FM-190 Tuner Service Manual - The Fisher Console Website
Contents
1.2. T Wim X OM Eee om ami y LUE anto dina AMPLIFIER SCHEMATIC 3 i ait 52 HIGH FILTER SW Ji A ne is Tm R45 e V2 Vi v2 Eo 180V ECC83 120 270V t SECTION 1 459 4 T2 a 3880 di 54 aM s one 68 7 295V R2tA RCRDR BOOK gov i OUT c6 259 nia pasg L 3300 Je O2UF Ree 33 R42 IPV 270V nee took 0220 K 00 1 L R50 ELLBO mi 4 AC BAL 6HUS n 2s soo ME 27K BALANCE 412 CONTROL R20 FT amp HIGH FILTER SW orr NER 1 i 100 Q4 SECTION my 5 0 FRONT 1600 V2 Vi i ECC83 1 2 7 j RN T R9 c 295V 820K cls RCROR Q 68 OUT 120K 760 98 A RIS BAS 3300 Ci 33 8 2M 1K lt 2UF R44 12 270 RISB RISB R25 D VS 800K 1 L 22K 80 49 A N TREBLE 220 BAL A SHU8 CHANGER VOLUME CONNECTOR CONTROL 3600 4 POWER M SECTION 2 POWER CONNECTOR NOTE MEASURED WITH VTVM LAST 2 3 VOLTAGE VARIES WITH R36 i2V 3 ALL CAPACITORS NOT MARKED ARE PF UUF A 4 VOLTAGES MEASURED WITH TUNER BW Shr WILL DECREASE SLIGHTLY WITH TUNER arok 04 PIO78 SCHEMATIC BECAUSE ITS PRODUCTS ARE SUBJECT TO CO
3. service Manual FM 190 190 TUNER d FISHER RADIO CORPORATION LONG ISLAND CITY 1 NEW YORK CAUTION This is FISHER precision high fidelity in strument It should be serviced only by qualified personnel trained in the repair of transistor equipment and printed circuitry EQUIPMENT AND TOOLS NEEDED The following are needed to completely test and align modern high fidelity instruments such as amplifiers tuners and receivers Test Instruments Vacuum Tube Voltohmmeter DC VTVM Audio AC Vacuum Tube Voltmeter AC VTVM Oscilloscope Flat to 100 kc minimum Audio Sine wave Generator intermodulation Analyzer Sweep FM Generator 88 to 108 mc Marker Generator Multiplex Generator preferably with RF output FISHER Model 300 or equal Miscellaneous Adjustable Line Voltage Transformer or line voltage regulator Load Resistors 2 8 ohm 50 watt or higher Stereo source Turntable with stereo cartridge or Tape Deck Speakers 2 Full range for listening tests Soldering iron with small diameter tip Fully insulated from power lina PRECAUTIONS Many of the items below are included just as minder they are normal procedures for experienced technicians Shortcuts can be taken but often they cause additional damage to transistors circuit com ponents or the printed circuit board Solde
4. Ungrounded tube shield of V2 zerorcenter dial 22 5 deviation at Through 100K resistor to Test Point 2 L5 and L4 C7 and C6 Adjust for maxi mum negative voltage and check for sinusoidal waveform with scope at LEFT _ or RIGHT output 22 5 deviation Two 120 ohm carbon resistors in series with generator leads to the antenna terminals Figure 1 Through 100K resistor to Test Point 2 Through 100K resistor to Test Point 2 deviation at 400 FROM GENERATOR INS 202 igure 1 Method of connecting resistors series ith generator leads Test Point 4 te ground Figure 2 Typical sweep alignment response curves obtained with properly aligned IF amplifier CHASSIS LAYOUT Tuner i a INDICATOR AMPLIFIER R4 EM84 OSCILLATOR E SEPARATION 16 JH T 19 KC PILOT AND SIGNAL AMPLIFIER 12 7 OSC MIX 6 AUG OUTPUTS INSI89 B RIGHT LEFT CHANNEL DRIVER CHANNEL Driver AND RIGHT AND PHASE INV AND PHASE INV 8 v2 ECC83 12AX7 N 12 7 ECC8 om CHANGER p INT SPKRS RIGHT PUSH PULL LEFT PUSH PULL POWER OUT POWER OUT YS X9 ELL8O RIGHT COM LEFT ELL80 Lum d 6HU8 6HUB 1 8190 FISHER RADIO CORPORATION NEW YORK 95 INT IN U B A 1195 1 PRINTED u20
