Tait Limited TEL0024 用户手册

C5.14

T856/857 Fault Finding

Copyright TEL

Y

N

Y

Y

Correct DC V

present on Q1 VCO?

N

Check inductors,

biasing resistors

& Q1.

Replace if faulty.

Go to B.

Loop filter &

components around

op. amp. (IC750) OK?

N

Noisy synth;

poor residual FM.

C

Isolate audio

modulation on VCO;

still noisy?

Trace audio fault.

Y

Y

N

Y

Y

Y

Change trimmer;

still noisy?

Change Q1;

still noisy?

Change TCXO;

still noisy?

Change varactors;

still noisy?

Replace VCO

assembly.

Synthesiser OK.

N

N

N

N

Y

VCO phase locked?

3-16V present on

control line?