion Accuracy Uncalibrated Var Range Frequency Response Bandwidth 8 Div 50 microvolts division to 5 voits division Within 2 0 5 milliampere division to 0 5 ampere divi 16 steps in a 1 2 5 sequence 10 steps in a 1 2 5 sequence Within 3 Step Attenuator Balance Adjustable for one division or less trace move ment as VOLTS DIV is rotated throughout its range At least 2 5 1 Reference DC Direct Coupled 1 MHz DC to at least 1 megahertz 10 kHz DC to 10 kilohertz Within 20 AC Capacitive Coupied 1 MHz 2 hertz or less to at least 1 megahertz 10 kHz 2 hertz or less to 10 kilohertz Gi Within 20 T1 Specification 5A21N Characteristic AMPERES Mode 1 MHz 10 kHz Step Response Displayed Aberrations Inputs Voltage Mode Resistance Capacitance Maximum Safe Input Voltages DC Direct Coupied 50 uV Div to 50 mV Div 100 mV Div to 5 V Div AC Capacitive Coupled 50 UV Div to 50 mV Div 100 mV Div to 5 V Div DC Rejection AC Capacitive Coupled Input Gate Current Current Mode TABLE 1 1 cont Performance Requirement 15 hertz or less to at least 1 megahertz 1 megohm within 0 1 47 picofarads 10 volts DC Peak AC 350 volts DC Peak AC 350 volts DC Coupling capacitor pre charged 10 volts peak AC 350 volts DC Peak AC At least 100 000 1 after 20 minute warmup 100 picoa
3. 2N4250 2N4250 284250 310 unless otherwise indicated lM OHM 0 25W 1M OHM 0 25W iK OHM 0 25W 10 OHM 0 25W 10 7K OHM 0 125W PREC 1 1 5K OHM 0 125W PREC 1 2K OHM 0 125W PREC 1 100 OHM 0 25W 5 20K OHM 0 25W 5 3 74K OHM 0 125W PREC 1 3 92K OHM 0 125W PREC 1 2K OHM 0 125W PREC 1 1 2K OHM IW 49 9 OHM 0 125W PREC 18 12 4 OBM 0 125W PREC 1 27 OHM 0 25W 5 990K OHM 0 25W PREC 0 1 iM OHM 0 25W PREC 0 1 10K OHM 0 125W PREC 0 25 200 OHM VAR 5 3 Electrical Parts List 5A21N Serial Model No Eff Dscont Tektronix Ckt No Part No RESISTORS CONT Rill 315 0153 06 R114 315 0242 00 R120 315 0201 00 R121 321 0261 00 25 322 0 078 0 R126 321 0126 00 R127 311 1116 00 R131 315 0270 00 R135 315 0331 00 R137 315 0362 00 R140 321 0816 03 R141 321 0816 03 R14 4 315 0153 00 R145 315 0153 00 R146 315 0682 00 R151 321 0222 00 R152 321 021600 R153 321 0231 0090 R155 321 0197 00 R158 32i1 0233 00 R159 311 1120 9090 R162 315 0153 0909 R167 321 0272 00 R168 321 0182 00 R168 321 0181 00 R169 311 1121 00 R170 315 0912 00 R171 315 0513 00 R174 316 0102 00 Ri75 321 0184 00 R178 315 0103 00 R181 316 0154 00 R182 316 0105 00 R184 315 0103 00 R185 316 0124 00 R187 316 0105 00 R200 315 0270 00 R203 322 0624 07 R206 322 0481 07 R208 321 0289 03 R211 321 0261 00 R220 315 0201 00 R227 311 0622 00 R240 321 0933 03 R241 321 0932 03 R242 321 0931 03 R243 321 0660 03 R244 321 0930 03 R245 321
4. 2 7 3 1 3 1 3 1 3 1 3 2 3 2 3 2 3 3 3 3 3 4 3 4 3 4 4 1 4 1 4 1 4 2 4 3 4 7 Fig 1 1 5A21N Differential Amplifier 5A21N 5A21N SECTION 1 5A21N SPECIFICATION Change information if any affecting this section will be found at the rear of this manual introduction The 5A21N Differential Amplifier is a high gain differ ential amplifier plug in unit for use with Tektronix 5100 series oscilloscopes and permits the measurement of current signals as well as voltage signals The unit features high sensitivity with direct coupled inputs 50 UV DIV or 0 5 mA DIV and has a high common mode rejection ratio An illuminated knob skirt provides deflection factor read out The unit has a bandwidth capability of DC to one megahertz and a front panel pushbutton switch allows reduction of the upper bandwidth limit thus increasing the signal to noise ratio for low frequency applications This instrument will meet the performance requirements listed in Table 1 1 following complete calibration as given in Section 4 The following electrical characteristics apply over an ambient temperature range of 0 C to 50 C in this manual the word Volts Div or division refers to major graticule division TABLE 1 1 ELECTRICAL CHARACTERISTICS Characteristic Performance Requirement Supplemental Information Deflection Factor VOLTS DIV Calibrated Range Accuracy AMPERES DIV Calibrated Range
5. 312 INCH WASHER LOCK INTERNAL 0 261 ID X 0 40 OD PLATE MOUNTING WASHER FLAT 0 35 ID X 0 37 INCH OD wn mm w w SWITCH PUSH 10 KHZ BANDWIDTH LIMIT ATTACHING PARTS SPACER SWITCH AREE EE SWITCH PUSH INPUT COU ING MODE ATTACHING PARTS SPACER SWITCH ee eee CLIP FUSE CONTACT ELECTRIAL ACTUATOR ASSEMBLY VOLTS DIV OR AMPERES DIV e DRUM BEARING REAR NUT HEX 4 40 X 0 188 INCH BRACKET SUPPORT BEARING FRONT CONTACT ELECTRICAL GROUNDING REV JUL 1974 Mechanical Parts List 5A21N FIGURE 1 EXPLODED CONT Fig amp Index Tektronix Serial Model No No Part No Eff Dscont Qty 2 3 45 _ Name amp Description 1 63 354 0219 00 l RING RETAINER 64 214 1127 00 l ROLLER DETENT 65 214 1139 03 l SPRING PLAT RED 66 214 1139 02 Ll SPRING FLAT GREEN 67 200 0943 01 l COVER ATTACHING PARTS 68 211 0079 00 l SCREW 2 56 X 0 188 INCH PHS 69 210 0001 00 3 WASHER LOCK 0 092 ID X 0 175 INCH OD 70 210 0259 00 1 LUG SOLDER 2 71 220 0636 00 4 NUT HEX 2 56 X 0 188 INCH ATTACHING PARTS 72 211 0116 00 6 SCREW SEMS 4 40 X 0 312 INCH PHB 73 mm meen Ll RESISTOR VARIABLE ATTACHING PARTS 74 220 0495 00 l NUT HEX 0 375 32 X 0 438 INCH 75 407 0894 0900 1 BRACKET 76 210 0012 00 1 a WASHRE LOCK INTERNAL 0 375 ID X 0 50 OD 77 384 0242 00 1 ROD EXTENSION 7 281 INCHES ATTACHING PAR
6. Frequency CMRR 4 4 6 Check High Frequency CMRR 4 5 7 Check Amplifier Bandwidth 4 5 8 Check Input Gate Current 4 5 9 Check Amplifier Noise Level 4 6 10 Check Current Probe Amplifier j 4 6 Gain 11 Check Current Probe Amplifier 4 6 Frequency Response Preliminary Procedure for Performance Check NOTE The performance of this instrument can be checked at any temperature within the 0 C to 50 C range unless stated otherwise 1 Insert the 5A21N into the left plug in compartment of the 5103N Oscilloscope System mainframe Insert a 5B10N time base unit into the right compartment 2 Connect the oscilloscope to the power source for which it is wired and turn on the power 3 Set the controls as given under Preliminary Control Settings e 1 Check Variable Balance a Move the trace to the graticule center horizontal line with the POSITION control b Rotate the Variable Volts Div control counterclock wise c CHECK Trace should not shift more than one divi sion as the Variable control is rotated throughout its range d CALIBRATION If shift is excessive perform step 1 of the Adjustment procedure e Return the Variable control to the CAL detent posi tion 2 Check DC Balance a Turn the VOLTS DIV switch throughout its range b CHECK Trace should not shift more than one divi sion Adjust the front panel STEP ATTEN BAL control for minimum trace shift as the VOLTS DIV switch is rotated throughout
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8. and passed through emitter foliower Q288 where it is made available to an associated time base unit via output terminal A4 The triggering signal is of the same polarity as that applied to the gate of Q120A and has an amplitude of about 0 25 volt per displayed division 3 4 Vertical Switching and Readout The VOLTS DIV switch 240 is made up of a series of cam lobes which engage and disengage various contacts at different positions of the switch Cams 1 through 4 control switching of the input attenuators and cams 5 through 13 control switching of the gain setting resistor R240 R249 in the preamplifier stage Those contacts that are engaged at any given position of the switch are shown by black dots on the switch logic diagram Either of two lamp bulbs located behind the knob skirt of the VOLTS DIV switch illuminates the selected deflec tion factor to provide a direct readout Normally DS182 which is physically located behind the upper left portion of the knob skirt is lit Connection of a readout coded 10X probe to either the or input automatically changes the readout by a factor of 10 ie extinguishes DS182 and illuminates DS187 to reflect the correction of probe atten uation eliminating possible error by the operator of the instrument J1 and J11 the and input connectors have probe rings allowing the 10X probe to apply a ground connection to the base of 0182 0182 turns off allowing 0187 to turn on swit
9. increase the parallel capacitance to 100 pF or more In many cases the effects of these resistive and capacitive loads may be too great and it may be desirable to minimize them through the use of an attenuator probe Attenuator probes not only decrease the resistive capaci tive loading of a signal source but also extend the measure ment range of the 5A21N to include substantially higher voltages Passive attenuator probes having attenuation factors of 10X 100X and 1000X as well as other special purpose types are available through your Tektronix Field Engineer or Field Office Some measurement situations require a high resistance input to the BA21N with very little source loading or signal attenuation in such situations a passive attenuator probe cannot be used However this problem may be solved by using a FET Probe or the high impedance input provision of the 5A21N High Impedance Input In the 50 mV through 50 UV positions of the VOLTS DIV switch where the input attenuator is not used the internal gate return resistors alone establish the 1 megohm input resistance The removal of the strap from the circuit board disconnects these resistors from ground and permits the input FET gates to float providing a very high input impedance see Fig 4 1 in the Calibration section for loca tion of the strap The signal source must then provide a DC path for the FET gate current The input signal must be kept to relatively low ampl
10. input Circuit Description 5A21N Assuming that a signal is applied to the input the applied signal is passed directly to the attenuators when both buttons are out When the AC button is pressed C4 is placed in the circuit to couple signals of about two hertz 3 dB point higher to the attenuator This capacitor blocks any DC component of the signal When the GND button is pressed a ground reference is provided to the input of the amplifier without the need to remove the applied signal from the input connector NOTE When DC levels above 10 volts are to be blocked by AC coupling both the AC and GND buttons should be pressed n PRE CHG while input connections are made or broken or when voltage levels are changed This will allow the coupling capacitor to charge with out blowing the input fuses or overdriving the ampli fier Current Probe Amplifier The current probe amplifier made up of Q20 30 and their associated passive circuitry is an operational amplifier which compensates for the probe characteristics When the CURR PROBE ONLY button is pressed S1C disconnects the and voltage inputs and connects the current probe signal to the input attenuators Probe signal is applied from J21 to the base of O20A and at the same time it is applied via C37 to the positive side of the preamplifier input The compensated signal is developed at the collector of Q30 and applied via C36 to the negative side of the preamp
