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AL-80B

1. amp Export Modifications adieu ene a a 9 Technical Assistance is and see l 9 Installation Guidelines And Suggestions a B a didt ad 10 Location Of The Amplifier ta a da eet 10 Ventilation A a EE 10 Power ti u sata ch bti ege Pd e E dwan ia l a Sa 10 is Ai LA A gia 11 Transformer COBDOCHODS i e Be 12 Interconnect OHSA fta us izda 13 Operating Instructions And 13 Front Panel Controls metin ote petu de D sat Uu Ea eet du de ddl aaah aa 13 MULTIMETER 5 tur get 13 ONS cee angele 13 SIBX OPR Switch il gi A EH E Up 14 PEATE a TM AN 14 EOAD Controls a aa ta a 14 ALC Metering Controls and Adjustments eon 14 ALC Metering PUnCtons essor eri tty XU NV 14 CONOIS BA ur dieto upset s Miu 15 z u cay oor en e dl 15 Rear panel ALC LIMIT control ii i 16 ALE Limit Adjustment rear panel ied cited rat ad eo area ebda 17 Dayne PO WE Susu beo tnc NI uta 17 E bi rino RT NOR 18 Tuning Proced Ure RT EC ae ane oath uta chal neces acs ate catia 18 iii AL 80B Instruction Manual Additional SSB Notes ape WR E S
2. mains Contact with the voltages in this amplifier can be fatal The tube must be installed in its socket prior to operation Observe the pin configuration on the tube and the socket One of the pins is separated by a large space from the other four pins Carefully observe the pin alignment to be sure the tube pins are centered on the socket s holes Firmly press the tube into the socket Do NOT twist or force the tube into the socket Install the anode connector on the tube s anode terminal and secure it with the screw provided Snug the screw enough to secure the anode connector Do not over tighten the screw Install the fuses and fuse caps on the back of the amplifier This amplifier uses two 20A fuses for standard 120 Vac operation models B and BY or two 10A fuses for 240 Vac operation model BX only If you wish to operate the amplifier on a line voltage other than 120 Vac the jumpers on the power transformer primary windings must be changed If the primary wiring is changed the correct fuses must be installed See the Transformer Connections section on page 12 for more information CAUTION Always use fast blow fuses rated at 250 Vac or higher NEVER use standard automotive glass fuses or slow blow fuses The top cover should now be installed with the side ventilation holes positioned on the left front vlew The ventilation holes on the top of the cover should be on the right side of the amplifier front view Secure the cove
3. Water pipes metal heating ducts metal fences and other large metallic masses offer convenient RF grounds If a water pipe ground is used inspect all the pipe connections to be sure that no plastic or rubber connections are insulating the pipes Insulated pipe connections will interrupt the electrical continuity in the water supply system Install a jumper around any insulated pipe connections you find Use heavy copper wire or flashing with stainless hose or pipe clamps for the jumpers The following tips will help prevent lightning damage and RF grounding problems 1 Avoid using braided or woven conductors they have very high resistance for RF and lightning Remember that RF and lightning flows along the surface of conductors almost no current flows in the center of the conductor The lowest RF resistance occurs with wide smooth conductors 2 Avoid routing a single small gauge conductor along the various pieces of equipment or to connect multiple ground sources Instead use multiple ground leads that connect to a single wide buss at the operating position Keep all ground leads as short and wide as possible 3 Buried radials provide much better lightning and RF ground connections than ground rods do although both are needed for safety 4 Avoid sharp bends in ground leads When changing the direction of a ground lead use a gradual radius turn 5 Avoid second story operation A good ground is much easier to obtain on the first floo
4. and high voltage Current meter Plate and grid current simultaneously on separate scales ALC Negative going 0 to 10 volts adjustable Relay Requires contact closure or sink of 12 Vdc at 100 mA Back pulse protected Connectors RF SO 239 Line NEMA 5 15P standard 120 V three wire Others RCA Phono Physical Dimensions 15 1 2 D x 14 1 2 W x 8 1 2 H Weight 48 lbs AL 80B Instruction Manual Introduction The Ameritron AL 80B is an 800 watt CW 1000 watt PEP output linear amplifier that operates on all Amateur bands from 160 through 15 meters The AL 80BX and AL 80BY are export models that operate from 160 through 10 meters Export modification instructions are available with proof of a valid amateur radio license The AL 80B uses a single 3 500Z tube in a class AB2 grounded grid circuit High quality power supply and RF components combine with an accurate peak detecting directional coupler front panel adjustable true ALC circuit and automatic bias switching to make this the best featured and most reliable single 3 500Z amplifier available The AL 80B and AL 80BY are factory wired for 120 Vac 50 60 Hz line voltage The AL 80BX is factory wired for 240 Vac All models are easily converted to other supply voltages between 90 and 250 Vac Safety Interlock The top cover of the AL 80B operates an interlock switch which completes the primary circuit of the power transformer The interlock will open and de energize th
5. flat topping and producing excessive distortion products A second method of determining linear operation is to monitor the peak RF output power carefully on the AL 80B s internal meter Determine the maximum obtainable RF output power and reduce the exciters power until there is a noticeable margin from the maximum output power This will insure some reserve power is available for random voice peaks NOTE Never increase the drive power beyond the point where the amplifier s output power stops increasing This is also the point where the grid current will begin rising rapidly The amplifier is being over driven for a given LOAD setting when the grid current increases rapidly while the plate current and output power increase slowly The amplifier LOAD control needs to be advanced to a higher number if this condition occurs Non linear operation splatter and excessive grid current will occur if the LOAD setting is too low Excessive plate current is the proper indicator that the drive power limit has been reached 17 AL 80B Instruction Manual Tube and Component Life These guidelines will help prolong tube and component life and minimize splatter 1 On SSB or other linear modes virtually any amount of power will cause splatter if the loading is too light LOAD control too far counter clockwise Always tune for maximum output with maximum drive power Reduce the drive power to reduce the output power on SSB not the loading con
6. will produce the best audio quality The drive can be increased for DX or weak signal SSB operation until the ALC steadily registers voltage Also see the ALC Adjustment section on page and the Multimeter section on page f 21 AL 80B Instruction Manual Additional SSB Notes The peak power output developed on SSB is limited bv the amplifier loading RF drive and peak to average power of the RF waveform Proper loading of this amplifier will produce excellent linearitv and a clean signal even if the output power level exceeds one kilowatt PEP An improperlv adjusted too far counter clockwise LOAD adjustment can produce flat topping and splatter with only a few hundred watts of RF output The LOAD setting is the single most important adjustment for proper SSB operation Note The LOAD control setting is the most important adjustment for good linearity To maintain linearity always be sure that the LOAD control is adjusted far enough clockwise for the peak drive that will be applied Be considerate of others NEVER push this amplifier into envelope clipping or to the point where the grid current approaches 75 mA on voice peaks Envelope clipping can be also be avoided by adjusting the amplifier s ALC SET control until the peak output power drops slightly from the power obtained with full microphone gain and a fully clockwise ALC SET adjustment For the cleanest audio the microphone gain can be reduced until the ALC