5. me 435 Composition 33K 10 1W RC30BF333K 2 W n C404 Capacitor Cer Disc 1500 10 508576 4 22 19KC PILOT AND C405 Capacitor Plastic Flim luF 20 m Morbo DUMRSNEFHMK MISCELLANEOUS OES AMPLIFIER cso c Y Plastic Film 033uF 508633 1 1 84 R12DC474J Symbol Description Part No e ECC83 apacitor Plastic Film 033 R405 Reaistor Dep Carbon 470k 5 o ied vin ies 1 84 R12DC474J CR402 Diode V50A260 15 aid E C407 Capacitor Cer Disc 470 pF 10 C50B576 1 R406 Resistor Dep Carbon 470k 575 CR421 Diode 1112 C408 Capacitor Plastic Film 1uF 20 1 8W R120C224J D401 Ring Demodulator V50A260 18 250V C50B633 1 R407 Resistor Dep Carbon 22k 5 L401 Ceil 1 50334 2 C409 Capacitor Cer Disc 820 10 C50B5 76 3 1 8W R12DC223J 1 402 Coil L50334 2 C410 Capacitor Cer Disc 820 10 C50B576 3 R408 Resistor Dep Carbon 22k 5 L421 Coil 20 uH L50334 2 cn Capacitor Plastic Film luF 20 1 8 R12DC223 Z421 Transformer 19 kc 2250210 34 250V C50B633 1 R409 Resistor Dep Carbon 10k 5 2422 Transformer 38 kc 22 50210 54 C412 Capacitor Cer Disc 470 pF 10 C508576 1 1 8W R12DC103J Printed Circuit Bd PB1131B111 C421 Mylar 027 uF 595 100V C50B574 6 R410 Resistor Dep Carbon Im 5 Mini Pin Term A50A577 C422 Polystyrene 180 5 500V 508634 1 1 84 R12DC105J Sleeving 23 32 Lg E50A684 4 sso c o Rr an iru semen
6. STEREOSCAN indicator inoperative Check 15 V402 C406 R433 R434 R435 402 401 Alignment of Z421 1 R401 33K C403 FIGURE 1 Lissajous pattern for MPX Osclilator alignment NO e 2 ON t o8 2 s 4 INPUT INS 281 1 vi wal FIGURE 2 Multiplex alignment coupling network circuit ALIGNMENT INSTRUCTIONS GENERAL The preferred alignment procedure in table 1 below uses a multiplex generator with an RF output like the FISHER Model 300 Optimum performance will be obtained only when the multiplex decoder is connected to the FM detector with which it will be used Check IF alignment first poor alignment can prevent proper multi plex decoder operation TEST EQUIPMENT REQUIRED MULTIPLEX GENERATOR AUDIO AC VTVM 100 KC OSCILLOSCOPE WITH EX TERNAL SWEEP JACKS ALIGNMENT TOOL TABLE 1 ALIGNMENT GENERATOR moving as possible Maximum reading on clean 1000 cps sine wove on oscilloscope TYPE AND CONNECTION Multiplex generator dli R op n 19 epe 17 5 kc VTVM to TP 421 mq Maximum reading on VTVM antenna terminals scope horizontal input 38 ke Lissajous pattern see figure 1 generator not connected should be as slow Composite Same as Step 1 1000 cps on 75 Same as Step 3 unn su right channel only obtained in St
7. not marked uF are pF c6 7 Ceramic 33 N750 1000V 50 70 15 capacitors not marked uF are pF uuF C19 is 5000 80 20 500V 50089 5 8 9 Ceramic 3900 1000V 50072 34 gt 630 QUEM e Symbol Description Part No C10 11 Ceramic 2200 1000V 50072 5 ort No 00 e eni cl Molded 01uF 20 600V 2747 Ci2 13 Ceramic 1800 1000V C50072 8 e Ceramic 21 5 N750 1000Y C50070 32 C21 mea 650190 76 2 Electrolytic 1000 250V C50180 15 C14 15 Ceramic 68 N2200 1000 50070 12 E Hoo O BL 200 380V c3 Electrolytic 4 Section 50180 58 C16 17 Ceramic 02uF 500V C50089 5 100uF 250V 18 19 Ceramic 39 N1500 1000Y 50070 17 _ 4 Ceramic 8 5 NPO 500V 20 08005 0 2105 500V B 40uF 350V C20 21 Mylar 0220 400V 50197 28 E 10 5 150 500V CC20P J100D5 pu 000 480 20K 500V CEP 200uF 350V 22 23 Mylar 022uF 250V 50197 49 c c Room C662 i a 00 1000V D 20uF 350V C24 Molded 01 20 600V 2747 ariable FM 818 116 5 eramic 27 0 0072 1 Ceramic 8 5 NPO 50 1 CC20CJ080D5 C26 Ceramic 5000 80 20 500V 0089 6 10 Ceramic 1000 1000V C50071 2 C27 28 cn Ceramic 33 5 N750 1000V C50070 25 29 Ceramic 330 1000Y 5007241 C12 Ceramic 24 5 N150
