Pioneer Amp DC-Z92/Tuner F-Z92 problem

[Cheuk-Fai Wong]

HI,

My Pioneer amp and tuner developed some intermittent problem which I do not
know if it is the amp or the tuner. There is no sound from the speaker when
the tuner is selected(may be a faint hiss if the vol is turned up to max.)
and the vu display shows no signal at the input. Some times the problem
disappear for a while and then the sound will be gone again. Any clue? or
any one can point me to a schematic or even pin out and volage levels at the
ribbon cable going from the tuner to the amp?

Thanks.

Cheuk

 

[Mark D. Zacharias]

Well, if you're referring to the signal strength meter, and it shows no
signal when the problem occurs, perhaps the antenna connection is loose or
connected improperly.

Mark Z.

 

[Cheuk-Fai Wong]

Hi Mark,

I checked the Ant connections and they are fine(AM and FM terminals). The
meters I am referring to are the VU meters.

Cheuk

 

[Mark D. Zacharias]

In that case, there may be an intermittent fault in the tuner - bad solder
connections, for example.

Mark Z.

 

[Cheuk-Fai Wong]

Dear Mark,

After inspecting the IC's used and downloaded their pinout and data sheets,
I proceed to chase the problem. When I look at the AM local osc I noticed a
100KHz higher/Lower(? I forgot) than expected when,say, I tuned to 1430KHz I
should expect 1430+450Khz but I notice the 100Khz difference. I think that
may be the problem. I could not measure the FM local osc because I do not
know where to measure. The unit uses LM7001(Sanyo PLL AM/FM synthesiszer),
LA1256 IF chip and AN7040 MPX chip. I do not have a local source to get the
LM7001 chip to replace so there is no way to prove my theory.

Thanks anyway.

Cheuk