7. 100 watts of short term average envelope power NEVER allow the grid current to exceed 250 mA under any operating condition Maximum power output normally will occur with approximately 175 mA of grid current on CW or approximately 45 mA of maximum grid current 175 mA instantaneous peak on SSB two tone test The grid dissipation with 175 mA of grid current and 70 watts of drive is approximately ten watts If you wish to add control grid protection to the AL 80B always remember fuses and resistors are too slow and unpredictable to adequately protect tubes While grid protection is generally not required with tubes like the 3 500Z Ameritron does offer an optional fast acting electronic circuit that will rapidly disable the amplifier if excessive grid dissipation occurs This circuit also reduces or eliminates the chance of tank component damage from incorrect loading or a load failure The part number of this add on board is 50 01172 1 AL 80B Instruction Manual The continuous commercial plate current rating of the 3 500Z is 400 mA For maximum tube life plate current should be maintained below 400 mA on CW and other steady carrier modes Brief periods of plate current exceeding 400 mA will not cause loss of emission or shorten the life of the tube in this amplifier The application of filament voltage causes thermal stresses from rapid and uneven temperature changes Needless cycling of the filament may cause premature failure or unnece
8. Ameritron PN D301 C301 302 C303 304 307 311 314 315 C305 306 R301 302 R303 R304 R305 R306 310 R307 R308 311 R309 R312 R313 IC301 IN34A 47 uF 50 V tantalum uF 50V 001 uF 1 kV 2 2M 1 4 W 390 ohm 1 4 W 2 2k 1 4 W 470k 1 4 W 10k 1 4 W 100 ohm 1 4 W 33k 1 4 W 4 7k 1 4 W 330 ohm 1 4 W 270 ohm 1 4 W 300 0346 203 0530 200 0754 200 2120 100 6220 100 0390 100 1500 100 0188 100 4100 100 2100 100 3330 100 1470 100 0330 100 0600 311 0324 Q301 302 305 0645 Q303 305 0722 5301 2 6 500 0563 26 AL 80B Instruction Manual Timer Overload Board 50 0080 5 C501 506 200 0416 C507 508 203 0530 C509 203 0564 D501 502 300 0266 D503 301 710 IC501 311 0724 Q501 305 3055 Q502 307 0722 Q503 504 305 0645 R501 503 101 0643 R504 505 100 0729 R506 508 100 0532 R507 100 0728 R509 100 0730 R510 100 0727 R511 101 0384 RLY501 408 2135 FB 73 801 Ferrite Bead 10 15168 w 27 AL 80B Instruction Manual Al 80B Main Chassis Parts List 410 3138 001 uF 7 5 kV 200 7224 a 500 pF Doorknob 7 5 kV 210 0470 C5 6 209 0559 2042112 204 2573 1 320 0522 1 2 See Jumper Connections Chart page 50 0080 1 50 0080 1 50 0080 2 50 0080 2 50 0080 3 50 0080 3 R a 50 0080 4 50 0080 4 50 0080 5 50 0080 5 10 13165 10 13240 10 13108 400 3581 400 3580 105 1301 105 1341 Parasitic choke 10 15105 Plate Choke 10 15197 402 1162 Band Switch 500 2135 Lighted Sw
9. for various supply voltages This amplifier has a current demand of 14 amperes at 120 Vac with 1000 watts of RF carrier output The average power line current during voice peaks on SSB will be approximately 9 amperes at 1000 watts PEP output The average current demand on CW will be less than 12 amperes Most normal residential power lines and house wiring will easily meet this current requirement 10 AL 80B Instruction Manual If the power mains have excessive resistance the high voltage mav sag to less than 2700 volts under load Voltage sag will not hurt the amplifier if the fullv loaded high voltage remains above 2500 volts CAUTION Never allow the high voltage to exceed 3200 volts under any condition For 120 Vac operation the wiring between the fuse box and the amplifier ac outlet must be number 14 gauge or larger in order to supply the current required 12 A without a significant drop in the line voltage The 120 volt outlet should be fused for 20 amperes Grounding Connect a good RF and dc ground to the ground post on the rear panel of the amplifier Use the heaviest and shortest connection possible The best materials to use for ground connections are in order of effectiveness smooth wide copper flashing copper tubing or solid copper wire Never use braided or woven conductors unless the lead needs to be flexed Braided or woven conductors offer a much higher impedance to lightning and RF than equivalent solid conductors
10. have installed the optional electronic grid protection circuit to prevent control grid damage this amplifier will quit operating if the grid dissipation exceeds a safe pre set limit The overload circuit responds much faster that the grid current meter The overload circuit can respond to excessive grid current before the operator is able to observe excessive current on the grid meter Some exciters generate brief high level RF pulses when first keyed These short duration pulses may greatly exceed the exciter s operating output power setting but may not be indicated on meters Unexplained activation of the grid overload circuit may indicate the existence of this exciter problem The grid overload circuit can be reset by momentarily placing the STBY OPR switch in the STBY position 18 AL 80B Instruction Manual Never under load the amplifier to reduce the output power The amplifier LOAD control must be set to a high enough position clockwise to prevent excessive voltage and arcing in the tank circuit or excessive grid current Repeated tripping of the grid overload circuit or intermittent arcing probably indicates the LOAD control is adjusted too low 1 Set the AL 80B front panel switches as follows POWER to OFF OPR STBY to STBY MULTIMETER to HV 2 Plug the ac line into the proper voltage outlet 3 Place the main power switch in the position The meter lamps should light and the blower should start Read the 350
11. pila E fi 9212 dec 8EI2 4 1 6112 alla sta ZS ZS 8113 9112 ezia peta 6114 ar 2 SSS 1nO 38 i Tats coto 1 SZ 210 5219 9019 S I rat caro 1 NI 34 ANBL LAdNI gt C 1 9 60 52010 Oo 206 Cees C2108 Cate AMER I TRON 116 WILLOW ROAD PERRY STARKVILLE MS 39759 R311 E R303 10 0381 9 5 Ki 0303 C303 ALC ADI 25 M R305 R384 R313 nuc l i 12V TO STBY SW R318 R389 314 ODEL NO ALBBB 5 0080 3_ 3 3 DESCRIPTION METER BOARD DATE AMERITRON REVISED AN BV 116 WILLOW ROAD C PERRY STARKVILLE MS 39759
12. very close to the plate current dip LOAD Control This control adjusts the coupling of the amplifier to the antenna or load This adjustment insures optimum coupling between the tube and the load as the SWR of the load the operating frequency or the power level is changed Advancing the LOAD control clockwise increases the RF power output capability and the linearity of the amplifier Advancing the LOAD control also decreases the grid current and increases the plate current for a given amount of drive The efficiency of the amplifier and the grid current decrease if the LOAD control is rotated beyond the point of maximum output The linearity however will increase The proper position for this control is slightly clockwise from the setting that produces maximum output with full drive power applied to the input Never use this control to adjust the output power The PLATE control should always be checked after the LOAD control is adjusted by more than one number This is especially important at the high end of the LOAD range on 20 meters and above For example if the LOAD is advanced from 7 1 2 to 8 3 4 the PLATE should be re tuned If the LOAD is touched up only a slight amount the PLATE setting will not usually require re adjustment ALC Metering Controls and Adjustments ALC Metering Functions The MULTIMETER switch in the AL 80B has two positions that indicate the functioning of the ALC circuit These posit