8. 0BF151K R14 15 Dep Carbon 1K R33DC102J 43 44 Carbon R33DC102J R15 47K RC20BF473K R16 17 Dep Carbon 100K R33DC104J R45 46 Carbon 6 8K R33DC682J Symbol Description Part No R16 RC20BF 102K R18A R47 48 Composition 100 10 1W RC30BF101K RI 2 100K RC20BP104K R17 47 20 473 19 Pot 500K Dual Boss Treble R50160 138 R49 50 Wirewound 50 iin R556 142 R3 470 208 471 R18 56K RC20BF563K R4 820 RC20BF821K R19 1K RC20BF 102K R5 150K RC20BF154K R20 270 RC20BF271K R67 WK RC20BF102K R21 1 5K RC20BF 152K RB 150 RC20BF151K R22 1K RC20BFTO2K R9 27K RC20BF273K R23 15K RC20BF153K MISCELLANEOUS R10 100K RC20BF104K R24 4 7M 208 475 R1 1K RC20BF102K R25 Dep Carbon 470K 5 1 8W R12DC474J 2 Tene 50187 7 R12 Glass 3 3K 10 7W RPG7W332K R26 27 Dep Carbon 330K 5 1 8W R12DC334J Symbol Description Part No 1 Switch Selector 1078 112 i CRI 2 Diode Silicon Rectifier R50472 2 3 Switch Slide 550200 5 CR3 Diode Silicon Rectifier 1112 Transformer Power T1078 115 n Pilot Bulb 41847 150009 7 T2 Transformer Output 11078 117 2 J Phono Jack 584661 20 1 T3 Transformer Output T1078 117 1 MISCELLANEOUS Symbol Description Part No If replacement janti are out of stock locally they may be obtained Y hae edet 2 directly from the Parts Department of FISHER Radio Corporation 13 Stereo Scan Indica
9. 1000V 50070 8 30 Electrolytic 80 50V C629 138 C13 Ceramic 47 5 N750 1000 C50070 29 C31 32 RESISTORS _ 4 Ceramic 100 5 N1500 1000V 50070 19 33 Ceramic 5000 80 20 500V 50089 6 C15 Ceramic Feedthru 1000 GMV C592 187 C34 Ceramic 560 1000V C50072 14 C16 Ceramic 1000 1000V C50072 3 C35 Ceramic 5000 80 20 500V 50089 4 In ohms 5 tolerance 1 3 W unless otherwise noted Miers R20 Pot 500K Balance Control R50160 137 M Megohms R21A B Pot 500K Dual Volume Control 50160139 Symbol Description Part No R22 23 Carbon 22K R33DC223J RI Composition 820K 10 AW RC208F624K R24 25 Carbon 47K R33DC473J R2 Pot Wirewound 500 Hum Adj R516 128 R26 27 Dep Carbon 390K R33DC394J R3 Composition 1 5K 10 1W RC30BF152K 828 29 Carbon 1K R33DC102J R4 Composition 270K RC20BF274J R30 31 Dep Carbon 220 R33DC221J R5 Composition 470K RC20BF 4745 R32 33 Carbon 47K R33DC474J R6 Composition 1 8K 10 RC20BF 182K R34 35 Composition 150K 10 RC20BF154K RESISTORS AND POTENTIOMETERS R7 Composition 3 3K 10 RC20BF332K R36A Pot 100K Dual AC Balance R1078 116 TM Dap Caron 52306424 E T R13 Gloss 560 10 3W RPG3WS61 R16 11 Carbon 8 2 D J 39 40 Dep Carbon 1M R33DC105J 055 G3W561K 812 13 Composition 18M 10 RC20BF186K R41 42 i Mea R14 150 RC2
10. 12DC103J All circuit with symbols b ginning with C426 Ceramic 02 uF 80 20 500V 50089 4 R421 Dep Carbon 2 2M 5 1 3W R33DC225J 401 are located on the printed circuit board those be C427 Ceramic 2200 20 1000V 50183 10 R422 Dep Carbon 10K 5 1 3W R33DC103J ginning with 421 are mounted on the metal subchassis C428 Ceramic 100 20 1000Y C50183 9 R423 Dep Carbon 1K 5 1 3W R33DC102J CAPACITORS C429 Ceramic 1200 10 1000V C50183 8 R424 Potentiometer 5K Separation n C430 Ceramic 68 10 NPO 1000 C50070 46 Control R50150 11 20 tolerance for oll fixed capacitors unless otherwise C431 Mica 4700 5 300V C50332 7 R425 Dep Carbon 3 9K 5 1 3W R33DC392J noted or marked guaranteed minimum valve C432 Ceramic 5000 20 500V C50089 1 R426 Composition 10M 10 1 2W RC20BF106K C433 Ceramic 39 10 N1500 1000V 50070 17 R427 Dep Carbon 220K 5 1 3W R33DC224J ww All capacitors not marked uF are pF vu R428 Dep Carbon 100K R12DC104J Description No RESISTORS R429 Dep Carbon 1 5M 5 1 3W R33DC155J INDICATOR C401 Capacitor Mylar 047uF 10 100V 50 574 5 Webs Port No e m A Wm pere AMPLIFIER C402 Capacitor Polystyrene 2700 5 R401 Resistor Dep Carbon 33k 5 R432 Dep Carbon 150 5 1 3W 2 R33DC151J 125 508634 20 1 8W R12pC333J R433 434 j 403 Film luF cionis R402 li onu Dep Carbon 1 5 5
