hifi engine

JVC JA-S22

Hello -

Recently bought a 'working JVC JA-S22 amp with a lovely sound', except it didn't have any. Too pretty to return, so I agreed a half price refund. The lights on the meters powered up but the relay didn't engage, so I removed it and checked its functionality - seems OK. Replaced all the caps on the power board except the two (expensive!) 8700uF ones which both appeared within tolerance. No difference - still dead inside.
I have limited skills and can solder and measure values, but real diagnostic skills are beyond my pay-grade. I am concentrating on the power board, but could the fault lie elsewhere?
Needless to say, I have cleaned and 'worked' all the switches and pots to the best of my ability, to no avail.
Any kind soul have any ideas?

oldnotbold



Re: JVC JA-S22

what are you using for an input and what position is the tape monitor switch on need more info. is anything showing on the vu meters, check for a speaker select switch. do the easy things first. describe "dead inside"

Re: JVC JA-S22

Sorry if this is a repetition - cannot fully grasp the responding sequence.
Apologies for my descriptive sloppiness - 'Dead inside' means that the relay still does not engage.
There is no indication at all in any of the Vu meters no matter what input (record deck, tuner or aux) I use, and the position of the tape deck switch, and everything else I try, has no effect on activating the relay.
Any readings that I have obtained seem to bear no relation to those quoted in the downloaded workshop manual.
Best wishes.

Re: JVC JA-S22

In the JVC JA-S22 there are two power IC (STK-0040). Mesure the DC voltage at pins 3 and 8, on both STK, with reference to ground (chassis). Voltage at these points should be low, only a few milivolt. Anything larger that 1 volt will prevent the relay to close and the meter will stay at "0".