13. voltage heavy duty transformer with a unique buck boost winding allows adjustment of the primary voltage to 14 different voltages centered on 115 and 230 Vac This versatile Ameritron feature allows the user to select the optimum primary voltage for maximum performance and life 9 The tuning and loading controls have vernier 6 1 reduction drives for smooth tuning Logging scales allow quick and repeatable control adjustments for rapid band changes 9 The AL 80B has two illuminated cross needle panel meters The left meter provides a continuous reading of grid and plate currents The right meter indicates peak RF power output on one scale and Plate Voltage HV Reflected power and SWR REF ALC detector voltage ALC and ALC adjustment level ALC SET on the other 9 Filament and plate voltages are maintained using the STBY OPR switch This allows the amplifier to be conveniently bypassed for barefoot operation 9 front panel ALC SET control allows convenient adjustment of the ALC threshold The unique ALC circuit samples the grid current and power supply voltage An XMT LED on the front panel indicates proper keying of the amplifier by the exciter rear panel 12 V auxiliary output jack provides up to 200 mA at 12 Vdc for accessories such as the ATR 15 Antenna Tuner 9 A step start circuit limits the inrush current to the power supply and tube filament This circuit extends the life of the amplifier components AL 80B
14. 0 volt scale on the multimeter It should indicate 3100 volts nominal and no more than 3200 volts 4 With the amplifier still on STBX tune the exciter into a normal 50 ohm load according to the manufacturer s instructions solid state radios do not normallv require this adjustment Turn the exciter drive down after tuning 5 Place the amplifier s BAND switch on the same band as the exciter Set the PLATE control and the LOAD control as indicated below CW pl l5 quo o aoo 9 pj 7 PHONE SSB 231350 TT 2850 9 4 8 19 AL 80B Instruction Manual 6 With the exciter s drive level still on zero observe the 750 mA 1 scale on the left hand meter It should indicate zero 0 amperes 7 Place the STBY OPR switch in the OPR position Place the exciter in the transmit mode with no RF output The red XMT LED should light and the plate current Ip on the left meter should be close to zero 0 8 With the exciter in the transmit mode applv a verv low amount of RF drive power about 100 mW The plate current Ip should suddenly increase to nearly 100 mA Currents may vary up to 25 due to component and line voltage tolerances If the current in this step is higher than expected the RF level from the exciter may be too high If the exciter does not allow adjustment to very low CW power levels the exciter can be placed in the SSB mode and the audio microphone gain control advanc
15. AL 80B Instruction Manual WARNING I NEVER APPLY POWER TO THIS AMPLIFIER WITH THE COVER REMOVED CONTACT WITH THE VOLTAGES INSIDE THIS AMPLIFIER CAN BE FATALI PLEASE READ THIS MANUAL BEFORE ATTEMPTING TO OPERATE EQUIPMENT Improper or abusive operation of this amplifier can damage the tubes or other components in this amplifier Damage caused by improper or abusive operation is not covered under the warranty policy AL 80B Instruction Manual Unpacking Instructions Remove the 3 500Z tube from its shipping carton Carefully inspect the tube for visible damage Look for bent or broken pins Roll the tube over slowly while listening and watching for loose internal materials Be sure the anode is not off center at the end away from the anode connector Contact either your Ameritron dealer or Ameritron immediately if any damage exists Carefully lift the amplifier from the shipping carton and place it on a firm level surface Inspect the amplifier for shipping damage Contact either your Ameritron dealer or Ameritron immediately if any damage exists Remove the cover screws with a 2 Phillips screwdriver Save the screws to re secure the cover Carefully lift the rear of the cover while sliding the cover back The AL 80B is shipped with the fuses and fuse caps packed inside the amplifier Additional screws will be included in the fuse pack if they are required WARNING Never remove the cover while this amplifier is connected to the power
16. Instruction Manual AL 80B Technical Specifications Input Circuit tvpe Maximum VSWR at resonance Minimum 2 1 VSWR bandwidth Maximum drive power permissible Tvpical drive for full power output Output Circuit tvpe Tvpical SSB PEP voice operation CW continuous operation 1 2 hour two tone test 1 2 hour continuous carrier RTTY Frequency Coverage Third Order IMD Efficiency CW SSB Power Supply Circuit type No load voltage Full load voltage Full load current Regulation Transformer Capacitors Normal line current at rated CW output Normal line current at 1000 watt PEP output Power line current in standby Tube Type Continuous dissipation Warm up time Estimated life Pi network slug tuned coils 1 3 1 or less 20 of center frequency 100 watts PEP 85 watts Pi L Pi network 1000 watts 800 watts 850 watts 500 watts 1 8 to 21 MHz amateur bands Export models include 24 5 and 28 MHz 35 dB or better at rated output approximately 65 approximately 65 envelope crest Full wave voltage doubler 3100 V 2700 V 6A gt 13 26 Ib E I lamination grain oriented 26 mFd total computer grade 12 A at 120 Vac 8 A at 120 Vac 1 A at 120 Vac 3 500Z 500 watts 10 seconds 12 000 hours ICAS Metering Multimeter Peak forward power continuous The second scale switches between peak reflected power and SWR ALC threshold ALC output voltage
17. a I IA p ae 22 AM Amplitude Modulation Operation a 22 FM Frequency Modulation RTTY and Digital Operation 22 Audio BIL editi M aa 22 E ada aysa 23 Periodic Maintenance PUn eren ER aa Skedata 23 Parts LISt u una A 23 Power Supply SWR Board 50 0080 0 25 Tuned Input Board 50 0080 2 Sane odia Ee ette a 26 AL SOB D uned Input att ido n ede ode tdeo edel pedi isi 26 Meter Board 650 0080 3 phai ks tecti vot isi pieta 26 Timer Overload Board 50 0080 5 27 Al 80B Main Chassis Parts Ist ss i ib ie Go Gi ODIUM DRM led hn 28 Frequency COVELdBO Es biet la e in t ut q a 29 Amplifier Log M 29 Notes a sap 30 iv AL 80B Instruction Manual Features 9 The AL 80B uses a rugged inexpensive 3 500Z tube 9 The 3 500Z requires only a few seconds of warm up time 9 dynamic bias circuit eliminates hundreds of watts of unnecessary heat generation in the power amplifier tube The result is cooler operation and longer component life 9 multi
18. apacitors Placing an air filter over these air inlet holes will substantially reduce the amount of dust entering the cabinet Most hardware stores stock suitable air filter material that are used as replacement filters for window air conditioners 24 AL 80B Instruction Manual Parts List Power Supplv SWR Board 50 0080 1 D101 102 114 115 300 0346 D103 305 0757 D116 120 300 0266 D104 113 300 0145 C101 208 5404 102 105 200 2120 103 200 3531 C104 204 0150 C106 125 126 129 135 137 200 0416 C140 203 0530 C107 116 200 2121 C117 124 203 0578 C127 208 5775 C128 138 132 139 200 0754 C130 131 200 2122 C133 203 0207 C134 203 0565 R101 103 1747 R102 100 0188 R103 104 121 100 4100 R105 100 0727 R106 103 3400 R107 103 3399 R108 109 103 2223 R110 111 103 1743 R112 119 103 7580 R120 103 2151 R122 103 1747 R123 100 0728 R124 125 104 0400 R126 128 128 101 0402 R127 103 9702 R130 101 1470 RLY101 408 6140 RLY 102 408 6148 RFCIOI 10 15168 T101 10 14134 Q101 305 0645 Q102 305 0722 Q3 see main chassis 305 3055 F101 755 1102 A 25 AL 80B Instruction Manual Tuned Input Board 50 0080 2 C201 tube side L201 5201 C202 transmitter side P AL 80B Tuned Input Chart BAND C201 pF tube L201 C 201 pF transmitter side 700 208 5689 28 75 405 1287 2000 208 5608 80 i300 208 5177 23757 405 227 00 0208 5176 220 208 5175 Meter Board 50 0080 3 Designator Description
19. at uses a negative going ALC voltage of up to 10 volts Note Transceiver ALC response times and ALC voltage requirements vary with different manufacturers Operating Instructions And Guidelines Front Panel Controls MULTIMETER Switch This four position switch selects either the plate voltage HV of 0 3500 volts the reflected peak envelope power REF of 0 500 watts the ALC detector output voltage ALC of 0 35 volts or the approximate ALC grid current threshold ALC SET of 0 350 mA See the Multimeter Functions section on page He more details OFF ON Switch This switch turns the main power off and on When this switch is placed in the ON position the fan should start the meters should be illuminated and high voltage should appear 13 AL 80B Instruction Manual STBV OPR Switch This switch disables the amplifier s internal antenna relay In the STBY position the amplifier is bvpassed without turning the tube s filaments or the power supplv off This switch will also reset the grid protection circuit if an optional grid overload protection circuit is installed The overload circuit will be reset whenever this switch is placed in the STBY position and returned to the OPR position PLATE Control The PLATE control adjusts the output tank circuit to resonance This control should always be adjusted for maximum RF output power Maximum RF output power normally occurs simultaneously with maximum grid current and