11. MPX input with a 180 pF citor from the MPX input end of the resistor to ground Figure 2 on schematic TEST EQUIPMENT REQUIRED MULTIPLEX GENERATOR AUDIO AC VTVM 100 KC OSCILLOSCOPE WITH EX TERNAL SWEEP JACKS ALIGNMENT TOOL TABLE 2 GENERATOR Composite output of PX generator to input of MPX demodulator Point 1 19 ke output of generator to oscillo scope horizontal input generator not connected to MPX section 19 ke pilot only 100 mV RMS 280 MV P P to 421 Set frequency of free running oscillator as close as possible to 38 kc Lissajous pattern see figure 1 should be slow moving as possible Oscilloscopes vertical input to TP 422 VTVM and oscilloscope vartical input to left channel output lug 1000 cps on watt channel dae Maximum reading on VIVM clean 1000 cps sine wave on oscilloscope Same VTVM reading as obtained in Step 3 2 db clean 1000 cps sine wave on oscilloscope Minimum reading on VTVM should be at least 33 db below reading obtained in Step 5 7 V RNS 7 V RMS VTVM and oscilloscope Same as Step 1 Same as Step 4 3 VP terminal 15 7 V RMS 0 3 92 V P P terminal IR Minimum reading on VIVM should be Same as Step 1 1000 cps on 9 Same os Step 3 MPX separation at least 33 db below readin EM right channel only 3 92 V control
12. NTINUOUS IMPROVEMENT FISHER RADIO CORPORATION RESERVES THE RIGHT TO MODIFY ANY DESIGN OR SPECIFICATION WITHOUT NOTICE AND WITHOUT INCURRING ANY OBLIGATION am a o who cy o 4 o c m ALIGNMENT INSTRUCTIONS Read these instructions very carefully before attempting alignment Adjust line voltage power input to chassis for 117 volts AC 50 to 60 cycles Use only the proper fully insulated alignment tools 1t the low frequency end of the dial scale Reset the Reduce signal generator output during alignment to keep dial pointer if necessary VTVM reading below that specified for step 1 Narm up the chassis and the test equipment for at least Repeat steps 4 and 5 to obtain proper dial calibration 15 minutes and maximum sensitivity DIAL SIGNAL GENERATOR DC VTVM ADJUST INDICATION GENERATOR FREQ Ungrounded tube Set the SELECTOR switch to the MONO position Set tuning dial to the extreme low frequency position Dial pointer should line up with the calibration mark TIL 73 T4 and T5 top and bottom Maximum negative voltage below 20 volts Test Point 3 Set dial shield of V2 pointer for extreme Hot leud of DC VTVM low frequency to TEST POINT 4 position Ground lead of DC VTVM to junction of Zero indication on two serles connected external resistors 47K 5 wired be tween TEST POINT 3 and ground
13. RA obtained In Step 3 9 0 vertical input to right channel output lug 5 Step 1 ll cene off 9 Some as Step 5 Step channel only me as Step contro 3 92 V P P if necessary f adjustment is required adjust for best compromise readings in Steps 4 and 6 vn R 100K TUNER SCHEMATIC p c3 11000 81 SELECTOR SWITCH OFF SHOWN IN R3 470 NOTES 1 FOR ALL VOLTAGE AND CURRENT MEASUREMENT SET LINE VOLTAGE TO 2 DC VOLTAGE MEASURED WITH DC VTVM TO CHASSIS WITH NO SIGNAL INPUT SELECTOR SWITCH IN FM POSITION FERRI C35 1000 3 n 3 TN i 3 x h 32 c3 8000 du 5000 vg 000 E t TEST POINT vi4 U EM vi MOM m GAUG 6 56 EF94 ANDE an eek 25 i c 25 inr 160 2700 TESTPOINT 146v C21A 6218 40U 20UF INOICATOR 3 PII94 AW2387 TUNER PARTS DESCRIPTION LIST AMPLIFIER PARTS DESCRIPTION LIST CAPACITORS CAPACITORS 10 tolerance for al fixed capacitors unless otherwise C4 Electrolytic 8uF 50V C629 138 10 tolerance for all fixed capacitors unless otherwise i noted or marked GMY ii minimum value All c5 Mylar 047uF 250V 50197 52 noted or marked guaranteed minimum value All ish 2700 iov aM 7 capacitors
