Yaesu FT-901DM Maintenance Service Manual page 94

SERVICING
TRANSMITTER
Problem Condition Probable Cause(s)
(1) No power output (a) IC OK, but no * Defective L,, Lo2, Lis.
power output Shorted VCo,, VC.
Defective C7, Cs>
* Low bands only: Defective Co;—Coo,
Cro
* Defective RL;
* Open D,
(b) IC OK, but no | * Cold solder joint between band switch
output on a | and tank coil
particular band
Defective band switch
CW keying
*
associated circuit
(c) No IC indication * Defective 6146B
| * ACC plug not correctly wired or
improperly seated
* No screen voltage at 6146B because of
defective Lig93, band switch, or mode
| switch
|
(d) Idling IC OK, but no * Defective 1L2BY7A
drive | * No screen voltage because of defective
Ri603 + Cisos » Risor. OF Risos
* Defective Qios, Qio7. OF Qro3
(2) Poor TX (a) No power output on * Defective X+o;
performance LSB only
(b) No power output on | * Defective X7o2
USB only
|
(c) Nopoweroutputon | * Defective RL7:, Qzos
both USB/LSB | * No vox operation: defective or
grounded MIC or PATCH jack
| * Defective Qo, or Cro9
(d) No power output on * Defective X13. Qr0a , Qro1
CW/FSK/AM/TUNE |
(e) Keyer OK, but no | * Defective mode switch, Qisos, and
Defective Deos if carrier hangs up.