20. cted to an outlet 12 AL 80B Instruction Manual Interconnections 1 Connect the exciters RF output to the RF IN connector on the rear of the AL 80B with 50 ohm coax Use any good quality 50 ohm cable long enough to connect the amplifier to the exciter This amplifier connection uses a standard SO 239 female that mates with a PL 259 male connector on the cable 2 Connect the existing station antenna system to the RF OUT connector on the rear of the AL 80B with RG 8 type coax This amplifier connection uses a SO 239 female that mates with a PL 259 connector on the cable 3 Shielded audio type cable with a standard male phono plug should be used to connect to the RLY jack on the AL 80B This jack has positive 12 Vdc open circuit and supplies 100 mA of current when pulled to ground The relay circuit has an internal back pulse canceling diode to protect sensitive exciter circuits from damage 4 Connect a short wide smooth ground lead from a good earth and RF ground to the rear panel GND terminal Avoid using braided conductors for ground leads 5 The 12 V connection on the rear panel provides 12 Vdc at 200 mA maximum to operate external dial lamps or accessories such as the ATR 15 Antenna Tuner 6 Connect the ALC jack to the ALC input of the exciter with a shielded cable and a phono plug The proper connection point on the exciter should be indicated in the exciter s manual The AL 80B ALC will operate with any exciter th
21. e current Ip should now dip slightly The drive power should be removed 20 AL 80B Instruction Manual lla Increase the ALC SET voltage if the ALC is connected until 180 mA 18 volts is indicated Applv full drive not to exceed 100 watts and adjust the LOAD and PLATE controls for maximum RF output power The grid current should not be allowed to go above 200 mA at this stage The plate current should not be allowed to exceed 600 mA during brief periods of tuning 15 seconds 11b Increase the exciter drive power if the ALC is not connected until 180 mA of grid current is indicated Adjust the LOAD and PLATE controls for maximum RF output power The grid current should not be allowed to go above 200 mA at this stage The plate current should not be allowed to exceed 600 milliamperes during brief periods of tuning 15 seconds 12a For CW operation the output power should be reduced with the ALC SET control until the rated output power of 800 watts is obtained The LOAD control should be adjusted until minimum plate current is obtained without dropping below 800 watts The exciter s power can be reduced until the multimeter shows a slight upward flicker with the MULTIMETER switch in the ALC position if the ALC is used 12b For SSB operation the ALC SET should be adjusted to allow 200 mA of grid current near the 20 volt marking The exciter should be set to produce maximum output power not to exceed 100 watts of
22. e transformer primary if the top cover is removed WARNING High voltage can kill Accidental contact with the voltages in this amplifier can be lethal For your personal safety please observe the following precautions NEVER defeat the interlock NEVER remove the cover with the amplifier connected to the power line ALWAYS allow several minutes for the capacitors to discharge after unplugging the amplifier and before removing the cover 4 ALWAYS select the high voltage HV function of the Multimeter to check the high voltage potential Do not remove the cover if voltage is indicated 5 ALWAYS ground the tube anode top metal conductor to the chassis before touching anything inside the amplifier 6 ALWAYS be cautious of heat Many components inside the amplifier operate at high temperatures 7 NEVER make any unauthorized component or circuit modifications to this product The only acceptable source for modifications is Ameritron or a source approved by Ameritron Unauthorized modifications almost certainly will increase the risk of equipment failure or personal injury p prm AL 80B Instruction Manual Circuit Descriptions ALC The AL 80B is one of the few amplifiers using a true automatic level control ALC circuit In this amplifier the ALC actually samples grid current and power supply loading to determine the ALC voltage The front panel ALC SET knob adjusts the level of grid current where ALC action begi
23. ed from minimum while speaking until the plate current Ip just flickers upwards The plate current Ip should be around 100 mA on these flickers 9 Place the MULTIMETER switch in the ALC SET position Adjust the front panel ALC SET control until the multimeter indicates 10 volts This adjustment will limit the amplifier s grid current to approximately 100 mA STEPS 10a and 11 REQUIRE A CONNECTION FROM THE AMPLIFIER S ALC OUTPUT TO THE EXCITER S ALC INPUT STEPS 10b and 11b SHOULD BE USED IF THE EXCITER AND AMPLIFIER ALC LINES ARE NOT CONNECTED Note Step 10 requires the simultaneous observation of the plate current 1 and the grid current Ig 10a the ALC line is connected adjust the exciter s drive or power output control to maximum NEVER ALLOW THE GRID CURRENT Ig TO EXCEED 120 mA OR THE PLATE CURRENT Ip TO EXCEED 400 MILLIAMPERES AT THIS STAGE OF TUNING If either current exceeds these limits reduce the ALC SET control Adjust the PLATE control for maximum output power The plate current Ip of the amplifier and the output power of the exciter should dip decrease when this adjustment is made 10b Ifthe ALC is not connected place the exciter in the transmit mode and gradually increase the drive until a grid current of 100 mA or a plate current of 400 milliamperes whichever is higher appears The PLATE control should be adjusted until maximum grid current and maximum RF output power appear The plat
24. erates directly from 120 Vac power lines Ameritron also offers an internal QSK board as a space saver for the AL 80B This internal board is slightly less expensive However it provides less flexibility and serviceability than the external QSK 5 unit Factory installation of the QSK 5PC is highly recommended Contact Ameritron for details on the QSK 5 and the QSK 5PC Periodic Maintenance The high voltage present on various parts of the amplifier will attract dust and dirt The high voltage areas at the bottom of the plate choke and the plates and insulators of the air variable capacitors should be kept dust free These areas should be inspected periodically especially if the amplifier is operated in a dusty environment These areas may be inspected by unplugging the line cord and waiting a few minutes for the power supply capacitors to discharge The high voltage should then be checked with the internal multimeter by placing the meter switch in the HV position WARNING High voltages can kill Accidental contact with the voltages in this amplifier can be lethal 23 AL 80B Instruction Manual For vour personal safetv please observe the following precautions 1 NEVER defeat the interlock 2 NEVER remove the cover with the amplifier connected to the power line 3 ALWAYS allow several minutes for the capacitors to discharge after unplugging the amplifier and before removing the cover 4 ALWAYS select the high voltage HV funct
25. h any tuning or drive adjustment 15 AL 80B Instruction Manual During CW operation the ALC SET control voltage should be adjusted just high enough clockwise to allow the desired output power to be reached The ALC SET control should never be adjusted to the point where the grid current can exceed 200 mA under any tuning or drive adjustment condition During proper CW ALC operation the exciter drive level control should be adjusted until the ALC voltage meter slightly flickers ALC position of the MULTIMETER switch while operating with normal output power levels The ALC circuit will limit the amplifier s grid current to a safe value if anything accidentally changes in the station or the antenna The CW keying waveform of the radio will remain unaltered when the ALC is adjusted in this manner Caution should be exercised if the ALC SET is used to control the CW power output with the exciter power control set at maximum Key clicks may be produced if the exciter has a poor ALC response time Check for proper wave shape when using the ALC in the amplifier exclusively to control the RF output power Rear panel ALC LIMIT control The ALC Limit control rear panel limits the maximum voltage available from the ALC circuit This control is necessary only because the ALC response times and voltage requirements for exciters have never been standardized The ALC voltage requirements may even vary between different models produced by the