14. a replacement power transistor be sure the bottom of the flange the mica insulator and the surface of the heat sink are free of foreign matter Dust and grit can prevent perfect contact This re duces heat transfer to the heat sink Metallic particles can puncture the insulator and cause shorts ruining the transistor e Silicone grease must be used between the transist or and the mica insulator and between the mica and the heat sink for best heat conduction Heat is the greatest enemy of electronic equipment It can shorten the life of transistors capacitors and resistors Use Dow Corning DC 3 or C20194 or equivalent compounds made for power transistor heat conduction e Use care when making connections to speakers and output terminals Any trayed wire ends can cause shorts that may burn out the output transistors they are direct coupled to the speakers There is no output transformer nothing to limit current through the tran sistors except the fuses To reduce the possibility of shorts at the speakers lugs should be used on the exposed ends at least the ends of the stranded wires should be tinned to prevent frayed wire ends The current in the speakers and output circuitry is quite high Any poor contact or small size wire can cause power losses in the speaker system Use 14 16 AWG for long runs of speaker connecting wiring DC Voltage Measurements These basic tests of the transistor circuitry are made withou
15. ep 3 VTVM and oscilloscope Same readi ob ng as obtained Same Step 1 Same as Step 4 75 kc neut ie tan Step 3 2 db clean 1000 cps sine terminal 15 wave on oscilloscope 19 ke output of Set frequency of free running Vertical input of oscillo scope to 422 set oscillo scope for external sweep to MPX section Minimum readin on VTVM should be Composite MPX MPX separation Minimum eatin on VTVM should Same as Step 1 1000 cps on 75 kc b left channel only Same as Step 5 control R4 be at least 33 db below reading f adjustment is required adjust for best compromise readings in Steps 4 and 6 a generator to oscillo oscillator as close as possible to VTVM and oscilloscope we oon 475 ke vertical input to right channel output lu left channel only terminal g at least 33 db below reading if necessary obtained in Step 5 1131 2 MULTIPLEX PRINTED CIRCUIT f ds IS e 6405 276 R407 22K m IL IIK iJ INS256 MULTIPLEX SECTION ALTERNATE ALIGNMENT PROCEDURE For multiplex generators without an RF output When using this alignment procedure it is necessary to disconnect the ratio detector from the multiplex decoder at the point where the generator is connected Unsolder point 1T carefully The generator input must be through a simple low pass filter a 12 resistor between the multiplex generator and the
