OPERATOR'S MANUAL LINEAR AMPLIFIER
0 R. L. DRAKE COMPANY PRINTED IN U.S.A.
TABLE OF CONTENTS PAGE . . -~. ,................... ............................................... 1-1 GENERAL DESCRIPTION 12 . . MANUAL COVERAGE .................................................. CHAPTER 2 INSTALLATION ........................................................ 21 . . UNPACKING ........................................................... 22 . . TUBE INSTALLATION .................................................. 23 . . LOCATION .............................................................
.... .............. PAGE .............................. TUBE REPLACEMENT.. TEST EQUIPMENT ................................... AMPLIFIER TROUBLESHOOTING TUBE CHECK.. ................. ALIGNMENT PROCEDURES.. , INPUT COIL ADJUSTME METER ADJUSTMENT ...... ....................................... WATTMETER CALIBRATION, NULL ADJUSTMENT ... ................................... .................................. ................................... ..................................
LIST OF ILLUSTRATION'S Figure 1-1 MODEL L7 LINEAR AMPLIFIER 2-1 REAR CHASSIS CONNECTORS JUMPER CONNECTIONS FOR 120 VOLT OPERATION.. ........... JUMPER CONNECTIONS FOR 240 VOLT OPERATION.. ........... CONNECTING THE PS-7 POWER SUPPLY AND THE R. L. DRAKE LINE OF COMPATIBLE EXCITERS VIEWING ANGLE OPTIONS ...................................... FRONT PANEL CONTROLS L.. PLATE VOLTAGE AND PLATE CURRENT VS 1,000 WATTS DC INPUT POWER ............................................. SWR NOMOGRAPH ......................
CHAPTER 1 INTRODUCTION 1-1. GENERAL DESCRIPTION T h e R L. Drake Model L 7 Linear Amplifier offers con.tinuoas 2000 Watts PEP on SSB, and 1000 Watts DC on CW, AM (controlled carrier) and RTFY operation covering the ham bands 160 through 15 meters. Non-amateur frequencies between 1.8 and 21.5 MHz may be covered with mdi5cation of the input circuit. The L7 uses 2 zero-bias triodes in a Class B gmunded-grid circuit configuration that utilizes RF negative feedback for lower odd-order distortion products.
' 6 .>- Fig. 1-1 Model L 7 Linear Amplifier SPECIFICATIONS Frequency Coverage: Ham bands 160 through 15 meters. Non-amateur frequencies between 1.8 and 21.5 MHz may be covered with some modification of the input circuit. 2000 Watts PEP on SSB Plate Input: and 1000 Watts DC on CW, AM and RlTY. Drive Requirements: 100 Watts PEP on SSB and 75 Watts on CW, AM and n m r IbLLI.
CHAPTER 2 WARNING The L 7 has been designed incorporating several interlocks to prevent dangerous electricalshock. However, it is possible to disconnect the high voltage terminal while the L 7 is turned on. This is EXTREMELY DANGEROUS and never should be attempted for a m reason. When disassembling the L 7, the high voltage terminal should be disconnected LAST and at reassembly the high voltage terminal should be connected FIRST.
2-4. POWER REQUIREMENTS 2-8. MATCHING NETWORK The L 7 is furnished with its own separate Power Supply which can be operated from either 120 VAC or 240 VAC 50-60Hertz. Because of the large variety of plug and socket configurations for 240 volt service, and because the L 7 can be operated from either 120Volts or240 Volts, a line plug is not furnished with the L 7. TheL 7is shippedfrom the factory with jumpers connected to operate on 240 VAC.
2-12. VOX RELAY Aphono jack on therearoftheL7AmpMerkpm vided for connection to a paiT of norma& open relay contacts in the exciter, which doseontrans mit and thus turn on the arnpliik ar the same time The L7 is supplied with a cable with phom, plugs on each end for this pnrpase AGcandPS7 Power Supplies are equipped ui+h a -'pin connector instead of a phono jackforthistion.
TYPE ACCEPTANCE LABEL . .... .: -. I . .I I .~, . . .. - . . - ; L. ,e; . HIGH VOLTAGE CONNECTOR J5 - = <;,i . ; I n ' : CONNECTOR J4 J6 Fig.
120 VOLT Amplifier OPERATION Power Supply --Figure 2-2. Jumper Connections for 720 Volt Operation 240 - ..*<: - --- .. Power Supply ...- . -- ? ..-. -.+- Figure 2-3. . Jumper Connections for 240 Volt Operation . : ; -. ~~ ... . ~ OPERATION - Amplifier - VOLT -- .. - .+ - - . - ~~ I.: . ~ _ - . . - .
Fig. 2-4 Connecting the PS-7 Power Supply and the R. L.
OPTION A i OPTION B I N V E R T E D FRONT FEET mi SUPPLIED WITH UNIT SUPPLIED WITH UNIT Fig.
. > NOTES
CHAPTER 3 OPERATION CAUTION DO NOT turn on the L 7 Amplifier with the cabinet removed because the high voltage inter-lock shorts out the B+ and will damage Power Supply components. DO NOT operate the Linear Amplifier until it has been connected to a 50 Ohm antenna or a 50 Ohm Dummy Load. Be sure that the correctjumper connections described in Chapter 2 have -- - been made in both the Linear Amplifier and the Power Supply for the line voltage to be used. 3-1.
- FIGURE 3-1. FRONT PANEL CONTROLS I . Multimeter: Indicates plate voltage, grid current, and forward or reflected watts as selected by meter switches (8). 2. Plate Current Meter: Indicates plate current. 3. Indicator Lamps: Indicate standby or operate condition, SSB (highpower) mode, and multimeter function. 4. STBY Switch: When depressed, allows standby operation with the exciter connected straight through to the antenna. 5. AGC Control: Adjusts the transmitting AGC threshold. 6.