26. ion of the Multimeter to check the high voltage potential Do not remove the cover if voltage is indicated 5 ALWAYS ground the tube anode top metal conductor to the chassis before touching anything inside the amplifier 6 ALWAYS be cautious of heat Many components inside the amplifier operate at high temperatures 7 NEVER make unauthorized component or circuit modifications to this product The only acceptable source for modifications is Ameritron or a source approved by Ameritron Unauthorized modifications almost certainly will increase the risk of equipment failure or personal injury The cover should be removed and a low value 40 to 500 ohm two watt or larger resistor should be secured to the chassis The other end of this resistor should be connected to the tube anode with an insulated clip lead CAUTION NEVER ground the anode directly to the chassis without a series resistor Component damage may occur from the current surge Note This resistor is a safety device that must be installed when beginning service work and removed when the work is finished Dust and dirt can be blown out of the amplifier with a shop vacuum or a high pressure air hose A soft bristle brush dipped in alcohol can be used to clean particularly dirty areas If the amplifier is operated in a dusty environment a non conductive low restriction foam air filter can be placed over the ventilation holes on the left side of the cabinet near the filter c
27. ions are as follows ALC In this position the multimeter measures the output voltage of the ALC detector The full scale reading of the ALC detector is 35 volts It is read directly from the ALC HV scale of the multimeter The multimeter will indicate the maximum value of ALC voltage available from the internal ALC circuit The meter should flick upwards occasionally during normal ALC action in this position 14 AL 80B Instruction Manual ALC SET In this position the multimeter measures the approximate grid current that will produce ALC activity One zero must be added to the reading on the ALC HV scale for this function For example If the meter reads 15 add one zero 150 In this example ALC action will begin at approximately 150 mA of grid current ALC Controls The position of the ALC SET control determines the grid current value that will begin to produce ALC voltage Rotating the ALC SET control counter clockwise reduces the maximum grid current obtainable and the available RF power output Rotating the ALC SET control clockwise increases the maximum grid current level The approximate grid current available before ALC action begins can be determined by placing the MULTIMETER switch in the ALC SET far clockwise position The ALC SET control should normally be adjusted to produce a multimeter reading of 12 to 18 volts with the MULTIMETER switch in the ALC SET position This will allow a maximum grid current of app
28. is designed to operate at very high temperatures These temperatures normally produce a dull to bright red anode color This is a normal operating condition The anode is coated with a getter material that de gasses the tube This material is activated by the high anode temperatures The likelihood of a long term gas failure is reduced by operating the 3 500Z with a slight amount of anode color Care must be taken to avoid exceeding the temperature ratings of the tube s glass to metal seals The life of the tubes in this amplifier may be prolonged if tuning periods are kept short and a brief cool down periods are provided between tuning periods Try to allow a one or two minute non transmitting cool down period after lengthy CW or RTTY transmissions before shutting off the ac power switch Incorrect operation is most likely to damage the tube s control grid or anode Applying full drive power for several seconds with excessively light loading can cause control grid damage Several seconds of high drive power operation with improper tuning or excessively heavy loading can melt or damage the anode These conditions can be avoided by following the tuning procedures in this manual In the AL 80B a grid current of 250 mA at 100 watts of drive produces the rated grid dissipation of 20 watts For maximum tube life the grid current and drive power should always be kept below these values WARNING NEVER drive this amplifier with more than
29. itch 507 1157 Rocker Switch 507 1150 Interlock Switch 504 3247 33 ohm 1 4 watt 100 1330 Transistor MJF 3055 305 3055 406 1109 2C 3 500Z Tube 350 0167 r C56 50 0080 1 50 0080 50 0080 3 50 0080 4 50 0080 5 REC RFC3 28 AL 80B Instruction Manual Frequency Coverage AL 80BX 1 8 2 0 MHz 3 3 4 4 MHz Operation on 11 13 MHz 15 5 16 5 MHz and 25 27 9 MHz will damage components Amplifier Tuning Log Fill in this log with the amplifier settings to quickly change bands Use a pencil as settings may change with different antennas 29 AL 80B Instruction Manual Notes 30 50 0080 2 Tuned input TT enses 1 9949 FTIIT 1 YUM i 50 0080 1 su SATIIANNIS JAAA 2 dyo MOTIIM 911 1551034 ERAH 14904 4 5 5 sMd 31 I5 0800 06 201418 YEL YEL BLK YEL 9214 D ij 3 2 pelo erra SZ SZ 8110 2119 cet 2 12 6 8119 et 9 1 01 6 1 6119 9 12 m So dpi 812 sala 0212 4 0112 2010 A 2 1219 I 9118 S 2113 601 Ad ota pio cela NL p 3 4212 2212 4118 6814 225
30. meter just flickers AM Amplitude Modulation Operation The efficiency of any conventional linear amplifier must remain below half the peak efficiency under maximum signal conditions less a safety factor in AM operation Since this linear amplifier has a peak plate efficiency of nearly 65 the carrier efficiency must be kept below 30 to maintain linearity The power dissipated in the tube anodes will be more than twice the carrier output power The carrier power must be kept below 200 watts for clean and safe AM operation With 200 watts of carrier the peak envelope power will reach 800 watts with 100 symmetrical modulation The modulated AM power output should be limited to 1000 watts peak with non symmetrical modulation that enhances the positive peaks FM Frequency Modulation RTTY and Digital Operation The efficiency of this amplifier will approach 65 in the FM RTTY and Digital Operation modes Since these modes do not require linear amplification of complex waveforms the tuning can be re adjusted for maximum power at the desired output power level This will keep the efficiency as high as possible Audio Distortion One problem that often occurs when using a linear power amplifier is SSB audio distortion on one or more bands This distortion is usually caused by RF feedback from either a poorly designed antenna or poor RF grounding REMEMBER THAT A GOOD GROUND FOR DC IS NOT NECESSARILY GOOD FOR RF RF circuits require short c
31. n Manual ALC Limit Adjustment rear panel This adjustment procedure should be used if pumping occurs from excessive transceiver ALC sensitivity and or slow transceiver ALC response time 1 Load the amplifier for maximum output on any band see tuning instructions later in this manual 2 Adjust the ALC SET control on the front panel and the rear panel ALC Limit potentiometer to their full counter clockwise positions 3 Apply full exciter drive power and adjust the rear panel ALC Limit potentiometer clockwise rear view until the amplifier s ALC output voltage meter multimeter ALC position indicates 6 to 10 volts As an alternative the potentiometer can be adjusted clockwise until the RF output power reaches 300 500 watts 4 Adjust the front panel ALC SET control to the desired power level Driving Power This amplifier is designed to operate at full ratings when it is driven by an exciter that has approximately 70 watts of RF output An exciter with a lower output power may be used with a resulting decrease in amplifier output Both the driving power and the LOAD control must be carefully adjusted when using an exciter that delivers more than 70 watts Proper control settings will help prevent excessive grid current and spurious signals which create needless interference to other operators A monitor scope is recommended for continuous output observation An oscilloscope is the best way of determining if the amplifier is