16. er DC voltages at CR2 C2 R3 R3 R6 C3B R6 R7 R7 C3D Hum in any position of the SELECTOR switch Check Setting of HUM ADJUST CONTROL R2 295 volt DC power supply filter C3A B C D 9 Bias supply ond C4 for AC ripple Distortion Hum Weak or No audio output Hum or No audio output LEFT channel only SELECTOR PHONO FM positions Remove plug from LEFT RCRDR OUT jack if used Test filament leakage for hum or substitute V1 V4 V5 RIGHT channel only SELECTOR in PHONO and FM positions Remove plug from RIGHT RCRDR OUT jack if used Test filament leakage for hum or substitute V1 V4 V5 Hum or No audio output SELECTOR in PHONO positions only Check J3 J7 J9 and their plugs and interconnecting cables to the record player Cleon and tighten all ground connections Reverse line cord plug in wall outlet Reverse line cord plug from record player in 18 on chassis if used SELECTOR in FM position only Hum or No audio output Try other stations 9 Reverse AC linescord plug in wall outlet Check Antenna connections and antenna outdoor Test filament leakage for hum or substitute V11 12 V13 V14 Hum SELECTOR in FM STEREO position only No audio output Distortion Check Balanced modulator D401 and C409 C410 C407 C412 1 401 L402 Test filament leakage for hum or substitute V401 V402
17. itable when testing an individual stereo channel When a good tube is switched with a defective one of the same type the symptom will be transferred from one stereo channel to the other When substituting tubes it is absolutely necessory to be certain the tube being inserted is good a new tube from a freshly opened carton is not necessarily a perfect tube De fects con occur from shipping ond hondling If you have any doubts about the quality of a tube try it in an identical circuit that is operating properly For example a tube with heater cathode leakage may operate normally in a circuit with its cathode grounded transpose switch it with one in a circuit that has a cathode bias resistor and it will cause a lot of hum Does not go on pilot or dial lamps do not light in any position of the SELECTOR switch Check AC interlock plug and socket power cord and plug wall outlet Automatic shut off switch S1 pert of SELECTOR switch Power switch S4 Does not go pilot or dial lamps do not light only in PHONO positions of the SELECTOR switch Check Automotic shut off switch 51 part of SELECTOR switch J9 and its plug and the interconnecting cable and the turntable switch on the record player Distortion Hum Weak or No audio output Check Both channels any position of the SELECTOR switch SPKR switch position and its operation Test or substitute V1 Test for prop
18. ny work on the transistor amplifiers without first disconnecting the AC power linecord wait until the power supply filter capacitors have discharged e Guard against shorts it takes only an instant for a base to collector short to destroy that transistor and possibly others direct coupled to it In the time it takes for a dropped machine screw washer or even the screwdriver to glance off a pair of socket terminals or between a terminal and the chassis a transistor can be r ined e DO NOT bias the base of any transistor to or near the same voltage applied to its collector e DO NOT use an ohmmeter for testing transistors The voltage applied through the test probes may be higher the base emitter breakdown voltage of the ransistor Output Stage and Driver Replacements for output and driver transistors if necessary must be made from the same beta group as the original type The beta group is indicated by a colored dot on the mounting lange of the transistor Be sure to include this in formation when ordering replacement transistors e If one output transistor burns out open or shorts always remove all output transistors in that channel and check the bias adjustment the control and other parts in the network with an ohmmeter before insert ing a new transistor All output transistors in channel will be destroyed if the base biasing circuit is open on the emitter end e When mounting