11. operational amplifiers connected in a differential configuration Fig 3 1 shows a simplified block diagram of the Preamp Differential Signal Current Gain setting input Resistor Signal selected by VOLTS DIV switch Fig 3 1 input Preamp detailed block diagram showing signal current paths The operational amplifiers are composed of 01204 0129A and Q150A on one side and Q120B 0129B and 0150B on the other side Q120A and Q120B provide a voltage follower input to output transistors Q150A and Q150B Totai gain of the stage is determined by the resistance between the two sides of the amplifier and R153 and R253 the signal current path in Fig 3 1 Quiescently the two sides of the amplifier are balanced so that there is no current through R240 When a differ RE ential signal is applied to the gates of O120A and 01208 the signal current is developed through the parallel com bination of the gain setting resistor R240 R249 and R140 R 141 Conduction of Q150A and 01508 is changed by the amount of this current developing the output volt age across R 153 and R253 The output is a push pull signal opposite in polarity to the signal applied to the inputs The value of R240 R249 is selected by the VOLTS DIV switch 240 to determine the gain To minimize trace shift as different vertical deflection factors are selected the outputs at O150A and 01508 collectors are DC balanced at equal potentials s
12. remains un changed that is the common mode signal is rejected C221 CMRR 1 and C250 CMRR 2 are adjusted on high frequency common mode signals to normalize the effective capacitance of the active devices on one side of the amplifier to the other Isolation Stage The differential signal developed at the collectors of Q150A and Q150B is passed through emitter followers 0160 and Q260 to the output amplifier Q160 and Q260 Bl REV JULY 1974 3 3 Circuit Description 5A21N isolate the preamplifier from the loading of the output amplifier and trigger signal amplifier Output Amplifier The output amplifier consists of push pull amplifier Q163 Q263 With a signal applied potentiometer R268 Gain provides emitter degeneration the gain being deter mined by the total emitter resistance This allows the over all gain of the 5A21N to be adiusted to match the main frame requirements Also the Variable Volts Div control R169 allows gain to be adjustable over a 2 5 to 1 ratio 0170 and 0270 are positioning current drivers R179 POSITION provides an adjustable change in the con duction of the transistors which provide a current to either add to or subtract from the 0163 0263 currents to alter the quiescent vertical position of the display Trigger Signal Amplifier Differential amplifier 0280 0286 receives the triggering signal from the emitters of Q160 and Q260 in the isolation stage The triggering signal is amplified
13. temperature of 25 C 5 C for best overall accuracy 1 Remove the dust cover from the left side of the 5A21N and remove the cabinet panel from the left side of the 5103N Oscilloscope mainframe 2 Place the 5A21N on a plug in extender and insert the extender into the left plug in compartment of the 5103N Oscilloscope mainframe Insert a 5B10N time base unit into the right compartment Remove strap for R109 high impedance input Low Freq CMRR see Operating Instructions fnput Comp C13 C11 Ci a c C2 R227 input Comp DC Balance Fig 4 1 Location of internal controls in the 5A21N i Adjustment 5A21N 3 Connect the oscilloscope to the power source for which it is wired and turn on the power 4 Set the controls as given under Preliminary Control Settings 1 Adjust Variable Balance R 159 a Move the trace to the graticule center horizontal line with the POSITION control b Rotate the Variable Volts Div control counterclock wise c ADJUST R 159 Var Bal for minimum trace shift as the Variable Volts Div control is rotated throughout its range Re adjustment of the POSITION control may be necessary to return the trace to graticule center after the minimum shift has been attained d Return the Variable control to the CAL detent position 2 Adjust DC Balance R227 a With the STEP ATTEN BAL control centered turn the VOLTS DIV switch throughout its range b ADJUST 1f the trace goes of
14. 00 387 0794 00 210 0940 00 260 1208 00 361 0385 00 260 1210 00 361 0384 00 344 0154 00 131 0604 00 105 0239 00 105 0221 00 401 0056 00 220 0636 00 407 0653 00 401 0057 00 FIGURE 1 EXPLODED CONT Serial Model No EI rca SCONE B010100 B039999 B040000 131 1219 00 XB040000 2 1 1 1 1 1 2 1 BO BERR NOR Ri N RN Pi pap Ut pa der OY Fe F ta Lo Ps lt 12 d 4 B Name amp Description PUSH BUTTON GRAY CURR PROBE ONLY PUSH BUTTON GRAY AC PUSH BUTTON GRAY GND PUSH BUTTON GRAY ON DISPLAY SHAFT EXTENSION 6 581 INCHES LIGHT INDICATOR SHIELD LIGHT ATTACHING PARTS SCREW THREAD CUTTING 2 56 X 0 25 100 DEG CSK FHS mom Eo lt KNOB RED VARIABLE SETSCREW 5 40 X 0 125 INCH HSS KNOB CHARCOAL VOLTS DIV OR AMPERES DIV SETSCREW 5 40 X 0 125 INCH HSS PANEL FRONT SUBPANEL FRONT SHIELD ELECTRICAL FRAME SECTION TOP ATTACHING PARTS SCREW THREAD FORMING 6 X 0 375 100 DEG CSK FHS kosa a ae SHIELD SIDE FRAME SECTION BOTTOM ATTACHING PARTS SCREW THREAD FORMING 6 X 0 375 100 DEG CSK FHS CIRCUIT BOARD ASSEMBLY MAIN CIRCUIT BOARD ASSEMBLY MAIN CIRCUIT BOARD LINK TERMINAL CONNECTING SOCKET TRANSISTOR 6 PIN PIN TEST POINT SWITCH PUSH ON DISPLAY ATTACHING PARTS SPACER SWITCH lt E lt lt RESISTOR VARIABLE ATTACHING PARTS NUT HEX 0 25 32 X 0
15. 0347 00 0187 151 0347 00 0260 151 0341 00 0263 151 0219 00 0270 151 0341 00 0280 151 0219 00 0281 151 0341 00 Q286 151 0219 00 R4 316 0105 00 R14 316 0105 60 R21 316 0102 00 R22 316 0100 00 R23 321 0292 00 R24 321 0210 00 R24 321 0222 00 R25 315 0101 00 R27 315 0203 00 R32 321 0248 00 R32 32i1 0250 00 R33 321 0222 00 R35 304 0122 00 R36 321 0068 00 R37 32i1 0010 00 Ri00 315 0270 00 Ri03 322 0624 07 R106 322 0481 07 R108 321 0289 03 R109 311 0605 0090 Serial Model No Eff XBO40060 n04 0 BOLOLOO B040000 B010100 B040000 B010100 B040000 B010100 Dscont B039999 B039999 8039999 BO39999X REV JUL 1974 Electrical Parts List 5A21N Description 1 16A 3AG FAST BLO 1 16A 3AG FAST BLO 40U0H 40UH SUH WOUND ON A 200 OHM 0 25W 5 RESISTOR 5UH WOUND ON A 200 OHM 0 25W 5 RESISTOR SILICON NPN TEK SPEC DUAL SILICON PNP TO 18 REPLACEABLE BY 2N4250 SILICON PNP TO 5 2N5447 SILICON JFET TO 71 TEK SPEC SILICON PNP TO 76 TEK SPEC DUAL SILICON PNP TO 18 2N4122 SILICON NPN TO 98 2N5249 SILICON NPN TO 106 2N3565 SILICON NPN TO 78 TEK SPEC DUAL SILICON NPN TO 78 TEK SPEC DUAL SILICON NPN TO 106 2N3565 SILICON PNP TO 18 REPLACEABLE BY SILICON NPN TO 106 2N3565 SILICON NPN TO 92 2N5551 SILICON NPN TO 92 2N5551 SILICON NPN TO 106 2N3565 SILICON PNP TO 18 REPLACEABLE BY SILICON NPN TO 106 2N3565 SILICON PNP TO 18 REPLACEABLE BY SILICON NPN TO 106 2N3565 SILICON PNP TO 18 REPLACEABLE BY
16. 1 0081 00 1 8 13PF VAR AIR C2 281 0078 00 1 4 7 3PF VAR AIR C3 281 0081 00 1 8 13PF VAR AIR Cil 281 0081 00 1 8 13PF VAR AIR C12 281 0078 00 1 4 7 3PF VAR AIR 5 1 2 601 1681 Parts LISI SAZIN Serial Model No ER XB040000 B010100 B030000 B010100 B040000 B010100 B030000 Tektronix Ckt No Part No CAPACITORS CONT C13 281 0081 00 C22 290 0267 00 C25 283 0080 00 C27 281 0546 00 C32 290 0297 00 C33 281 0579 00 C36 290 0264 00 C37 290 0264 00 C38 283 0003 00 C101 281 0658 00 C104 281 0628 00 C104 281 0657 00 0008 283 0626 00 CELL 290 0267 000 C121 281 0604 00 C122 281 0604 00 C129 281 0709 00 C131 281 0504 00 C135 290 0267 00 C140 281 0534 00 C140 281 0504 00 C148 290 0297 00 C149 290 0297 00 C150 281 0618 00 C158 281 0504 00 C163 281 0540 00 C170 283 0000 00 C181 283 0002 00 C184 283 0002 00 C204 281 0628 00 C204 281 0657 00 C208 283 0626 00 C221 281 0114 00 C229 281 0709 00 C250 281 0077 00 C256 283 0003 00 C259 283 0041 00 C263 281 0540 00 C279 281 0586 00 C281 281 0534 00 C287 290 0134 00 SEMICONDUCTOR DEVICE DIODES CR111 152 0324 00 CR112 152 0324 00 CR113 152 0324 00 CR114 152 0324 00 CR163 152 0185 00 CR263 152 0185 00 VR111 152 0168 00 VR114 152 0168 00 VR148 152 0280 00 VR149 152 0279 00 5 2 Dscont B029999 B039999 B029999 Description 1 8 13PF VAR AIR lUF ELCTLT 35V 0 022UF CER 25V 80 20 330PF CER 500V 10 39UF ELCTLT 10V 10 21PF CER 500V 5 0 2
17. 1097 03 R246 321 0030 03 54 BOiG100 285039999 B040000 B010100 B039999X Description 15K OHM 0 25W 5 2 4K OHM 0 25W 5 200 OHM 0 25W 5 5 11K OHM 0 125W PREC 1 63 4 OHM 0 125W PREC 1 200 OHM 0 125W PREC 1 100 OHM VAR 27 OHM 0 25W 5 330 OHM 0 25W 5 3 6K OHM 0 25W 5 5K OHM 0 125W PREC 0 25 5K OHM 0 125W PREC 0 25 15K OHM 0 25W 5 15K OHM 0 25W 5 6 8K OHM 0 25W 5 2K OHM 0 125W PREC 1 1 74K OHM 0 125W PREC 1 2 49K OHM 0 125W PREC 1 L 1K OHM 0 125W PREC 1 2 61K OHM 0 125W PREC 1 100 OHM VAR 15K OHM 0 25W 5 6 65K OHM 0 125W PREC 1 768 OHM 0 125W PREC 1 750 OHM 0 125W PREC l1 2K OHM VAR 9 1K OHM 0 25W 5 51K OHM 0 25W 5 1K OHM 0 25W 806 OEM 0 125W PREC 13 10K OHM 0 25W 5 150K OHM 0 25W IM OHM 0 25W 10K OHM 0 25W 5 120K OHM 0 25W 1M OHM 0 25W 27 OHM 0 25W 5 990K OHM 0 25W PREC 0 1 1M OHM 0 25W PREC 0 1 10K OHM 0 125W PREC 0 258 5 11K OHM 0 125W PREC 1 200 OHM 0 25W 5 100 OHM VAR 6 66K OHM 0 125W PREC 0 258 2 5K OHM 0 125W PREC 0 25 1 11K OHM 0 125W PREC 0 25 417 OHM 0 125W PREC 0 25 204 OHM 0 125W PREC 0 25 101 OHM 0 125W PREC 0 25 20 OHM 0 125W PREC 0 25 REV JUL 1974 Tektronix Ckt No Part No RESISTORS CONT R249 321 0030 03 R251 321 0222 00 R253 321 0231 00 R255 321 0197 00 R256 321 0306 00 R257 321 0306 00 R258 321 0233 00 R262 315 0153 00 R267 321 0272 00 R268 311 1120 00 R274 316 0102 00 R275 321 0184 00 R27
18. 2UF ELCTLT 35V 10 0 22UF ELCTLT 35V 10 0 01UF CER 150V 80 20 6 2PF CER 500V 0 25PF l5PF CER 600V 5 amp 13PF CER 500V 2 1800PF MICA 500V 5 lUF ELCTLT 35V 2 2PF CER 500V 0 25PF 2 2PF CER 500V 0 25PF 7PF CER 500V 0 1PF lOPF CER 500V 102 lUF ELCTLT 35V 3 3PF CER 500V 0 25PF 10PF CER 500V 10 39UF ELCTLT 10V 108 3QUF ELCTLT 10V 10 amp 7PF CER 200V 0 5PF lOPF CER 500V 10 5 127 0237 8 0 001UF CER 500V 0 01UF CER 500V 0 01UF CER 500V 15PF CER 600V 5 13PF CER 500V 2 1800PF MICA 500V 5 1 3 5 4PF VAR AIR 7PF CER 500V 0 1PF 1 3 5 4PF VAR AIR 0 01UF CER 150V 0 0033UF CER 500V 5 51PF CER 500V 5 25PF CER 500V 5 3 3PF CER 500V 0 25PF 22UF ELCTLT 15V SILICON TER SPEC SILICON TEK SPEC SILICON TEK SPEC SILICON TEK SPEC SILICON REPLACEABLE BY 1N4152 SILICON REPLACEABLE BY 1N4152 ZENER 1N963A 400MW 12V 5 ZENER 1N963A 400MW 12V 5 amp ZENER 1N753A 400MW 6 2V 5 ZENER 1N751A 400MW 5 1V 5 REV JUL 1974 RESISTORS resistors are fixed composition Tektronix Ckt No Part No FUSES F20 15 0024 00 F206 159 0024 00 INDUCTORS Li74 108 0200 00 L274 108 0200 00 LR100 108 0565 00 LR206 108 0565 00 TRANSISTORS 020A B 151 0308 00 030 151 0219 00 030 151 0164 00 Q120A B 151 1049 00 Q129A B 151 0261 9090 0130 151 0220 00 Q140 151 0273 00 Q146 151 9341 9090 Q150A B 151 0232 00 Q158A B 151 0232 00 Q160 151 0341 00 0163 151 0219 00 Q170 151 0341 06 0182 151