32. ns ALC action begins softly over a range of a few milliamperes to minimize distortion This soft touch ALC is an Ameritron exclusive The ALC circuit is located on the METER BOARD P N 50 0080 3 behind the MULTIMETER switch IC301 pins 9 and 10 compares the voltage drop caused by grid current across R106 in the main power supply board ALC voltage is derived by comparing the grid shunt voltage to the voltage from the power supply The output of ICI pin 8 will go negative if the grid shunt voltage exceeds the voltage from divider R311 and R2 chassis mounted control or if the supply voltage sags from excessive line voltage drop Pin 8 is followed by current buffer Q303 that sources the negative ALC voltage to the ALC output jack This amplifier includes an ALC Limit control on the rear panel This control reduces overshoot and eliminates motor boating a slow rhythmic fluctuation in the transmitted signal These problems are caused by excessive transceiver ALC attack time delay This control sets the maximum voltage level available from the ALC circuit Adjustment details are given on page M Dynamic Bias Conventional bias circuits force high power linear amplifiers to dissipate hundreds of watts during low or no signal periods This creates needless heat since virtually no dissipation is required unless the amplifier is being driven with large signal levels The AL 80B contains an exclusive bias circuit that reduces the idling quie
33. onnections with smooth wide conductors Braiding or woven wire has a very high RF resistance and should be avoided See the Grounding section on page of this manual More detailed suggestions on grounding are available by requesting Amerit Tech Bulletin on RF Feedback 22 AL 80B Instruction Manual QSK Operation The antenna transfer relay in the AL 80B takes approximately 15 milliseconds to change states This precludes using the standard internal relay for QSK CW operation Commonly available vacuum relays are specified at 5 to 7 milliseconds of switching time Even expensive vacuum relays are less than ideal for high speed QSK operation At 60 WPM less than 50 of the receive time is available with vacuum relays On PACKET AMTOR and other modes delay can be added to the transmit and receive changeover to use either vacuum or our standard relay effectively Ameritron offers two high speed PIN diode options that permit operation on modes requiring high speed receive transmit switching Both systems offer noiseless switching times of under one millisecond Since PIN diode systems are several times faster than vacuum relay systems they allow over 90 of the available receive time to be used at 60 WPM Ameritron highly recommends using the external QSK 5 switch This stand alone PIN diode switch can be used with almost all types of amplifiers and transmitters Modifications are not required in amplifiers used with the QSK 5 unit The QSK 5 op
34. pe Power vs Average Power Peak envelope power PEP is often misunderstood by amateurs PEP is not associated with the sine wave or root mean square RMS power and PEP has no fixed ratio to average power on any mode except FM FSK or CW It is impossible to use a formula or rule of thumb approximation to convert between average and peak voice waveform powers PEP is the power at the crest highest point of the RF envelope waveform On SSB the average power can vary from a few percent of the PEP to over half of the PEP Generally the PEP on SSB is two to five times greater than the average power A 50 watt average power SSB signal could have peak envelope powers that are lower than 100 watts or that exceed 250 watts On CW and other constant amplitude modes such as FM or RTTY the PEP is always equal to the average power On CW FM or RTTY 1000 watts of average power produces exactly 1000 watts of PEP AL 80B Instruction Manual Tube Life The 3 500Z is a reasonably rugged tube The primary concern in this tube are element failures from excessive temperatures Element temperature is a function of the duration and the amount of power dissipated The elements in the 3 500Z have very good immunity to short term overload failures The anode in the 3 500Z can tolerate large dissipation overloads for short periods of time due to the thermal mass of the anode Anode color is a good indication of correct tube operation The anode in the 3 500Z
35. peak power Next the amplifier s LOAD and PLATE controls are adjusted for maximum power output on the internal peak reading RF wattmeter with either a two tone generator or sustained HEL L L L L O driving the exciter The ALC SET control should then be reduced until the peak power output is slightly lowered Finally the exciter s audio gain or output power is adjusted until the multimeter ALC position indicates the desired ALC level This setting should normally allow around 150 mA grid current on a steady carrier or whistle Note If the ALC is not connected the amplifier must be fully loaded for maximum output with maximum drive not to exceed 100 watts The exciter s output should then be reduced until 1000 watts PEP is obtained ALC SET control Proper adjustment of the front panel ALC SET control accomplishes the following 1 Exciters power is limited to a value that produces a predetermined maximum grid current in the amplifier The front panel ALC SET control determines the maximum grid current obtained 2 The LOAD control setting determines the maximum plate current and output power for a given grid current Never exceed 600 mA of short duty cycle or 400 mA of long duty cycle plate current Never exceed 200 mA of operating grid current 3 For normal SSB operation the exciter power should be reduced until the ALC voltage measured in the ALC multimeter position flicks upwards on occasional voice peaks This
36. r by installing the corner screws first Install all the screws loosely until every screw is in place Tighten the screws after they have all been installed Note Save all packing materials for future shipping The packing materials used to ship this amplifier are specially designed to prevent damage Replacement packing materials may be purchased from Ameritron if original packing materials are unavailable Ameritron will NOT be responsible for re shipping damage due to improper packing li AL 80B Instruction Manual Ameritron AL 80B 1000 watt PEP Linear Amplifier Instruction Manual EG AUTOS tat L 1 AL 60B Technical Specifications He I Sanaa toate eae ede ud cad 2 ntfrodu tion 3 Safety Mterl 3 D6SCHIDEDHSG cas A rss a aa 4 M EE 4 Dynamic Bias ao gea uel cd e doctae e c i bread eed eda 4 Power SUPPLY 5 Filament Supply M 5 HVJ SUDDIN sea i ata r asta sss Sas 5 MeterS A a 5 Current Meter plate and grid Seales 5 ote tat unn u dg titlu 6 Multimeter Functions g A a eo As edt 6 Wattmeter Circuit a anasu ede abate 7 Peak Envelope Power vs Average POWet ie eiii a f ip pee diode 7 Eolo TES ER
37. r or in the basement of a structure 6 choke baluns should be used on all coaxial feedlines The feedlines should be coiled into several 4 to 6 diameter turns before they enter the building Either directly bury the feedlines a few inches deep in the ground for a minimum distance of ten feet or ground the shields to a separate earth ground on the antenna side of the choke 11 AL 80B Instruction Manual Transformer Connections The power transformer of the AL 80B has fourteen different voltages available on the primary and is rated at full power on frequencies of 50 and 60 Hz The JUMPER CONNECTIONS chart below indicates the proper placement of jumpers for various power line voltages The high voltage secondary of the AL 80B has three leads The normal wiring is indicated on the circuit board silk screen by the initials R Y RED YELLOW and R G RED GREEN For low power operation the R Y and R G wire can be reversed This will reduce the plate voltage of the AL 80B to permit operation at output levels below 400 watts WARNING The AL 80B requires different back panel fuses for various line voltages Use the fuse listed above for maximum protection JUMPER FROM TOP LETTERS TO BOTTOM LETTERS IN COLUMN HIGHEST LINE LINE V G D F FUSE SlO OIN IN i Oo Factory wired Model AL 80B and AL 80BY Factory wired Model AL 80BX DANGER Never change jumpers with the power cord conne