220 mA of grid current with the LOAD control until 0.565 plate Amperes is reached. Leave the exciter power a t this level and redip the plate current with the PLATE control and then bring the grid current back to 220 mA with the LOAD control. The L 7 will be very close to being tuned up and only small adjustments of the driving power, and PLATE and LOAD controls will be necessary to obtain 0.565 plate Amperes with 220 mA grid current a t resonance.
instead of the 3000 Watt scale. When returning the amplifier to service, be sure toreturn theMeter switch to 3000 Watts or the wattmeter may be damaged. The amount of RF power delivered to the load can be determined by subtracting the reflected power from the forward power. -.=/''- . ,+ :* .Jy =-- ..>-: .: = .. . .- .:, - -: : 3-10. OPERATION ON ACCESSORYkyS 2 =i.z .=... . ~ ..+-4 . .--.. -FREQUENCIES . . -. Bandswitch Position Freauencs in MHz 3:<7.
1000 W a t t s D C . Input VS Plate Voltage and Plate Amperes 1900 . . .".' - . .. - .. -.. . . -.- 1800 .-. . .. PLATE VOLTAGE PIATE AMPERES Figure 3-2. . - - Plate Voltage and Plate Current VS 7,OYIO Wans DC Input Power mawup 'OmC - Imo 7Q - YO- - so- - ¶a- ---P-30- 100 70 V.S.W.I. m r.ntn u-1.. " SW.R. CALCULATOR R. I.. DRAKE CO. MIAMISBURG.OHl0 Figure 3-3.
NOTES
CHAPTER 4 THEORY OF OPERATION 4-1. INPUT 4-3. STANDBY CUTOFF BIAS Refer to the schematic diagrams figures 5-4 and 5-5. The 50 ohm input is matched to the final amplifier cathodes by a pi-network on each band which is selected by the input switch S1. Theinput switch is ganged to the plate circuit bandswitch SIB. Negative feedback in the L 7 Amplifier is obtained by slightly raising the grids above ground with capacitors C19, C20, C21, C24, C25, and C27.
NOTES
CHAPTER 5 MAINTENANCE 5-1. SERVICE DATA Your L 7 will be checked and aligned a t the factory for a nominal fee if it has not been tampered with. Transportation charges are extra. Any necessary repairs will be made on a time and material basis. Please write or call the factory for authorization before returning your unit for alignment or service. Address your request for authorization to: R. L.
b. 50 Ohm SWR Bridge c . Standard Milliammeter (400 mA) d. RF Wattmeter such as R. L. Drake Model WH 7 or an RF Voltmeter such as Hewlett-Packard Model 410B or Boonton Model 91CA. e. Transmitter with variable output to 100 W CW at 14 MHz. f . 50 Ohm Dummy Load g. 1-1/2 Volt Battery h. 10 Ohm Potentiometer i . Insulated Alignment Tool 5-7. AMPLIFIER TROUBLESHOOTING Careful consideration has been given to the design of the L 7 to keep maintenance problems to a minimum.
m. Turn off the Amplifier, disconnect the Power Supply from the power source, replace the jumpers removed in step c above, remove the SWR bridge and replace the covers on the Power Supply and the Amplifier before resuming operation. 5-1 1. METER ADJUSTMENT To adjust the meters on the front panel of the L 7 proceed as follows: a. Disconnect the Power Supply from the power source. b. Remove all connections to the amplifier. c.
.. .. -. p . ., . with the standard wattmeter or with the RF power calculated from the RF voltage measured across the 50 Ohm load. After completely disconnecting all sources of power, the bottom cover of the Power Supply can be removed by taking out all of the screws around the bottom of the chassis. 5-16. 3000 WATTS FORWARD a. After the 300 watts forward calibration, set the L 7 bandswitch to 20 meters and tune it up as described in Chapter 3, "Operation.
PARASITIC CHOKES (PC-1, PC-2) RF PLATE CHCUE (RFC-4) - GRID &RENT CAL. POT. R-19 Fig.
I 120/22(1V mMINAL STRIP (SEE FIG 2-3) \ LOW P A S FILERS FILTER Fig.
1.5 VOLT L 7 CHASSIS 10n POT TEST PT. A M 0-400 MA MlLLlAMMETER R, PUSH BUTTON BOARD Fig. 5-3 Connections for Grid Current Meter Calibration RtJ TNmU llf 6 I R E I S O X , HY 7w I20 V ISA QR 24OV Ra POWER @POWER LINE GND POWER CONNECTOR SHOWN FROM SOLDER CONNECTION E N D Fig.
NOTES
.. Cornp~nsntLocations 35 2 4 .i 2 1 R A2 3 4 7 8 11 8 13 12 14 9 28 16 17 I8 6 "28 22 25 4 8 5 7 8 8 30 21 68 24 z7 7 30 SO 28 27 8 32 80 35 38 34 37 11 9 10 2o 36 39 41 45 58 40 44 61 48 9 11 10 . 12 47 13 14:: 81 52 15 17 48 42 43 48 50 22 2 5 : ; 21 24 63 5654 6268 27 28 6367 15 NOTE 17 UNEAR AMP Schemrtic Wpadtmlnarked1.Om2400arehpl.~dC.p.cltor.n*r*.d.W1to.l uahmfd-emr*rluraMd. Fig. 5-5 Model L 7 Linear Amplifier Schematic Diagram .
