Specifications

58
VISUAL
CHECK OF
THE BOARD
OK?
CORRECT
PROBLEM
4.2VDC AT
EMITTER OF
Q8?
CHECK VOLTAGE
REGULATOR
CIRCUITRY FOR
TX VCO
YES
YES
NO
NO
LOW OR NO POWER
AT INPUT TO P.A.
ARE Q201 &
Q202 BIASED
CORRECTLY?
CHECK R206,
R207, R208, R209
& L204
IS THERE RF
OSCILLATION AT
COLLECTOR OF
Q201?
CHECK
RESONANT TANK
(C207~9 & L203)
AND FEEDBACK
(C212 & C215)
SET LOWEST
FREQUENCY
IS CONTROL
VOLTAGE(TP1)
BETWEEN 1VDC
AND 3VDC?
CHECK
RESONANT TANK
(C207~9 & L203)
IS KVCO
BETWEEN 6MHZ/V
AND 7MHZ/V?
REPLACE C203
IS RF LEVEL AT
C218 BETWEEN -3
& 0DBM?
IS D201DC
BIASED?
IF R202 & L201 ARE OK,
MAKE SURE
SYNTHESIZER IS
WORKING CORRECTLY
NO
NO
YES
YES
YES
NO NO
YES
IF L205, COUPLING CAP. (C211, 213,
218) AND FEEDBACK (C212 & C215,
L204, R209) ARE OK, REPLACE LOW
GAIN DEVICE(S)
YES
NO
NO
YES
RF POWER IS OK BUT
NO OR INCORRECT
MODULATION
IF NO MOD.,
IS 1.9VDC AT
R201?
IS THERE
200mVrms SIGNAL
AT R201 UNDER
STANDARD TEST
CONDITION?
CHECK REF.
VOLTAGE
DRIVER (IC4A)
IS
1.9VDC AT
R201 FOR NO
MOD. IN?
IF R26, C19 ARE OK
CHECK ALL PARTS
AROUND IC3
IF R26, C19 ARE OK
CHECK ALL PARTS
AROUND IC3
IS THERE
DIFFERENT FREQ.
DEVIATION FOR
EACH CH FREQ.?
REPLACE INCORRECT
VALUE FOR C204, 205
AND L202
TROUBLESHOOT
DIGITAL BOARD FOR
SIGNAL PATH
YES
YES
YES
NO
NO
NO NO
YES
TX BUFFER(Q9) AND/OR DRIVER(Q10)
STAGE(S) BAD:
1)VERIFY GAIN FROM EACH STAGE.
2)REPLACE LOW/NO GAIN DEVICE(S)
Figure 9.5. Troubleshooting Flow Chart for TX VCO