38. readings at all stages of the tuning procedure are very important along with a complete description of the other equipment used with our product Written assistance is also available Due to time delays in processing mail please allow at least three weeks for a written reply For service or written correspondence use the following address AMERITRON 116 Willow Road Starkville MS 39759 Telephone 662 323 8211 FAX 662 323 6551 NOTE Service history has clearly shown that most problems are operating or installation errors rather than equipment failures Most problems can be resolved over the telephone Please contact our staff before shipping parts or equipment to us AL 80B Instruction Manual The packing materials used to ship this amplifier were speciallv designed to prevent shipping damage The original packing materials should be used to ship this amplifier Replacement packing materials mav be purchased from Ameritron if original packing materials are unavailable or damaged CAUTION Never ship this amplifier with the tube installed Ameritron will not be responsible for shipping damage caused bv improper packing Installation Guidelines And Suggestions Location Of The Amplifier Do not install the amplifier in excessivelv warm locations or near heating vents or radiators Be sure air can circulate freelv around and through the amplifier cabinet Provide an unobstructed cold air inlet for the amplifier DO NOT place an
39. roximately 120 to 180 mA ALC Adjustments During SSB operation two adjustments affect the ALC and the sound of the signal One is the exciter s microphone gain or RF output level adjustment It will control the fullness of the ALC and the average output power It will have very little effect on the peak output power however The fullness of ALC action is indicated by the multimeter reading in the ALC position More exciter audio gain or power output will drive the amplifier s ALC circuit harder and produce a more constant meter reading This produces RF compression that increases the talk power without increasing signal bandwidth or distortion Note Audio background noise will increase while using heavy ALC levels on SSB Objectionable background noise levels may occur while using heavy amounts of ALC especially if the heavy ALC levels are used in conjunction with other speech processing In these situations operating in a quiet room and close talking the microphone will minimize objectionable background noise The amplifier s ALC SET control determines the level of grid current that produces ALC activity the maximum power output level This amplifier has the best linearity when the ALC SET control is adjusted to limit the peak grid current to 150 mA or lower This adjustment must be made with a carrier or single tone signal When the ALC SET control is properly adjusted it will be impossible to exceed 150 mA of grid current wit
40. rted the overload circuit if used may repeatedly trip and the grid current may appear excessively high before full power is reached AL 80B Instruction Manual Multimeter The multimeter is the meter on the right It continuously reads the forward peak envelope power on its left hand scale FWD This scale is calibrated in 100 watt steps up to 2 kW The right hand scale of this meter provides four metering functions that are selected by the MULTIMETER switch These functions include the measurement of high voltage HV reflected power and SWR REF ALC voltage output ALC and relative ALC threshold ALC SET The MULTIMETER FUNCTIONS section that follows describes these functions in more detail Multimeter Functions HV The multimeter indicates the dc plate voltage applied to the PA tube when the MULTIMETER switch is placed in the HV position The correct scale to use is the ALC HV scale This scale has a picket every 100 volts Two zeros must be mentally added behind the numbers indicated on the meter scale i e multiply by 100 so that 25 2500 volts and 20 2000 volts Do not operate the amplifier if the high voltage is over 3200 volts with the amplifier on standby See the Transformer Connections section on page ira information on correcting excessive high voltage REF The multimeter measures the antenna or load peak envelope reflected power and the SWR when the MULTIMETER switch is placed in the REF position The full
41. same manufacturer If the ALC response time of the exciter transceiver is faster than the rise time of the RF envelope there will be no voltage compatibility problems The ALC voltage from this amplifier will automatically self adjust to the value required by the exciter If the ALC voltage requirements are low and or if the ALC attack time is slow the ALC may cause the output power to pump at a very slow rate The undesired pumping can be corrected by reducing the amplifier s ALC output voltage with the ALC Limit control R1 A full counter clockwise ALC Limit setting will produce approximately 10 volts of maximum negative ALC voltage A full clockwise setting viewed from amplifier rear will produce no ALC voltage Always start with this control fully counter clockwise before slowly advancing this control clockwise The ALC Limit Adjustment section that follows gives adjustment details An external 1 000 to 5 000 ohm potentiometer can be added from the ALC output line to ground if the particular amplifier you are using does not have a rear panel ALC Limit control The chassis shield of the amplifier s ALC output jack must connect to the clockwise shaft end view terminal of the ALC exciter voltage control The ALC jack center pin on the amplifier must connect to the counter clockwise terminal shaft end view of the external control The center of the control connects to the ALC input of the exciter 16 AL 80B Instructio
42. scale reflected power reading is 500 watts This scale is marked every 10 watts below 100 watts and every 100 watts from 100 to 500 watts The SWR of the load is measured when the MULTIMETER is in the REF position by observing the different red SWR curves The forward and reflected power meter pointers will cross each other on or near the correct SWR curve ALC The multimeter measures the output voltage of the ALC detector when in the ALC position The full scale ALC reading is 35 volts and is read directly from the ALC HV scale The meter should flick upwards occasionally during normal ALC action See ALC Circuit operation on page more information ALC SET The multimeter measures the approximate grid current that will produce ALC activitv when the meter switch is in the ALC SET position One zero must be added to the reading on the ALC HV scale for this function For example ALC action will begin at approximatelv 150 mA of grid current tvpicallv between 120 mA and 180 mA when the ALC SET control is adjusted until the meter reads 15 AL 80B Instruction Manual Wattmeter Circuit The AL 80B wattmeter circuit uses an accurate directional coupler followed by a true peak detector circuit This circuit will accurately determine the true peak envelope power PEP of normal voice waveforms If the load SWR is high the true power reading will be obtained by subtracting the reflected power from the forward power Peak Envelo
