Cobra 200gtl Service Manual
Cobra 200GTL DX
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Cobra 200GTL DX
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Preliminary Information (There will be updates)
Cobra 200GTL DX
SET DC POWER SUPPLY VOLTAGE AT 13.8VOLT DC.
WATTMETER (50 OHM) TO THE ANTENNA CONNECTOR
PLL CIRCUIT ALIGNMENT PROCEDURE :
(1)
SET TRANSCEIVER TO FREQUENCY 28.000MHz
(2) WHILE IN RECEIVER MODE, CONNECT OSCILLOSCOPE DC PROBE TO TP1 (SEE
PARTS LOCATION).
(3) ADJUST T712 AND OBSERVE THE DC LEVEL SWING BETWEEN 0.2 TO +7 VOLT DC.
THEN SET THE DC LEVEL TO 2.8 VOLT
(4)
CHANGE TO TX MODE, CHECK THE DC LEVEL SHOULD BE < 6V
(5) WHILE IN RECEIVER MODE, CONNECT OSCILLOSCOPE DC PROBE TO TP2 (SEE
PARTS LOCATION).
(6) ADJUST T713 FOR MAXIMUM LEVEL
(7)
SET RECEIVER TO FREQUENCY 28.000 MHz.
(8) WHILE IN RECEIVER MODE, CONNECT FREQUENCY COUNTER PROBE TO TP2
(SEE PARTS LOCATION).
(9) SET THE FREQUENCY 28.000MHz BY MOVING TUNE SWITCH THAN ADJUST IFT T711
TO FREQUENCY 17.305MHz
CARRIER OSCILLATOR PORTION PROCEDURE :
(1) SET TRANSCEIVER TO FREQUENCY 28.000MHz
(2) CONNECT FREQUENCY COUNTER TO TP3 (SEE PARTS LOCATION).
(3) WHILE IN TRANSMIT AM/FM MODE. ADJUST T716 TO OBTAIN 10.695MHz READING.
(4) WHILE IN RECEIVER USB MODE ADJUST T714 TO OBTAIN 10.6975MHz READING.
(5) WHILE IN RECEIVER LSB MODE ADJUST T715 TO OBTAIN 10.6925MHz READING.
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Preliminary Information (There will be updates)
Cobra 200GTL DX
RF AMP CIRCUITS ALIGNMENT PROCEDURE :
1.RX ALIGNMENT
-AM
(1)
CONNECT THE PROBE OF RF SIGNAL MEASURING EQUIPMENT BETWEEN GROUND
AND ANNTENA POINT. SET THE SINAD OF SSG TO -47dBm AND THEN ADJUST
T703, T704, T705, T706, T707, T708 AND T710 FOR MAXIMUM READING ON THE
EQUIPMENT.
(2)
WHILE THE SSG AMPLITUDE IS AT -47dBm ROTATE THE SQUELCH KNOB AT
MAXIMUM LEVEL THEN ALIGN RV2 FOR SQUECLH, IT MUST BE 1000 ìV ± 500 AND
HYTERISIS OF 1-5 dB.
(3) AT BAND D MODULATION OFF ALIGN THE S-9 BY RV15 THE UNIT SHOULD OBTAIN
100 ìV READING.
(4)
CONNECT THE TEST PROBE TO THE COLLECTOR OF Q6 AND TURN ON THE NB
TESTER AND ALIGN THE T701 RX NB IT SHOULD READ < 3 dB.
-FM
(1) CHANGE TO FM BAND. SET THE SINAD OF SSG TO - 47dBm AND THEN ADJUST T702
MAXIMUM READING ON THE EQUIPMENT.
2.TX ALIGNMENT
(1)
TEST EQUIPMENT CONNECTION. CONNECT RF POWER METER, RF VTVM AND
OSCILLOSCOPE TO ANTENNA JACK.
MAKE SURE 13.8VDC AT PCB DURING TX.
(2)
TRANSISTOR NO SIGNAL BIAS CURRENT CONTROL PROCEDURAL TUNE THE
CHANNEL BAND TO BAND D WITH FREQUENCY 29.7000 MHZ THE UNIT SHOULD BE
AT HI POWER MODE MODULATION OFF AT LSB.
PRE DRIVER BIAS
CONTACT CURRENT TESTER PLUG TO CON 3 OF PIN C (+), PIN D (-).
THEN ADJUST CURRENT TO 60mA BY CONTROL RV19.
DRIVER BIAS
MOVE CURRENT TESTER PLUG TO CON 3 OF PIN A (+), PIN B (-) THEN ADJUST
CURRENT TO 1.3A BY CONTROL RV21.
(3)
THE UNIT SHOULD BE SET AT HI POWER MODE AM BAND MIC GAIN AT MAXIMUM
FREQ. @ 27.195MHZ.
(4) ADJUST T718, T719, T720, T721, T722, T723, AND L21 COILS TO OBTAIN THE
MAXIMUM INDICATION ON RF POWER METER.
CHECK AND READJUST FOR EQUAL POWER 26.065 TO 29.695MHZ.
(5) AT AM TX MODE AT HI, NO MODULATION ADJUST RV9 TO OBTAIN RF CARRIER
POWER OF 32 WATTS ON RF METER.
(6)
WHILE IN AM TX MODE HI/LOW SWITCH TO LOW, NO MODULATION
ADJUST RV8 TO OBTAIN RF CARRIER POWER OF 4W ON RF POWER METER.
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Preliminary Information (There will be updates)
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