Stereo Receiver Trouble Shooting...

[manxam]

First of all, Happy New Years!

Now on to my question. I have an old (80's) Aurex (Toshiba) SA-5000 reciever in which the left channel randomly cuts out while using any of the inputs on the back.

I've tried various sources and inputs (aux, tape, tape2) but to no avail. The amplifier stage seems to work correctly as the audio never cuts out on radio or when in mono mode.

I've scoured the board looking for bad solder joints or any tell tale sign that something is faulty but have found nothing.

Where should I start looking or what/how do I test the different components to diagnose the problem?

This receiver sounds better (IMO) than my old NAD 3140 and Onkyo HT unit and I'd really like to fix it.

Any help would be greatly appreciated.

Thanks!

 

[Netlist]

I don't know the receiver but are the input selection buttons all seperate or is the tuner and aux the same switch? Is there a tape/source switch, etc...?

/Hugo

 

[manxam]

All input selections are on the same switch (tuner, phono, aux).

There is also a tape switch with which you can select: source, tape1, or tape2.

I've tried using the tape and aux inputs but the problem is the same.

Thanks!

 

[Richard C]

The problem seems to be located in a relatively small area: external-input circuitry BEFORE the mono switch.

Most likely electro/mechanical (switch or connector) rather than electronic. Check the obvious, I wouldn't expect intermittent sound to be due to electronic component failure. Check signal path continuity with a meter or scope.

If you don't have an oscilloscope you could use the working channel as a signal tracer. Make a probe using a 100k resistor in series with a 100n capacitor and connect this to the working channel. WIth the volume set low feed a signal into the faulty channel and use the probe to listen for the break.

 

[Netlist]

Yes, this needs a follow-the-trace approach.
It could be the mono switch.

/Hugo

 

[manxam]

Thanks for the responses and suggestions. I'll crack into it again tomorrow and let you know what I find, if anything.

Thanks!

 

[manxam]

Well, that ended in bitter failure.

It's far too difficult to trace the input path for this particular amp.

I'm totally lost now. If only I could find a schematic for this receiver I'm sure i'd be ok.

Would a digital picture of the internals help one of you guys out w/ suggestions?

Thanks for all the help thus far

Cheers!