19. op to keep the spring stretched while stringing the dial cord Place the piece of stiff wire in the outer groove of the driveedrum bridging the slot in the drive drum Tie a small non slip loop in the end of the dial cord Thread the loop in the dial cord through the opening in the drive drum slot under the spring and hook the loop over the top ear inside the drive drum Wrap the dial cord around the drive drum counterclock wise about of a turn in the inner groove and then around the top guide pulley 9 Stretch the dial cord to the left end of the dial around the two guide pulleys ond then back to the fly wheel drive shaft Wind 3 full turns of dial cord around the drive shaft as shown in the upper detail drawing While keeping the dial cord taut rotate the drive drum to 3 FULL TURNS INNER GROOVE OUTER GROOVE TO INNER GROOVE ins 308 TO OUTER GROOVE its extreme clockwise position and fit the dial cord into the remaining pulley Set the dial cord in the outer groove of the front end drive drum and thread it through the loop in the end of the tension spring See detail drawing at lower right Pull all slack dial cord through the loop in the tension spring Check all pulleys for proper threading of the dial cord Tie o small knot the dic cord to secure it to the loop in the tension spring Use a tweezer with a small tip to help tie the knot Keep dial cord as tau
20. ring A well tinned hot clean soldering iron tip will make it easier to solder without damage to the printed circuit board or the many many circuit com ponents mounted on it It is not the wattage of the iron that counts it is the heat available at the tip Low wattage soldering irons will often take too long to heat a connection pigtail leads will get too hot and damage the part Too much heat applied too long will damage the printed circuit board Some 50 watt irons reach temperatures of 1 000 F others will hardly melt solder Small diameter tips should be used for single solder connections larger pyramid and chisel tips are needed for larger areas e When removing defective resistors capacitors etc the leads should be cut as close to the body of the circuit component as possible If the part is not being returned for in warranty factory replacement it may be cut in half with diagonal cutting pliers to make removal easier e Special de soldering tiplets are made for unsolder ing multiple terminal units like IF transformers and electrolytic capacitors By unsoldering all terminals at the same time the part can be removed with little chance of breaking the printed circuit board e Always disconnect the chassis from the power line when soldering Turning the power switch OFF is not enough Power line leakage paths through the heating element can destroy transistors Transistors Never attempt to do a