19. 40 X 0 188 INCH HSS 213 0178 00 B040000 SETSCREW 4 40 X 0 125 INCH HSS 354 0251 00 2 RING 376 0049 00 1 COUPLING 14 366 1286 00 8010100 B039999 1 KNOB LATCH 366 1286 03 B040000 1 KNOB LATCH 214 1840 00 XB040000 1 PIN KNOB SECURING 15 214 1513 00 2010100 58039999 i LATCH PLUG IN 214 1513 01 B040000 i LATCH PLUG IN ATTACHING PARTS 16 213 0254 00 1 SCREW THREAD CUTTING 2 56 X 0 25 100 DEG CSK FHS GE 17 366 1257 15 i KNOB GRAY 10 KHZ BANDWIDTH LIMIT 18 384 1058 00 i SHAFT EXTENSION 7 781 INCHES LONG 19 366 1292 00 2 PUSH BUTTON GRAY 20 426 0681 00 7 FRAME PUSH BUTTON 21 366 1257 11 i PUSH BUTTON GRAY AC 22 366 1257 12 1 PUSH BUTTON GRAY GND REV JUL 1974 7 1 Mechanical Parts List 5A21N Fig amp Index No 1 23 24 25 26 27 28 23 30 31 32 33 34 39 36 37 38 39 40 41 42 43 44 45 46 47 48 49 250 x 52 53 54 55 56 DT 58 99 60 61 62 Tektronix rt No 366 1257 13 366 1257 111 366 1257 12 366 1257 14 384 1059 00 136 0429 00 337 1430 00 213 0254 00 366 0493 00 213 0153 00 366 1295 00 213 0153 00 333 1388 00 386 1914 00 337 1396 00 426 0725 00 213 0229 00 337 1399 00 426 0724 00 213 0229 00 670 1344 00 670 1344 01 388 1903 00 131 0566 00 136 0235 00 214 0579 00 260 1209 00 361 0383 00 ma m en LA ga 210 0583 00 210 0046
20. 8 315 0103 00 R280 315 0331 00 R281 316 0102 00 R282 315 0331 00 R283 321 0251 00 R284 315 9331 00 R285 315 0331 00 R286 321 0280 00 R288 316 0392 00 R289 316 0181 00 SWITCHES SIA SiB sic 260 1210 00 Sib SLE S180 260 1209 00 S240 105 0293 00 259 260 1208 00 Electrical Parts List 5A21N Serial Model No Dscont Description 20 OHM 0 125W PREC 0 25 2K OHM 0 125W PREC 1 2 49K OHM 0 125W PREC 19 1 1K OHM 0 125W PREC l1 15K OHM 0 125W PREC 1 15K OHM 0 125W PREC 1 2 61K OHM 0 125W PREC 1 15K OHM 0 25W 5 6 65K OHM 0 125W PREC 1 100 OHM VAR IK OHM 0 25W 806 OHM 0 125W PREC 1 10K OHM 0 25W 5 330 OHM 0 25W 5 lK OHM 0 25W 330 OHM 0 25W 5 4 02K OHM 0 125W PREC 1 330 OHM 0 25W 5 330 OHM 0 25W 5 8 06K OHM 0 125W PREC 1 3 9K OHM 0 25W 180 OHM 0 25W PUSH BUTTON PRE AC PUSH BUTTON CHG GND PUSH BUTTON CURR PROBE ONLY PUSH BUTTON PRE AC PUSH BUTTON CHG GND PUSH BUTTON DISPLAY ON CAM ACTUATOR ASSY VOLTS DIV OR AMPERES DIV PUSH BUTTON BANDWIDTH LIMIT 10 KHZ lsee Mechanical Parts List for replacement parts REV JUL 1974 5 5 5A21N SECTION 6 DIAGRAM AND CIRCUIT BOARD ILLUSTRATION Symbols and Reference Designators Electrical components shown on the diagrams are in the following units unless noted otherwise Capacitors Values one or greater are in picofarads pF Values less than one are in microfarads uF Resistors Ohms 9 Symbo
21. 96 in the attenuation factors of the input attenuators may reduce the rejection ratio to 10 000 1 Likewise any difference in source impedance at the two points in the source under test will degrade the rejection ratio Attenuator probes which do not have adjustable R and C may reduce the rejection ratio to 100 1 or less Outside influences such as magnetic fields can also degrade the performance particularly when low level signals are involved Magnetic interference may be mini mized by using identical signal transporting leads to the two inputs and twisting the two leads together over as much of their length as possible 2 5 Operating Instructions 5A21N Double exposure photographs of the waveforms applied to the SEW WEES ZW KE Photographs of the resultant display E LLL ARE 2 B a L ELELEUELE baba E A composite waveform of a desired signal square wave with an interfering line frequency component is applied to the input The interfering signal sine wave is also applied to the input connector NOTE The waveform of the signals applied to the input connectors will appear inverted when viewed alone _ Fig 2 2 Three examples of differential applications Voltage Probes In general probes offer the most convenient means of connecting a signal to the input of the 5A21N Tektronix probes are shielded to prevent pickup of electrostatic inter ference A 10
22. Al CH t mp bm 8 Min HE Asi GST EHE Ae o rh i 0 ME DECK ASI OO ME EZ Gezo sza wgl cap 4es 914 v5 i HVA Zug 3 Al pir Kos 6 Y H Z Moi 9 OLD 1 7 LA bite v EOD NE 900 He Ob LA KKH VEY C gia T9 AOE UBI V Awe SIA OBIS i Qoi i ONIS SATIOA Pl 10 0 951 9 CE YA od P MEZI H O ZHAO 008 Obi Se Limia yr Pritt 7 VS kS HAKMONYS N Y NAL esz vesio Sol Adoz 2 21 Zu 2 coz Bun TY Oza 5 0 89 POSU Qa AZ TE Grid AS Gi im e 1 Opis NIZWS AS AZ i AS O e Ae AMOS ADR nez CAE gt pii e edv xi Aq YANN 332 E bg 2 SA ONISN3FS DAGMA HAAA HOLININODIHNAIS 23034 Lait Q Aaa uae ILON 5A21N MECHANICAL PARTS LIST Replacement parts shouid be ordered from the Tektronix Field Office or Representative in your area Changes fo Tektronix products give you the benefit of improved circuits and components the instrument type number and serial number with each order for parts or service Please include ABBREVIATIONS BHB binding head brass h height or high OHB oval head brass BHS binding head steel hex hexagonal OHS oval head steel CRT cathode ray tube HHB hex head brass PHB pan head brass csk countersunk HHS hex heqd steel PHS pan head steel DE dou
23. INSTRUCTION MANUAL Tektronix Inc P O Box 500 8 Beaverton Oregon 97005 Phone 644 0161 Cables Tektronix 070 1139 00 271 SECTION 1 SECTION 2 SECTION 3 SECTION 4 SECTION 5 SECTION 6 SECTION 7 TABLE OF CONTENTS SPECIFICATION Introduction Table 1 1 Electrical Characteristics Table 1 2 Environmental Characteristics OPERATING INSTRUCTIONS Plug in Insertion and Removal Controls and Connectors First Time Operation Preparation Step Attenuator Balance Adjustment Gain Check General Operating Information Applying Signals Signal Input Connectors High Impedance Input Display Polarity Deflection Factor Voltage Comparison Measurements Differential Operation Voltage Probes Current Probes CIRCUIT DESCRIPTION Biock Diagram Description Detailed Circuit Description Plug in Logic Input Coupling Current Probe Amplifier Input Attenuators Input Protection Preamplifier Stage Common Mode Rejection Isolation Stage Output Amplifier Trigger Signal Amplifier Vertical Switching and Readout CALIBRATION Services Available Using This Procedure f Test Equipment Required Preliminary Control Settings Part Performance Check Part tl Adjustment ELECTRICAL PARTS LIST DIAGRAMS f Symbols and Reference Designators Schematic Diagrams and Component Board Locations MECHANICAL PARTS LIST SA21N Page 1 1 1 1 2 1 2 1 2 2 2 2 2 3 2 3 2 3 2 3 2 4 2 4 2 4 2 4 2 5 2 6
24. ONNECTORS This is a brief description of the function or operation of the front panel controls and connectors More detailed information is given under General Operating Information DISPLAY ON Applies and removes logic levels to the oscilloscope system to enable or disable plug in operation Switch is functional only when plug in is operated in one of the vertical plug in compartments POSITION BANDWIDTH LIMIT VOLTS DIV AMPERES DIV Variable Volts Div or Amperes Div STEP ATTEN BAL CURR PROBE ONLY Input Coupling Pushbuttons 5A21N Positions display Alows reduction of the upper bandwidth limit to increase the signal to noise ratio for low frequency applications Selects upper bandwidth limit at either 1 MHz button out or 10 kHz button in Volts or amperes per major grati cule division Selects calibrated deflection factor in a 1 2 5 se quence from 50 LV Div to 5 V Div in 16 steps or from 0 5 mA Div to 0 5 A Div in 10 steps deflection factor uncalibrated from 1 A Div to 50 A Div because of attenuator Knob skirt is illumi nated to indicate deflection factor and X10 scaling of readout is pro vided automatically when a 10X coded probe is used Provides uncalibrated continuously variable deflection factor between calibrated steps extends range to 12 5 V Div or 1 25 A Div Balances the input amplifier for minimum trace shift throughout the deflection factor gain switching range B
25. TS 78 213 0048 00 Ll SETSCREW 4 40 X 0 125 INCH HSS s kw ow ATTACHING PARTS 79 213 0146 00 4 SCREW THERAD FORMING 6 X 0 313 INCH PHS 80 210 0590 00 l NUT HEX 0 375 32 X 0 312 INCH 81 210 0978 00 J WASHER FLAT 0 375 ID X 0 50 INCH OD 82 358 0029 00 1 BUSHING oum lt STANDARD ACCESSORIES 070 1139 00 1 MANUAL INSTRUCTION O REV JUL 1974 7 3 5A21N o SES DA FIGURE 1 EXPLO DED 0030 avd 1891 dv 2 ANG 10044 dv ON 3NWvud N e com sepnjoui Ajqusasse 2 uogdi19seg 1 9 389 NOLYVO L s t CZ os G 3 1 ON OI Eug 0 00 1SL0 S90 ON 342d 1 8 388 075 00 1 0 00 0 00 0 00 0 00 0 0 00 0 ON Hed XIUO41319 L ON xapu m Bi umous JOU uOnonJdisut AVANVIN L 0066 s v Z L ostq H3 on 58 Ow gt 70075 1 0 83100883007 00 11 040 ON Hed XIUOAPHO L Z ON xepu m dig NL VS 03 01 211 5 2 MANUAL CHANGE INFORMATION At Tektronix we continually strive to keep up with latest electronic developments by adding circuit and component improvements to our instruments as soon as they are devel oped and tested Sometimes due to printing and shipping requirements we can t get these changes immediately into printed manuals Hence your manual may contain n
26. X attenuator probe offers a high input impedance and allows the circuit under test to perform very close to normal operating conditions Seg your Tektronix Inc catalog for characteristics and compatibility of probes for use with th s system 2 6 Differential Measurement The following adjustment procedure is recommended when preparing to use two Tektronix P6023 probes for differential measurement This probe type does not have the coding feature to be discussed later a Connect one probe for DC coupied single ended input di Obtain a triggered display of an appropriate square wave such as that from a calibrator or square wave generator Adiust the probe DC Atten Calibration control for correct deflection sensitivity then compensate the probe square wave response using the AC Fine Comp adjust and the AC Coarse Comp adiust if necessary b Connect a second probe for DC coupled operation Apply the square wave to both probes at 100 volts peak to peak Free run the sweep and adjust the DC Atten Cali bration of the second probe for maximum low frequency cancellation minimum signal amplitude or elimination of the two trace appearance c Adjust the AC Fine Comp and AC Coarse Comp if necessaty of the second probe to minimize the amplitude of the differential pulses on the displayed trace d The above procedure matches the probes for use at any sensitivity which employs the particular 5A21N input a
