I would be interested to have people suggest how to go about testing them, because it is obvious that nobody is going to pay like $1k without some guarantees they work. What are people going to be looking to know? E.g., I am sure the pots and switches are going to be noisy after all these years. Is that an issue? Or is it just that sounds still comes from all four channels when fed some random stereo input? I suppose I could easily check that with some headphones. Just what would somebody need to know to pay more than a couple hundred for these decoders?
Also, I don't know of any SQ/QS digital sources that I have access to. Are there some obvious ones that I might have and not know were quad? I have ~1000 CDs spanning rock and classical, going back to the beginning of CDs. I Do still own many SQ and QS LPs, but don't have a turntable setup--all digital streaming now. Perhaps after retirement I will get around to digitzing. Right after I digitize all the film photos of my daughter, etc., etc.
Again, thanks for the input. I remember being passionate about quad back in the 70's. I see many people still are. I remember that I have a couple of Steely Dan LPs where the quad versions had alternative takes--alternative takes that I thought were much better than the standard stereo versions. That was very cool. Would love to have those to listen to now.
CD4 isn't going to be easy since it doesn't have a digital counterpart, at least not yet.
But you could do a cursory test of QS & SQ not decoding a source but by using each one's synth function on a good CD. There are some that synth quad much better than others, but what you'd be looking for is
scratchy sounds with controls
a channel dropout or much lower volume relative to the others, which may indicate a cold solder joint, pot or switch problem. The QRX-x001 receivers had problems with this, but not sure about the decoders even tho I own both!
unusual distortion type noise, unstable overall soundfield or squishy sounds that might indicate a decoder chip problem. I did have this issue with the QSD1 I bought off ebay, which was diagnosed as nearly all the chips needing replaced. My Audionics as bought had good rear left-right separation but front was center-focused with almost no left-right separation; that was diagnosed as one of the Tate chips, what he called the control chip being defective...luckily the restorer knew someone with a completely dead Audionics so I bought that person's chip so the restorer could fix it and it had worked fantastically since.
Re-capping (replacing capacitors) is something to be anticipated but what you'd be looking for other than control noise is some indication of a chip problem. My guess is if you had them stored, and they worked OK before being stored and not subjected to power surges, then the chips may be OK.
QRX Restore in Washington state can restore the Sansui for sure and possibly the Audionics if needed. But the chip supply for the QSD1 is very limited and as far as I know, replacement Tate chips for the Audionics are non-existent unless he has or can get his hands on one. I got lucky with mine
There were only about 250 Audionics S&IC made. The QSD-1's used to be quite rare to find on Ebay but for the last 2 yrs, you might find one here or there FS. Of course, the shape it's in is the issue, mine was not in good shape even tho the seller advertised it as in perfect working condition. It was not. It had a noisy background noise, not a hiss or hum but definitely a distorted sound from some of the channels.
My thought is if the synth function seems to work OK on a few CDs, then the straight decoding function may also be OK (tho not guaranteed) since the chips are used for both. It's a start anyway