21. t os possible while tying the knot Apply a drop of quick drying cement to the knot to prevent it from slipping or becoming undone After the cement has dried completely pull out the piece of stiff wire and gently let the spring contract to apply tension to the dial cord a Rotate the front end drive drum to its extreme counters clockwise position Set the dial pointer to zero 0 calibration on the loge ging scale of the slide rule dial Attach the pointer to the dial cord and cement it in place with a drop or two of quick drying cement If replacement parts are out of stock locally they may be obtained directly from the Parts Department of FISHER Radio Corporation They will be shipped best way either prepaid or C O D unless i otherwise specified For instrument operation information and technical assistance write Richard Hamilton Customer Service Department FISHER Radio Corporation Long Island City New York 11101 TROUBLESHOOTING GUIDE When a defect occurs on electronic circuit the first component suspected is usually the vacuum tube Mony of the inexpensive tube testers will not indicate all the possible internal faults vacuum tube slight defects often sneak past these testers t is better to substitute another tube of the same type Sometimes it is possible to switch transpose tubes from one circuit to another This method of testing is most su
22. t the signal gener ator Without any signal input measure the circuit volt ages as indicated on the schematic The voltage difference between the base and the emitter should be in the millivolt range a sensitive DC meter is needed for these readings low voltage range of 1 volt full scale or lower is needed Audio Voltage gain Measurements The schematic and printed circuit board layout diagrams are used Input signals are injected at the proper points found most quickly by using layout of the printed circuit board instead of the schematic An AUDIO AC VIVM connected to the test points should indicate voltages close to those values shown in the boxes on the sche matic Many of the signal levels in the input stages are only a few millivolts they can not be read on the AC ranges supplied on most Vacuum Tube AC DC Volt ohmmeters VTVMs Even with a 1 volt range a signal level of 100 millivolts 1 volt will be the first 1 10 of the mater scale A reading of 1 millivolt 001 volt wil hardly even move the meter needle Hook one end of the spring over the bottom ear in the front end drive drum with the drum rotated to its extreme counterclockwise position Stretch the tension spring until the loop on the free end sticks out of the slot in the edge of the drive drum Now insert a length of stiff wire about I inch long a piece of straightened out paper clip will do nicely through the lo
23. tor 150B621 2 L8 Choke 3 3 Microhenry 1 50066 8 They will be shipped best either prepaid C 0 D unless e 00 otherwise specified L3 Choke RF 629 180 22 Transformer FM IF 112987 i L4 Coil FM RF L8 14 2 oil Limiter For instrument operation information and technical assistance write L5 Coil FM Oscillator 5818 118 74 Transformer Ratio Detector Z250210 9 Richard Hamilton Customer Service Department FISHER Radio Corporation Long Island City New York 11101 1131 2 MULTIPLEX schematic 1N R402 6402 poem 000 PITE NO 1 175 75V 22K IOK C407 P C424 R430 2422 470 lr PBIISICIIS l 220 47K on J 3 H 820 1 R40 pone 40 LEFT OUTPUT v40 V402 i 20mH RIGHT OUTPUT TO STEREO SCAN INDICATOR T T P 421 R428 C426 190 TO ALIGN METER SWITCH NOT USED ON ALL MODELS C427 C429 2200 CR421 1200 PBIISICIIS R42 390K VOLTAGES CAN VARY 220 STEREO MONO 22550 120 PII3I SCHEMATIC T Symbol Description Port No Symbol Description Part No PARTS DESCRIPTION LIST C423 Polystyrene 4700 5 125V C50B634 21 RAM Resistor Dep Carbon Im 5 1 8W R12DC105J C424 Polystyrene 220 5 500V C50B634 2 R412 Resistor Dep Carbon 10k 5 i 425 Polystyrene 4700 5 125V C508634 21 ew R
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