27. al deflection Readjust R109 if necessary for best compromise at 100 hertz and one kilohertz Adjustment 5A21N 6 Adjust High Frequency CMRR C221 and C250 a Change the following control settings VOLTS DIV 5V Input Coupling GND b Set the sine wave generator for exactly four divisions of 30 kilohertz display c Set the Input Coupling to DC and the VOLTS DIV switch to 0 1 mV d ADJUST C250 CMRR 2 for one division of vertical deflection Then adjust C221 CMRR 1 for minimum dis play amplitude when switching the VOLTS DIV from 1 mV to 50 mV e CHECK Vertical deflection for all VOLTS DIV switch ranges from 1 mV to 50 mV is two divisions or less Adjust C221 and C250 for best compromise if necessary f Disconnect atl test equipment This completes the Adjustment portion of the Cali bration procedure NOTES NOTES 5A21N ELECTRICAL PARTS LIST Replacement parts should be ordered from the Tektronix Field Office or Representative in your area Changes to Tektronix products give you the benefit of improved circuits and components Please include the instrument type number and serial number with each order for parts or service ABBREVIATIONS AND REFERENCE DESIGNATORS A Assembly separable or repairable AT Attenuator fixed or variable B Motor BT Battery C Capacitor fixed or variable Cer Ceramic CR Diode signal or rectifier CRT cathode ray tu
28. be DL Delay tine DS Indicating device lamp Electrolytic EMC electrolytic metal cased FL H HR J K L LR M Q P Filter PTM Heat dissipating device heat sink etc R Heater RT Connector stationary portion 5 Relay T inductor fixed or variabie TP Inductor resistor combination U Meter Transistor or silicon controlled rectifier Var Connector movable portion VR PMC Paper meta cased paper or plastic tubular molded i Resistor fixed or variable Thermistor Switch Transformer Test point Assembly inseparable or non repairable Electron tube Variable Voltage regulator zener diode etc REV JUL 1974 EMT electrolytic metal tubular PT paper tubular WW wire wound F Fuse Y Crystal Tektronix Serial Model No Ckt No Part No Eff Disc _ Description 1 CHASSIS CAPACITORS C4 295 0142 00 0 1UF MATCHED PAIR C14 BULBS DS182 150 0111 00 NEON AIC DS187 150 01i1 00 NEON AIC CONNECTORS J1 131 0679 00 B010100 BO41688 BNC RECEPTACLE ELECTRICAL gL 131 0679 02 B041689 BNC RECEPTACLE ELECTRICAL Jil 131 0679 00 B010100 280410688 BNC RECEPTACLE ELECTRICAL J113 131 0679 02 B041689 BNC RECEPTACLE ELECTRICAL J21 131 0955 00 BNC RECEPTACLE ELECTRICAL RESISTORS R179 311 0310 01 B010100 B039999 5K OHM VAR R179 311 1368 00 B040000 5K OHM VAR MAIN CIRCUIT BOARD ASSEMBLY 670 1344 00 BO10100 B039999 COMPLETE BOARD 670 1344 01 B040000 COMPLETE BOARD CAPACITORS cl 28
29. ble end HSB hex socket brass RHS round head steel FHB flat head brass HSS hex socket steel SE single end FHS flat head steel ID inside diameter THB truss head bross FH HB fillister head brass lg length or long THS truss head steel FH HS filister head steel OD outside diameter w wide or width FIGURE 1 EXPLODED Fig amp index Tektronix Serial Model No _ No Part No Eff Dscont Qty 1 2 s 45 Name amp Description 1 1 366 0494 00 L KNOB GRAY POSITION 213 0153 00 l SETSCREW 5 40 X 0 125 INCH HSS _ ws RESTSTOR VARIABLE ATTACHING PARTS 3 210 0583 00 1 NUT HEX 0 25 32 X 0 312 INCH 4 210 0940 00 i WASHER FLAT 0 375 ID X 0 50 INCH OD Lo d ms ur dni uw 5 131 0679 00 8010100 B041688 2 CONNECTOR RECEPTACLE 3 CONTACT BNC 131 0679 02 B041689 2 CONNECTOR RECEPTACLE 3 CONTACT BNC ATTACHING PARTS FOR EACH 220 0497 00 XB041689 i NUT PLAIN HEX 0 095 X 0 562 INCH 210 1039 00 XB041689 1 WASHER LOCR INT 0 521 ID X 0 625 INCH OD Le ei 129 0103 00 1 BINDING POST ASSEMBLY 6 129 0077 00 l STUD 7 200 0103 00 a CAP ATTACHING PARTS 8 210 058 3 00 1 NUT HEX 0 25 32 X 0 312 INCH 9 2 210 004 6 0 1 WASHER LOCK INTERNAL 0 261 ID X 0 40 INCH OD 9 ee 10 131 0955 00 l CONNECTOR RECEPTACLE BNC FEMALE lt 11 366 1036 01 1 KNOB GRAY ATTEN STEP BAL 12 384 1065 00 1 SHAFT EXTENSION 3 485 INCHES LONG 13 376 0051 00 B010100 8039999 l COUPLING 376 005i1 01 B040000 1 COUPLING 213 0022 00 B010100 8039999 4 SETSCREW 4
30. c K Relay Y Crystal L inductor fixed or variable 2 6 1 vv c e ze Ely LW 313 Sit 6 g7 UO 9820 0820 A Ye LOO ue9 Ua Ses vasto ES Tat ANZ uHOS o42 0 OLD ANSYUND SNINOLLISOd 64l Saz D 910 098 D 0915 tosio vos 36210 90 Bla ia MALMO Sidi dyWwYaNc NIYO vA 9 40 O 1D O ID S d ONILWOTS ONIHDLIAAS 2907 N1 90714 weern We ail DA OOS OC D GED AW v 2 0 di ANA ROD acow 3 ONITdOAOD HOLVANALLY Loan ya ANAE Oi i Xi zaMOod dwva L 481 810 1 2 8 A 1008 Bal NO AN estia ogi s NI Z ws we 39044 03009 39044 NANL SE TA 012 ea z92H va Gul 8 L LH v iviH M OLH ECO 0920 gr ero ET 1019 SH 6828 vO 892H v 0ZZH C8 OZLH Fa OriH br 0014 ZY 810 ZH oO SH 80 v8 va ISCH a tiza 3 o 6098 SG EiB SI zou zr 80 vo 92 LED va 98z4 Sa 9szH s0zd ea sau sa sStiH ocu 29 040 v8 4829 va 82 982 g9 SscH v3 Su EI 90zH O L9LH SG iciul SH sey ed g g tezol 73 0859 en SEI v8 v8cH c3 escu ZT cozy a Zou v9 ein SH seu EQ 090 F3 6riun sa 6 20 6p2 99 SEH CH 82H r Leni GI ooeul vo een 9 ozlul oi Seu ra SA mal SO sezo sa 8bto 222 co 5685 8 Z82H VA 6vcH ZY oul O seul SziH 9D
31. ching current from DS182 to DS187 When the instrument is operated in the CURR PROBE ONLY mode DS187 is illuminated to indicate the vertical deflection factor in units of amperes per division 5A21N SECTION 4 CALIBRATION Change information if any affecting this section will be found at the rear of this manual Introduction Before complete calibration thoroughly clean and inspect this instrument as outlined in the Maintenance section of the Oscilloscope System manual Services Available Tektronix Inc provides complete instrument repair and recalibration at local Field Service Centers and at the Factory Service Center Contact your local Tektronix Fieid Office or representative for further information Using This Procedure General This section provides several features to facili tate checking or adjusting the 5A21N These are Index To aid in locating a step in the Performance j Check or Adiustment procedure an index is given pre ceding Part Performance Check and Part Il Adjust ment procedure Performance Check The performance of this instru ment can be checked without removing the covers or mak ing internal adjustments by performing only Part Performance Check This procedure checks the instru ment against the tolerances listed in the Performance Requirement column of Section 1 Also a reference is made to the step in Part Adjustment which will return the instrument to t
32. current probe transformers with 125 turn secondary windings No special preparation of the 5A21N is required Connect the probe to the 125 TURN PROBE connector and select the CURR PROBE ONLY mode of instrument operation Refer to the current probe manual for probe details 2 7 uw HA Deeg z 5A21N SECTION 3 CIRCUIT DESCRIPTION Change information if any affecting this section will be found at the rear of this manual introduction This section of the manual contains an electrical descrip tion of the circuits in the 5A21N Differential Amplifier unit Complete schematic diagrams and an overall biock diagram of the unit are given on pullout pages at the back of this manual BLOCK DIAGRAM DESCRIPTION When the DISPLAY ON button is pressed a logic tevel is applied to the oscilloscope to enable 5A21N operation switch function is limited to operation in a vertical com partment and the front panel readout lamp illuminates to indicate the ON mode Voltage signals applied to the and input connectors can be passed directly to the attenuators DC coupled or they can be capacitively AC coupled to block the DC component of the signal The GND switch disconnects DC coupled signals and applies a reference ground to the preamplifier input for AC coupled signals the coupling capacitor is allowed to pre charge to the DC level of the signal preventing a damaging current surge when the ground is r
33. d prepare the instrument for immediate use The remainder of the steps demonstrate some of the basic functions of the 5A21N Operation of other instruments in the system is described in the instruction manuals for those units 1 insert the unit all the way into the oscilloscope system plug in compartment 2 Turn the oscilloscope Intensity control fully counter clockwise and turn the oscilloscope system Power On Pre set the time base and triggering controls for a 2 millisecond division sweep rate and automatic triggering 3 Set the 5A20N front panel controls as follows DISPLAY POSITION BANDWIDTH LIMIT 1 MHz button out CURR PROBE ONLY VOLTS button out VOLTS DIV ON readout illuminates Midrange STEP ATTEN BAL Midrange Input Coupling DC GND Input Coupling DC GND 2 2 NOTE About five minutes is sufficient time for warmup when using the 5A21N for short term DC measure ments For long term DC measurements using the lower deflection factors allow at least 15 minutes 4 Adjust the Intensity control for normal viewing of the trace The trace should appear near the graticule center 5 Move the trace two divisions below the graticule centerline with the POSITION control LR d CAUTION MSA If the maximum input voltage rating at the gates of the input FET s is exceeded the gates are diode clamped at about or 12 5 volts If the signal source can supply more than 1 16 A the inp
34. e BANDWIDTH LIMIT 10 kHz switch places a capaci tor across the two output lines to reduce the bandwidth and thus limit the noise referred to the input The signal is then passed through an emitter follower isolation stage to the output amplifier The output differential amplifier is operated push puil presenting a signal to the output terminals of the same polarity as that applied to the preamplifier input Emitter degeneration produced by the Variable Volts Div and Gain controls provides a means of varying the gain of the 5A21N A positioning current driver is connected to the output lines to alter the quiescent CRT beam position A triggering signal is tapped from the emitter follower isolation stage amplified and made available to an associ ated time base plug in unit Triggering signal amplitude is about 0 25 volt per displayed division DETAILED CIRCUIT DESCRIPTION Plug In Logic When the DISPLAY ON button 180 is pressed a logic level is applied to the electronic switching circuit in the oscilloscope to enable plug in operation Power is applied to illuminate the front panel knob skirt readout lamp indi cating the ON mode Input Coupling Signals applied to the front panel and input con nectors may be capacitive coupled AC direct coupled DC or internally disconnected GND Input coupling is selected by means of two pushbutton switches at each input STA and S1B for the input and S1D and STE for the
