HYT TC-446, Service Manual

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TC- 446 Service Manual
－
35
－
Repair Example
：
1) Symptom: no TX power; > 3A TX current;
Cure: replace Q31
2) Symptom: low TX power; Voltage at Q4, Q31, Q32 OK; 10mw power at Q31
（
RD07
）
IN; Around
1W power at D11;
Cure: replace Q31
2
、
No or low TX audio (test port for communication test set
：
AF OUT/AF IN)
N
Y
N
Y
是
N
Y N
Y N
Start
Inject 1KHz/100mv AF
signal into MIC plug;
±
4.2KHz
±
150Hz
modulation deviation?
Check MIC
plug and MIC;
Replace faulty
components;
Waveform input at
IC3(
NJM2100V
)
pin2 OK?
Check L14, C48, C169,
C168; Replace faulty
components.
In TX, amplified
waveform output at
IC3 pin7?
In TX, 5V
voltage at IC3
pin 8?
In TX, waveform
output at VR2?
Check IC3 and
peripheral
components;
Check the
connection to
Q4 C pin.
Check components between
VR2 and VCO (e.g.L10, R22,
C40); replace faulty
components;
Check Q24, Q25, VR2
(47K) and peripheral
components;