43. scent current very close to the tube s cut off region The power amplifier tube in the AL 80B has a full resting period of very low dissipation between dots and dashes on CW and between words on SSB The lower idling current reduces component temperature on both CW and SSB If only a few milliwatts of RF power are applied to the amplifier the quiescent current will increase Linearity remains excellent with this circuit because the tube can remain biased for class AB operation without unnecessary standing dissipation The dynamic bias circuit is located on the Power Supply Board P N 50 0080 1 Diodes D101 and D102 rectify a small sample of the RF drive voltage This voltage is applied to the base of dc switch Q101 If Q10I s base is driven with a few microamperes of current from the RF sampling circuit Q101 s collector will pull the base of PNP transistor Q102 low This turns dc switch Q102 on When Q102 is on zener diode D103 is connected between the collector and base of Q103 D103 sets the operating bias This zener applies forward bias to Q103 s base whenever the collector voltage of Q103 exceeds the voltage of D103 This forward bias will turn Q103 on harder and will reduce the collector voltage If the collector voltage is less than the breakdown voltage of D103 Q103 will move towards cut off and the collector voltage will increase Q103 functions as a current buffer for zener diode D103 AL 80B Instruction Manual Power Supplv Filamen
44. ssary stress in the tube s filament An accumulation of gas or stray debris in the tube can cause arcs between the anode and the other elements of the tube The resulting gas arc will generally manifest itself as a loud pop when the amplifier is first turned on A gas arc will often damage diode D117 on the negative rail of the filter capacitor bank and open the fuses in the amplifier If this problem occurs frequently the tube should be tested or replaced The use of low quality tubes tubes that have been stored for extended periods or abused tubes increase likelihood of a gas arc Ameritron recommends using only current code date Eimac 3 500Z tubes Export Modifications A simple modification will allow operation on frequencies above 15 meters Instructions for this modification are available by sending a written request for Export Modification Instructions along with a copy of a valid amateur license There is no charge for this information Export models are shipped with this modification installed and have an X or Y following the serial number Standard frequency ranges are indicated in the chart on PRETI Technical Assistance Technical assistance is available during normal central standard time business hours on weekdays Customer service is more effective when our engineers are provided the following information 1 Model and serial number 2 Date of purchase and dealer 3 An accurate description of the problem Meter
45. t Supplv The filament circuit of this amplifier satisfies all requirements of the tube manufacturer related to tube performance and life The filament voltage and inrush current are controlled bv the power transformers internal resistance and impedance filament choke resistance filament wiring resistance and the step start circuit NEVER replace any circuit components or wiring with substitute parts This precaution will insure maximum life for the tube Plate HV Supply The plate supply uses a full wave doubler circuit with 200 amp surge rated diodes and a heavy duty 26 pound grain oriented transformer Filtering is accomplished by a bank of high quality computer grade capacitors totaling 26 mFd Large 50k ohm 7 watt bleeders are used for safety and superior voltage equalization The transformer allows user selection of fourteen different line voltages see the Transformer Connections section on page ai for details Power is supplied through OFF ON switch 52 A 10 ohm resistor R27 limits the line current during the filter capacitor charge time to lower component stress When the filter capacitor charging current decreases sufficiently RLY 102 shorts the 10 ohm resistor This applies full power line voltage to the transformer The 10 ohm resistor is protected from high voltage supply shorts by a 2A slow blow fuse F101 during start up If F101 or the 10 ohm resistor R27 fails the amplifier will not start If F101 fails from a momentar
46. trol 2 Lightly loading an amplifier will also result in large voltages building up in the tank circuit Under loading an amplifier is much harder on the tubes and other components than operating a properly loaded amplifier into a high SWR or with excessive drive power 3 Never depend on average reading power or current meters to indicate proper operation on SSB or other linear modes The best indicator of linearity is either an oscilloscope or the internal PEP RF output meter Maximum linearity can be determined by finding the maximum output power possible and then reducing the exciter power for a slight reduction in output power 4 Never exceed 170 mA of grid current on CW carrier during actual operation The proper grid current for SSB will range from 0 to 75 mA The SSB grid current will vary with the operator s voice the amount of signal compression or processing and the tube characteristics Tuning Follow the instructions below in numerical order Proper tuning will produce excellent output power a clean signal and good tube life If the various meter readings are different than indicated in the text check the external amplifier connections Consult the manual for the exciter if necessary WARNING The transformer must be wired correctly for your line voltage This amplifier is normally shipped wired for standard 120Vac operation Refer to the Transformer Connection section on page Tuning Procedure Important Note If you
47. v books magazines or equipment that will impede the free flow of air on or near the cabinet ventilation holes Ventilation The AL 80B ventilation svstem has been designed and tested to maintain tube seal temperatures safelv below the tube manufacturer s rating at 500 watts of continuous carrier output or 800 watts of continuous two tone or CW power output when the amplifier is properlv tuned The fan in the AL 80B is a permanently lubricated type that requires no maintenance in normal operation To insure adequate cooling in your installation please observe the following 1 Do not block or unduly restrict the ventilation holes in the cover Be sure that the amplifier is located in an area so the ventilation holes have open air circulation It is particularly important to avoid restricting the air inlet 2 exhaust airflow is over 30 CFM Do not assist the exhaust airflow with cabinet mounted fans 3 The most efficient way to improve airflow is to pressurize the air inlet area Be sure that any fan used to assist the inlet airflow has at least a 60 CFM rating 4 The exhaust air will become quite warm at high power levels Do not place any heat sensitive objects in the exhaust air stream Power Connections The AL 80B is supplied with a NEMA 5 15P plug for 120 Vac operation Full duty cycle operation with ac supply voltages below 100 volts is not recommended The Transformer Connections section on page lisi adis the correct wiring
48. y HV to ground fault meter protection diode D117 may also fail See the Metering Functions section that follows for more information Meters Current Meter plate and grid The plate and grid current meter is located on the far left side of the front panel This meter indicates the plate current Ip on the right hand meter scale This scale has a small picket every 25 mA a large picket every 75 mA and indicates 750 mA at full deflection The left hand meter scale indicates the grid current Ig The small pickets on this Ig scale appear every 10 mA and the larger pickets appear every 50 mA The full scale Ig reading is 250 mA The plate and grid meters in this amplifier normally indicate maximum grid current and maximum RF output at or near the same PLATE tuning setting Maximum grid current and minimum plate current also generally occur at the same PLATE tuning setting NOTE If the grid and plate meters always track move together in exact step as the tuning controls are adjusted and if they show the same approximate amount of pointer movement diode D117 on the power supply board could be shorted D117 protects the overload circuit if used and the meters This diode is located near the electrolytic capacitors on outside edge of the main circuit board D117 will usually short if there is a large high voltage to chassis current fault The grid and plate current meters will not read correctly if this diode fails If D117 is sho

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