35. e kilo hertz g CHECK Vertical deflection is 0 2 division or less 6 Check High Frequency CMRR a Set the sine wave generator for a 20 volt 30 kitohertz output set the VOLTS DIV switch to 5 V Input Coup ling to GND and obtain exactly four vertical divisions of display b Set the Input Coupling to DC and the VOLTS DIV switch to 50 mV c CHECK Vertical deflection for all VOLTS DIV switch ranges from 50 mV to 1 mV is two divisions or less for 50 UV four divisions or less d CALIBRATION 1f more than two divisions of verti cal display are present at these ranges perform step 6 of the Adjustment procedure 7 Check Amplifier Bandwidth a Set the sine wave generator for minimum output amplitude b Change the controls as follows VOLTS DIV AV Input Coupling AC Input Coupling GND Seconds Div time base ms c Adjust the sine wave generator for eight vertical divi sions of one kilohertz display as a reference Then slowly increase the frequency until the display amplitude is 5 66 divisions This is the upper 3 dB point Performance Check 5A21N d CHECK Frequency at the upper 3 dB point must be at least one megahertz e Set the BANDWIDTH LIMIT to 10 kHz button in and adjust the sine wave generator for eight vertical divi sions of 2 kilohertz reference display Then slowly increase the frequency until the display amplitude is 5 66 divisions f CHECK Fr
36. ements on the two sides of the amplifier were matched e g O120A and 01208 transconductance and Q129A and Q129B beta current sources etc In practice any mismatch will cause a differential output Floating Power Supply A floating power supply made up of Q130 0140 Q146 and Zener diodes VR 148 and VR149 minimize inherent common mode difficulties and therefore improves the common mode rejection ratio refer to Fig 3 2 0146 is a constant current high impedance source for Q140 and 0130 is the current return for the preamplifier stage Circuit Description 5A21N Constant Current Source 0130 Constant f Current Return 01584 0158B Current Return 0146 Fig 3 2 Floating Power Supply detailed block diagram showing standing current paths through the Preamp The input to the bootstrap X1 gain amplifier is con nected to the junction of R140 and R141 The bootstrap amplifier portion of the supply consists of emitter follower 0140 and DC level shifting Zener diodes VR148 and VR149 The collector impedance of O146 presents mini mum loading to the 0140 output and maintains the gain of the amplifier bootstrap efficiency very close to one The entire power supply and amplifier voltages move an amount equal to the common mode voltage maintaining a constant operating characteristic of the elements in the pre amplifier stage Since no signal current is developed the output at the collectors of Q150A and O150B
37. emoved A current signal applied via a 125 turn probe is AC coupled to the preamplifier input when the CURR PROBE ONLY button is pressed The signal is also applied to a feedback amplifier which compensates the probe characteristics The compensated signal is then AC coupled to the preamplifier input The input attenuators are frequency compensated volt age dividers 1X attenuation is provided for positions 50 uV to 50 mV of the VOLTS DIV switch and 100X attenu ation is provided for positions 0 1 V to 5 V Balance to a low frequency common mode signal between the attenu ators of the two inputs is set by adjustment of the LF CMRR potentiometer From the input attenuators the signal is passed directly to the preamplifier The inputs to the preamplifier are fuse and diode protected The preamplifier consists of two identical operational amplifiers connected in a differential configuration Common mode signals between ground and the two inputs are rejected due to a bootstrapped floating power supply that moves with the common mode signal to maintain constant operating characteristics of the active devices The difference between the two inputs is amplified The VOLTS DIV switch changes the value of the common source emitter resistor between the two sides thus chang ing the gain for various deflection factors The output of the preamplifier stage is a push pull signal opposite in polarity to that applied to the input Th
38. equency at the upper 3 dB point band width limited is between 8 kHz and 12 kHz g Release the BANDWIDTH LIMIT switch button out and adjust the sine wave generator for eight vertical divi sions of 2 kilohertz reference display Then slowly decrease the frequency until the display amplitude is 5 66 divisions This is the lower 3 dB point when AC coupling is used determined by the coupling capacitor Set the time base Seconds Div as necessary to view the signal h CHECK Frequency at the lower 3 dB point is two hertz or less i Disconnect the sine wave generator 8 Check Input Gate Current a Position the trace to the graticule center then change the following control settings VOLTS DIV 50 uV Input Coupling AC GND Input Coupling AC GND Seconds Div time base 1 ms b Connect a 50 ohm termination to the input con nector and using the STEP ATTEN BAL control position the trace to the graticule centerline c Release the GND button of the Input Coupling switch input AC coupled d CHECK Trace shift is less than 2 divisions This indicates an FET gate current of 100 picoamperes or less e Ground the Input Coupling GND button in and move the 50 ohm termination to the input connector f Release the GND button of the Input Coupling switch Performance Check 5A21N g CHECK Trace shift is less than 2 divisions h Remove the 50 ohm termination 9 Check Overal N
39. ew change information on following pages single change may affect several sections Sections of the manual are often printed at different times so some of the information on the change pages may already be in your manual Since the change information sheets are carried in the manual until ALL changes are permanently entered some duplication may occur If no such change pages appear in this section your manual is correct as printed
40. f screen start at the position of the VOLTS DIV switch at which an on screen display is obtained and adjust R227 Coarse DC Bal working down to the 50 UV position so the trace remains on screen at 50 UV Make the fine adjustment to bring the trace to screen center with the front panel STEP ATTEN BAL control Maximum allowable shift of trace is one division as the VOLTS DIV switch is rotated 3 Adjust Amplifier Gain R268 a Connect the standard amplitude calibrator output connector to the input connector through a coaxial cable Set the standard amplitude calibrator for a 5 millivolt square wave output b Set the VOLTS DIV switch to 1 mV and release the input Coupling GND button out c ADJUST R268 Gain for a display amplitude of exactly five divisions 4 8 4 Adjust Input Compensation C1 C2 C3 C11 C12 C13 a Set the VOLTS DIV switch to 1 V b insert a 47 pF input RC normalizer between the signal cable and the input connector c Set the standard amplitude calibrator for a 1 voit square wave output five divisions displayed d ADJUST C1 and C2 for minimum roll off or over shoot of leading corner of square wave display e Set the standard amplitude calibrator for a 5 volt square wave output and change the VOL TS DIV switch to 50 mV f ADJUST C3 for minimum roll off or overshoot of leading corner of square wave display g Move the RC normalizer and calibrator signal from the input t
41. g circuit incorporated in the unit The pre charging circuit permits charging the coupling capacitor to the DC source voltage when the AC and GND buttons are pressed in The procedure for using this circuit is as follows a Before connecting the BA21N to a signal containing a DC component push in the AC and GND buttons Then connect the input to the circuit under test b Wait about one second for the coupling capacitor to charge Operating Instructions 5A21N c Remove the ground from the coupling capacitor GND button out The display will remain on screen and the AC component can be measured in the usual manner The above procedure should be followed whenever a sig nal having a different DC level is connected CAUTION lf the 5A21N input is connected to a large DC voltage source without using the pre charge provision the peak charging current into a 0 1 uF capacitor will be limited only by the internal resistance of the signal source and this source may be damaged Signal Input Connectors When connecting signals to the and input connectors on the 5A21N consider the method of coupling that will be used Sometimes unshielded test leads can be used to connect the 5A21N to a signal source particularly when a high level low frequency signal is monitored at a low impedance point However when any of these factors is missing it becomes increasingly important to use shielded signal cables In all cases t
42. gnals is arnpli fied and displayed in differential measurements while the common mode signals common in amplitude frequency and phase are rejected See Fig 2 2 The ability of the 5A21N to reject common mode sig nats is indicated by the common mode rejection ratio CMRR CMRR is at least 100 000 1 at the input con nectors for the ower deflection factors 50 and 100 UV DIV when signals between DC and 30 kHz are DC coupled to the inputs To illustrate this characteristic assume that a single ended input signal consists of an unwanted 60 Hz signal at 1 volt peak to peak plus a desired signal at 1 mV peak to peak If an attempt is made to display the described signal single ended measurement at 2 mV DIV the 60 Hz signal will produce a deflection equivalent to 5000 divisions and the 1 mV signal wiH be lost If the same 1 mV signal is measured differentially with the 60 Hz signal common to both inputs no more than one part in 100 000 of the common mode signal will appear in the display The desired signal will produce a display of 5 divisions with not more than 0 1 division of display pro duced by the common mode signal CMRR not specified when residual display is 0 1 division or less There are a number of factors which can degrade common mode rejection The principal requirement for maximum rejection is for the common mode signal to arrive at the input FET gates in precisely the same form A differ ence of only 0 01
43. he correct calibration In most cases the adjustment step can be performed without changing control settings or equipment connections Adjustment Procedure To return this instrument to correct calibration with the minimum number of steps per form oniy Part if Adjustment The Adjustment pro cedure gives the recommended calibration procedure for all circuits in this instrument Procedures are not given for checks which can be made without removing the covers see Part Performance Check for the correct procedure for making these checks Complete Performance Check Adjustment To com pletely check and adjust all parts of this instrument per form both Parts and Il Start the complete procedure by removing instrument covers as outlined in the Preliminary Procedure of Part i1 Adjustment Then follow the Per formance Check referring to the Adjustment procedure as directed to make the actual adjustments This method will ensure that the instrument is both correctly adjusted and performing within all given specifications TEST EQUIPMENT REQUIRED General The following test equipment and accessories or its equivalent is required for complete calibration of the 5A21N Specifications given for the test equipment are the minimum necessary for accurate calibration Therefore some of the specifications listed here may be somewhat less r gorous than the actual performance capabilities of the test equipment Ail test equ
44. he signal transporting leads should be kept as short as practical When making single ended input measurements conven tional amplifier operation be sure to establish a common ground connection between the device under test and the 5A21N The shield of a coaxial cable is normally used for this purpose in some cases differential measurements require no common ground connection and therefore are less suscep tible to interference by ground loop currents Some prob lems with stray magnetic coupling into the signal transporting leads can also be minimized by using a differ ential rather than a single ended measurement These con siderations are discussed later in this section under Differ ential Operation It is always important to consider the signal source load ing and resulting change in the source operating character istics due to the signal transporting leads and the input circuit of the 5A21N The circuit at the input connectors can normally be represented by a 1 megohm resistance to ground paralleled by about 47 pF A few feet of shielded rhe DC plus AC voltages on the test points with respect to the chassis potential of the 5A21N should be limited to the levels listed in Section 1 under Maximum Common Mode Input Voltage charac teristics Higher levels will degrade the common mode rejection ratio and exceed the input voltage rating of the unit 2 3 Operating Instructions 5A21N cable 20 to 40 pF per foot may
45. i tudes since the deflection factor is restricted to 50 mV div through 50 uV div and DC coupling must be used NOTE In the 0 1 V to 5 V range of the VOLTS DIV switch the input impedance is paralleled by the resistors in the attenuator When the link is removed the attenu ation ratio is affected causing the deflection factors in this range to be incorrect To determine the deflec tion factor check the deflection with an input signal of known amplitude The signal source impedance is an important factor since gate current will produce a DC offset For example a 100 picoampere gate current through 10 megohms pro duces a one millivolt offset which may result in significant error where small voltages are of concern The high frequency response will aiso depend upon the signal source impedance since various shunt capacitances 2 4 between the source and the input gate must charge and discharge through that impedance Display Polarity Single ended signals applied to the input connector produce a display in phase with the input signal Signals applied to the input connector will be inverted A similar polarity relationship exists for differentially applied signals but it pertains to the direction of voltage change at one input with respect to the other rather than with respect to chassis potential Deflection Factor The amount of trace deflection produced by a signal is determined by the signal amplitude the a
46. ipment is assumed to be correctly calibrated and operating within the listed specifications The Performance Check and Adjustment procedures are based on this recommended equipment 1f other equipment is substituted control settings or calibration setup may need to be altered to meet the requirements of the equip ment used Detailed operating instructions for the test equipment are not given in this procedure Refer to the instruction manual for the test equipment if more informa tion is needed Special Calibration Fixtures Special Tektronix calibration fixtures are used in this procedure only where they facilitate instrument calibration These special calibration fixtures are available from Tek tronix inc Order by part number through your loca Tektronix Field Office or representative Calibration Equipment Alternatives All of the test equipment is required to completely check and adjust this instrument However some of the items used only for the Performance Check can be deleted without compromising the measurement capabilities of the instrument Test Equipment 1 5100N series oscilloscope For this procedure a 5103N D 10 with a 5B TON time base is used 4 1 Calibration 5A21N 2 Standard amplitude calibrator Output signal one kilohertz square wave output amplitude 2 millivolt to 100 volts amplitude accuracy within 0 25 must have a 5 milliampere current loop Tektronix calibration fixture 067 0502 01 reco
47. its range Readjust the POSITION control if necessary to return the trace to graticule center after mini mum shift has been attained c CALIBRATION If balance cannot be achieved center the STEP ATTEN BAL control and perform step 2 of the Adjustment procedure 3 Check Amplifier Gain and VOLTS DIV Switch Accuracy AMPLIFIER GAIN a Connect the standard amplitude calibrator output connector to the input connector through a coaxial cable Set the standard amplitude calibrator for a B millivolt square wave output b Set the VOLTS DIV switch to 1 mV and release the Input Coupling GND button out c CHECK Display amplitude is five divisions X 0 1 divi sion Adjust positioning as required 4 3 Performance Check 5A21N d CALIBRATION Ir amplitude is out of the specified tolerance perform step 3 of the Adjustment procedure VOLTS DIV ACCURACY e CHECK Using the VOLTS DIV switch and standard amplitude calibrator switch settings given in Table 4 1 check the VOLTS DIV switch accuracy Set the BAND WIDTH LIMIT switch to 10 kHz for the more sensitive positions TABLE 4 1 VOLTS DIV Switch Standard Amplitude CRT Display Setting Calibrator Output Vertical Deflection 5 Y 4 div 0 08 div 2 V 5 div 20 1 div tV 5 div 0 1 div 5 V 4 div 0 08 div 5 div 01 div AV 5 div 0 1 div 50 mV 4 div 0 08 div 20 mV 5 div 0 1 div 10 mV 5 div 0 1 div Connect a 1000 1 divider between the cali brator o
48. just the sine wave generator for eight vertical divi sions of 2 kilohertz reference display Then slowly decrease the frequency until the display amplitude is 5 66 divisions This is the lower 3 dB point Set the time base Seconds Div switch as necessary to view the signal h CHECK Frequency is 15 hertz or less i Disconnect all test equipment This completes the Performance Check portion of the Calibration procedure Adjustment 5A21N PART I ADJUSTMENT Introduction The following procedure returns the 5A21N to correct calibration All limits and tolerances given in this procedure are calibration guides and should not be interpreted as instrument specifications except as given in Section 1 of this manual The actual performance of the instrument may exceed the given limits or tolerances if the instrument meets the Performance Requirements as checked in Part Performance Check of this section Location of internal adiustments is shown in Fig 4 1 Index to Part II Adjustment Page 1 Adiust Variable Balance R159 4 8 2 Adjust DC Balance R227 4 8 3 Adiust Amplifier Gain R268 4 8 4 Adjust Input Compensation C1 C2 4 8 C3 C11 C12 C13 C250 C221 CMRR1 CMRR 2 R159 Variable Balance 5 Adjust Attenuator Low Frequency 4 9 CMRR R 109 6 Adjust High Frequency CMRR 4 9 C221 and C250 Preliminary Procedure For Adjustment NOTE This instrument should be adjusted at an ambient
49. justed the CRT zero reference point trace or spot will shift vertically due to differential DC imbalance in the amplifier as the VOLTS DIV switch is rotated throughout its range The shift is more noticeable on the most sensitive positions a With the instrument operating ground both the and inputs GND buttons pushed in set the VOLTS DIV switch to 5 V and move the trace to graticule center with the POSITION control b Adjust the STEP ATTEN BAL control for minimum trace shift as the VOLTS DIV switch is rotated throughout its range Gain Check Whenever the 5A21N is inserted into a plug in compart ment other than the one in which it was calibrated the amplifier gain may be checked and if necessary adiusted _ See the Calibration Procedure in this manual for complete instructions GENERAL OPERATING INFORMATION Applying Signals When measuring DC voitages use the largest deflection factor 5 V Div when first connecting the 5A21N to an unknown voltage source ff the deflection is too small to make the measurement switch to a lower deflection factor If the input stage is overdriven a large amount of current might flow into the input and open the protective fuse See CAUTION after item 5 of the First Time Operation Pre charging When only the AC component of a signal having both AC and DC components is to be measured use the Input Coupling switches AC and GND pushbuttons to take advantage of the pre chargin
50. lifier input Input Attenuators The input attenuators are frequency compensated volt age dividers which provide 100X attenuation in positions 0 1 to 5 of the VOLTS DIV switch At DC and for low frequency signals the dividers are essentially resistive attenuation ratio determined by the resistance ratio Balance to a low frequency common mode signal between the attenuators of the two inputs is set by adjustment of R109 LF CMRR At higher frequencies the capacitive reactance becomes effective and the attenuation ratio is determined by the impedance ratio in addition to providing constant 100X attenuation at all frequencies within the bandwidth capabilities of the instrument the input attenuators maintain a constant input RC characteristic one megohm paralleled by about 47 pF for settings 0 1 to 5 of the VOLTS DIV switch Input Protection Input protection consists of fuses F20 F206 and diodes CR111 CR112 CR113 and CR114 If the signal should reach a level sufficient to forward bias one of the protec 3 2 tion diodes a potential greater than about 12 5 volts cur rent will be conducted through that diode protecting the input FET s If that current should exceed the I T rating of de the fuse the protective fuse s will open if the signal source is not able to supply enough current to open the fuse damage to the signal source may result Preamplifier Stage The preamplifier consists of two identical
51. ls used on the diagrams are based on USA Standard Y 32 2 1967 Logic symbology is based on MIL STD 806B in terms of positive logic Logic symbols depict the logic function performed and may differ from the manufacturer s data The following special symbols are used on the diagrams E External Screwdriver adjustment External control or connector Clockwise control rotation in direction of arrow Refer to diagram number indicated in diamond Refer to waveform number indicated in hexagon 1 ATT Connection soldered to circuit board Connection made to circuit board with interconnecting pin Blue tint encloses components located on circuit board The following prefix letters are used as reference designators to identify components or assemblies on the diagrams A Assembly separable or repairable circuit board etc LR inductor resistor combination AT Attenuator fixed or variable M Meter B Motor Q Transistor or silicon controlled rectifier BT Battery P Connector movable portion C Capacitor fixed or variable R Resistor fixed or variable CR Diode signal or rectifier RT Thermistor DL Delay line S Switch DS indicating device lamp T Transformer F Fuse TP Test point FL Filter U Assembly inseparable or non repairable integrated H Heat dissipating device heat sink heat radiator etc circuit etc HR Heater V Electron tube J Connector stationary portion VR Voltage regulator zener diode et
52. ment 10 Check Current Probe Amplifier Gain a Change the control settings as follows Volts Amps Mode CURR PROBE ONLY button in AMPERES DIV i mA Seconds Div ims time base 4 6 b Connect a 125 turn current probe P6021 to the 125 TURN PROBE input connector and connect the probe tip to the 5 milliampere current loop of the standard amplitude calibrator Adjust the Triggering Level control for a stable display c CHECK F ive divisions 3 of vertical display 11 Check Current Probe Amplifier Frequency Response a Connect a BNC to GR male adapter to the sine wave generator output Connect a high frequency current test fixture to the adapter Connect the 125 turn current probe to the test fixture b Change the time base Seconds Div switch to 5 ms c Adjust the sine wave generator for eight vertical divi sions of one kilohertz display as a reference Then slowly increase the frequency until the display amplitude is 5 66 divisions This is the upper 3 dB point d CHECK Frequency is at least one megahertz e Set the BANDWIDTH LIMIT to 10 kHz button in and adjust the sine wave generator for eight vertical divi sions of 2 kilohertz reference display Then slowly increase the frequency until the display amplitude is 5 66 divisions f CHECK Frequency at the upper 3 dB point band width limited is between 8 kHz and 12 kHz g Release the BANDWIDTH LIMIT switch button out and ad
53. mmended 3 Constant amplitude sine wave generator Frequency 2 hertz to 2 megahertz output amplitude from about 0 5 volt to 40 volts peak to peak For example General Radio 1310 A Oscillator use a General Radio Type 274 OBJ Adapter to provide BNC output Accessories 4 Plug in extension for the 5100N series oscilloscope for adjustment procedure only 5 Coaxial cable impedance 50 ohms length 42 inches connectors BNC Tektronix Part No 012 0057 01 6 Dual input cable Provides matched signal paths to the and inputs BNC connectors Tektronix Calibration Fixture 067 0525 00 recommended 7 Input RC Normalizer RC time constant 47 us 1 MQ X 47 pFY connectors BNC Tektronix Calibration Fixture 067 0541 00 8 In line termination Impedance 50 ohms accuracy 2 connectors BNC Tektronix Part No 011 0049 01 9 1000 1 divider Tektronix Calibration Fixture 067 0529 00 10 10X attenuator 2 needed Impedance 50 ohms accuracy t296 connectors BNC Tektronix Part No 011 0059 01 11 Variable attenuator A variable attenuator that has the end terminals of a 100 ohm potentiometer connected from input to ground and the potentiometer divider arm connects to the attenuator output Tektronix Calibration Fixture 067 051 1 00 recommended 4 2 12 Adapter GR to BNC female Tektronix Part No 017 0063 00 13 Adapter GR to BNC male Tektronix Part No 017 0064 00 14 High frequency curren
54. mperes or less equivalent to 100 microvolts or less depending on external loading at 25 C Maximum Equivalent 4 amperes peak to peak at probe tip with Input POSITION Range Common Mode Rejection DC Direct Coupled AC Capacitive Coupted 50 UV div to 0 5 1 2 125 turn current probe At least 100 dB DC to 30 kilohertz at 50 UV div and 1 mV div with up to 20 1 peak to peak sine wave decreasing by less than 20 dB decade on lower sensitivity ranges up to 50 mV div From 100 mV div to 5 V Div CMRR is at least 50 dB with up to 100 volt peak to peak sine wave CMRR with two P6060 probes is at least 50 dB at any deflection factor At least 80 dB at 5 kilohertz and above decreasing to 50 dB at 10 hertz Supplemental Information 15 hertz or less to 10 kilohertz Within 20 2 or less of pulse amplitude Time constant normalized for 47 microseconds within 3 between channels At least and 10 divisions from graticule center Characteristic Temperature Operating Range Non operating Range Altitude Operating Range Non operating Range Vibration Range Shock Range Specification 5A21N TABLE 1 2 ENVIRONMENTAL CHARACTERISTICS Performance Requirement 0 C to 50 C 55 C to 70 C To 15 000 feet To 15 000 feet To 0 015 inch peak to peak displacement at 50 cycles per second To 30 g s 1 2 sine 11 milliseconds duration 1 3 NOTES
55. ner of the square wave display if roll off or overshoot is objection able perform step 4 of the Adjustment procedure j Set the standard amplitude calibrator for a 5 volt E square wave output and change the VOLTS DIV switch to i 50 mV k CHECK Optimum square leading corner of the square wave display If roll off or overshoot is objection able perform step 4 of the Adjustment procedure t Disconnect the RC normalizer and standard amplitude calibrator 5 Check Attenuator Low Frequency CMRR a Set the controls as follows VOLTS DIV BV and Input Coupling GND Seconds Div time base 5 ms b Connect a dual input cable to the and input connectors Connect a sine wave generator output to the dual input cable through a coaxial cable c Set the sine wave generator for a 100 hertz 40 volt peak to peak reference signal set the Input Coupling to E DC and obtain exactly eight divisions of vertical deflection p d Set the Input Coupling to DC both the and Input Coupling switches should be set to DC and the Y VOLTS DIV switch to 2 V e CHECK Vertical deflection is 0 2 division or less Dis played signal of 40 millivolts 0 2 division or less of a 40 volt signal indicates that CMRR is at least 1000 1 60 dB If vertical deflection is greater than 0 2 division per form step 5 of the Adjustment procedure f Change the sine wave generator frequency to on
56. o that the voltage across the gain setting resistors is zero at all settings of the VOLTS DIV switch This DC balancing is achieved by adjusting R227 Coarse Bal and R 127 STEP ATTEN BAL with the gates of Q120A and 01208 effectively tied together and the VOLTS DIV switch set to 1 mV R159 Var Bal located in the emitter circuit of constant current source transistors O158A and Q158B is adjusted with a zero input signal to set the voltage across the Vari able control R169 in the output amplifier stage to zero volts With both sides of the amplifier so balanced trace deflection is prevented as the Variable control is rotated throughout its range Normally the frequency response of the preamplifier is from DC to at least one megahertz however for low frequency applications where high input sensitivities are used the overall frequency response can be limited to about ten kilohertz to reduce noise referred to the input This is achieved by pushing the BANDWIDTH LIMIT 10 kHz switch S259 which connects C259 across the output of the preamplifier stage Common Mode Rejection One of the primary functions of the preamplifier is to reject any common mode component of the input signal and amplify only the difference Assume that the inputs are tied together and a voltage is applied to the common input The amplifier differential output is ideally zero and would actually be zero provided that the characteristics of all cor responding el
57. o the input h Set the Input Coupling to GND and the Input Coupling to DC Position the display to the center of the graticule area i Set the VOLTS DIV switch to 1 V and set the stand ard amplitude calibrator for a 1 volt square wave output j ADJUST C11 and C12 for minimum roll off or over shoot of leading corner of square wave display k Set the standard amplitude calibrator for a 5 voit square wave output and change the VOLTS DIV switch to 50 mV l ADJUST C13 for minimum roll off or overshoot of leading corner of square wave display m Disconnect the RC normalizer and standard ampli tude calibrator poy 5 Adjust Attenuator Low Frequency CMRR gt R109 a Set the controls as follows VOLTS DIV 5V and Input Coupling GND Seconds Div time base 5 ms b Connect a dual input cable to the and input connectors Connect the sine wave generator output con nector to the dual input cable through a coaxial cable c Set the sine wave generator for a 100 hertz 40 volt peak to peak reference signal set the Input Coupling to DC and obtain exactly eight divisions of vertical deflec tion d Set the Input Coupling to DC both the and Input Coupling switches should now be set to DC and the VOLTS DIV switch to 2 V e ADJUST R109 LE CMRR for minimum deflection Set the sine wave generator frequency to one kilohertz and check for 0 2 division or less of vertic
58. oise Level Tangentially a Connect the standard amplitude calibrator output to the input connector through a BNC to GR adapter a vari able attenuator arrow pointing away from the calibrator output a GR to BNC female adapter a coaxial cable two 10X attenuators and a 50 ohm termination b Set the standard amplitude calibrator for a 2 voit square wave output and turn the variable attenuator control fully clockwise c Change the following control settings Input Coupling DC Input Coupling GND Seconds Div time base 50 us Triggering Level Clockwise time base d Turn the variable attenuator control slowly counter clockwise and observe two noise bands displayed on the CRT noise and free running square wave Continue to turn the variable attenuator control until the two noise bands merge just to the point at which the dark band between the two noise bands disappears e Remove the two 10X attenuators and connect the coaxial cable to the 50 ohm termination f Switch the VOLTS DIV switch to any position that will give a convenient display two traces g CHECK The vertical amplitude of the display Calcu late the tangentially measured noise by dividing the measured display by 100 For example two divisions of display at 5 mV per division is equal to one millivolt One millivolt divided by 100 is equal to 10 microvolts of tangen tially measured noise Maximum noise 30 UV h Disconnect all test equip
59. t test fixture Tektronix Cali bration Fixture 067 0559 00 15 125 turn current measuring probe Tektronix P6051 AC Current Probe recommended Preliminary Control Settings Set the 5A21N and Oscilloscope System controls as follows for both Performance Check and Adjustment pro cedure 5A21N DISPLAY ON readout illuminates when power is on POSITION Midrange BANDWIDTH LIMIT 1 MHz button out CURR PROBE ONLY VOLTS button out VOLTS DIV 50m Variable Volts Div CAL detent fully clockwise STEP ATTEN BAL Midrange Input Coupling DC GND input Coupling DC GND Oscilloscope Mainframe 5103N DM10 Intensity Normal display brightness Focus Adiust for best focus of trace Time Base SB TON Alt button out Display Position Sweep starts at left edge of graticule Seconds Div 1m Variable Seconds Div Cal detent Swp Mag Off button out Triggering Mode Auto Trig AC Coupling Slope Triggering Source Left Triggering Level Midrange Performance Check 5A21N PART I PERFORMANCE CHECK introduction The following procedure checks the performance of the 5A21N without removing the covers or making internal adjustments All tolerances given in this procedure are based on Section 1 Index to Part Performance Check Page 1 Check Variable Balance 4 3 2 Check DC Balance 4 3 3 Check Amplifier Gain and VOLTS DIV 4 3 Switch Accuracy 4 Check Input Compensation 4 4 5 Check Attenuator Low
60. the VOLTS DIV switch can be changed however to accommo date large ratios In doing so regard the numbers which designate the switch positions as ratio factors rather than voltages Fig 2 1 improving s gnal to noise ratio by setting bandwidth A signal applied with the BANDWIDTH LIMIT switch set to 1 MHz B same signal with the BANDWIDTH LIMIT switch set to 10 kHz i Differential Operation Single ended measurements often yield unsatisfactory results because of interference resulting from ground loop currents between the 5A21N and the device under test in other cases it may be desirable to eliminate a DC voltage by means other than the use of a DC blocking capacitor which could limit the low frequency response These limitations of single ended measurements are effectively eliminated using differential measurements Differential measurements are made by connecting each in put input and input to selected points in the test circuit Since the chassis of the 5A21N need not be con nected in any way to the test circuit there are few limita tions to the selection of these test points In any case do Operating Instructions 5A21N not exceed the maximum safe input voltages listed in Sec tion 1 Both Input Coupling switches should be set to the same position AC or DC depending on the method of signal coupling required Only the voltage difference between two si
61. ttenuation factor if any of the probe the setting of the VOLTS DIV switch and the setting of the Variable control The cali brated deflection factors are indicated by the VOLTS DIV switch only when the Variable control is rotated fully clockwise into the detent position The range of the Variable control is at least 2 5 1 It provides uncalibrated deflection factors covering the full f range between the fixed settings of the VOLTS DIV switch The control can be set to extend the deflection factor to at least 12 5 volts division To reduce noise and obtain a more usable display when the VOLTS DIV switch is set to the more sensitive posi tions set the BANDWIDTH LIMIT switch to 10 kHz if this limit does not appreciably distort the desired features of the signal under observation Fig 2 1 shows the improve ment in a displayed one kilohertz signal when the BAND WIDTH LIMIT switch is used Voltage Comparison Measurements Some applications require deflection factors other than the fixed values provided by the VOLTS DIV switch One such application is comparison of signal amplitudes by ratio rather than by absolute voltage To accomplish this apply a reference signal to either input of the 5A21N and set the VOLTS DIV switch and Variable control so that the refer ence display covers the desired number of graticule divi sions Do not change this setting of the Variable control throughout the subsequent comparisons The settings of
62. ttenuator 1X or 100X used in steps b and c When it is necessary to use the other input attenuator steps b and c should be repeated for that attenuator e When examining a small differential signal in the presence of relatively farge common mode components fine adjustment of probe CMRR may be made by tempor arily connecting both probes to either of the two signal sources Operating instructions 5A21N f Movement of the probes should be kept to a minimum after the adjustment Coded Probes The 5A21N is designed for compatibility with coded probes such as the Tektronix P6060 or P6052 1X 10X Passive Probe The and input connectors have an outer ring to which the coding ring on the probe con nector makes contact This type of probe allows the vertical deflection factor indicated by the readout to correspond with the actual voltage at the probe tip eliminating the need to consider the attenuation factor when measuring the signal amplitude on the graticule scale Attenuation on the P6052 probe is selected by a sliding collar on the probe barrel When the collar is pulled back away from the probe tip 1X attenuation is selected when the collar is pushed forward nearest the probe tip 10X attenuation is selected Input resistance for 1X attenuation is 1 megohm for 10X 10 megohms Probe compensation is obtained in the usual manner see probe manual for details Current Probes The current probe input is limited to
63. ut pro tective fuse s will open 6 Apply a 400 millivolt peak to peak signal available at the oscilloscope Calibrator loop through a test lead or 1X probe to the input connector i 7 For DC coupled single ended operation release the GND button associated with the Input Coupling switch The display should be a square wave four divisions in ampli tude with the bottom of the display at the reference estab lished in step 5 Rotate the Variable Volts Div control counterclockwise out of its detent position observing reduction of the display Return the Variable control to the detent CAL position 8 For AC coupled single ended operation re position the display with the POSITION control to place the bottom of the display at the graticule centerline 9 Push in the AC button and note that the display shifts downward about two divisions to its average level 10 Disconnect the coaxial cable from the input con nector Connect a dual input cable to the and input connectors then connect the coaxial cable from the Cali brator to the dual input cable 11 For AC coupled differentia operation set the Input Coupling to AC AC button in GND button out The calibrator signal is now coupled to both inputs as a common mode signal A straight line display should be observed since the common mode signal is being rejected Step Attenuator Balance Adjustment If this control is not properly ad
64. utput and the input connector to check higher sensitivity ranges 5 mV 4 div 0 08 div 2 mV 5 div 0 1 div 1 mV 5 V 5 div 0 1 div 5 mV 4 div 0 08 div 2 mV 5 div 0 1 div 1 mV 5 div 20 1 div 50 4 div 0 08 div f Remove the 1000 1 divider 4 Check Input Compensation a Insert a 47 pF input RC normalizer between the signal cable and the input connector Set the VOLTS DIV switch to 1 V and the BANDWIDTH LIMIT to 1 MHz button out b Set the standard amplitude calibrator for a 1 volt square wave output five divisions displayed c CHECK Optimum square leading corner of the square wave display Aberrations are not to exceed or 2 or 3 overall on any of the checks If roll off or over shoot is objectionable perform step 4 of the Adjustment procedure 44 d Set the standard amplitude calibrator for a 5 volt square wave output and change the VOLTS DIV switch to 50 mV e CHECK Optimum square leading corner of the square wave display If roll off or overshoot is objection able perform step 4 of the Adjustment procedure f Move the RC normalizer and calibrator signal from the input to the input g Set the Input Coupling to GND and the Input Coupling to DC Position the display to the center of the graticule area h Set the VOLTS DIV switch to 1 V and set the standard amplitude calibrator for a 1 volt square wave out put i CHECK Optimum square leading cor
65. utton pushed in selects AMPERES DIV function of the de flection factor switch Enables 125 TURN PROBE input and disables differential voltage input Button out selects VOLTS DIV function of the deflection factor switch Enables differential voltage input and disables current input AC DC Button pushed in selects capacitive coupling of signal applied to associated input connector but ton out selects direct coupling of input signal 2 1 Operating Instructions 5A21N Input Coupling cont Pushbuttons GND Disconnects the input signal and provides ground reference to the amplifier input stage PRE CHG Both AC DC and GND buttons pushed in permits pre charging of the coupling capacitor to the input signal DC level Release GND button for measurement BNC connectors for application of external voltage signals Connector labeled indicates that a positive going signal will cause upward deflection connector labeled indicates that a positive going signal will cause downward deflection Connectors include coded probe input rings for activation of X10 readout and Input Connectors 125 TURN PROBE Connector Provides connection for current probe limited to current probe transformers with 125 turn second ary windings Recommended probe is the Tektronix P6051 FIRST TIME OPERATION Preparation The first few steps of the following procedure are intended to help place the trace on the screen quickly an

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