Help with bizarre Wadia CD player problem

[cynix]

This is a really strange one, would be grateful for any help or advice please.

I've had this Wadia 830 CD player about 20 years, never had a problem and always had it connected via the balanced outputs to a big class A balanced power amp. Have been trying some lower powered amps lately and have now got a pair of power amps which only have phono inputs, no balanced inputs, so have been using the phono outputs on the Wadia for the first time. The problem isn't with the new power amps as I've tried this on 3 different amps now and the problem appears on all of them when not using a balanced to balanced connection.

When using the phono outputs of the Wadia (or even balanced to phono cables from the Wadia to the amp) I get a high pitched squealing sound from both speakers, even if the Wadia isn't playing a CD and is still in mute mode (relays shorting the outputs).
The balanced outputs are still fine when connected to the balanced inputs of a power amp, no strange noises and nothing overheating on the Wadia board and it sounds fine. But using phono to phono or balanced to phono leads and I get the squealing and have detected some overheating of components on the board.

Pic below. These components are mostly mirrored on the opposite side of the board, but strangely this isn't a left/right channel problem, the squealing comes from both channels on the amp even when only 1 channel is connected from the Wadia, either left or right doesn't matter, just one connection produces squealing from both speakers.

When it's squealing the 2 regulators shown are getting very hot, the left one (7812) is hitting 60 degrees and the right one (7912) is hitting 90 degrees, whereas the identical pair on opposite side of the board are only around 30 degrees. When connected via balanced to balanced cables they all sit around 30 degrees and everything sounds fine. The big capacitor at the right is also getting a bit hotter when the squealing occurs, but not nearly as much as the regulators. Nothing else I've tested seems to be overheating at all.

Any ideas please? Thanks!

 

[cynix]

Have done some more testing and found something which may or may not be OK, maybe someone with more experience could comment.

The bridge rectifier just to the left of the big left capacitor has an input of 33v AC, the output on the negative pin is -9.5v DC and the output on the positive pin is 33v DC. Does that sound OK?

The 7912 regulator gets +12v DC to its ground pin and the -9.5v DC from the rectifier to it's input pin, giving a -21.5v DC input. The 7812 regulator gets +12v DC to its ground pin and the +33v DC from the rectifier to its input pin, giving a +21v DC input. So both regulators are within their correct input range but it just seems like a strange way to do things.

The same +12v DC which goes to the ground pin of both regulators seems to also be present at the phono output grounds on rear panel, which may be the source of the problem. But the strange thing is that this +12v DC is coming directly out of the torodial transformer itself.

Or could it be the 7912 is faulty and it's injecting the +12v DC to ground?

Any thoughts?

Thanks.

 

[hifinutt]

contact Tony at coherant audio . he knows almost everything about wadia !! he is always helpful

https://coherent-systems.co.uk/

 

[rabski]

It definitely needs looking at. Ground should be exactly that: 0 volts referenced to the circuit. Anything more than a couple of mV of DC on signal grounds is serious cause for concern. There should be no DC content on either the signal ground or the signal line.

The symptoms look all over the place and it could be something absolutely simple like a ground wire broken somewhere, allowing things to 'float'. On the other hand, it could be something definitely non-simple.

 

[cynix]

Thanks guys.

I've removed both overheating regulators and the ground output is now down to 1.2mv and the rectifier output is at -21v and +21v rather than -9v and +33v, all of which seems a lot more reasonable. And no whining when plugged into an amp via phono outputs. I didn't try playing a CD as only one half of the board is properly powered, but so far it's a big improvement.

Will order a new pair of regulators and see how it goes with those fitted.

Thanks.

 

[cynix]

Hmm well not really any progress unfortunately. I replaced both regulators, no change. Replaced the bridge rectifier, no change. Removed the big smoothing caps, still no change. So it seems whatever is creating the ground problem is causing the regulators to overheat but not actually overheating itself, which is strange.

So I think I'm close to the limit of what I'm able to diagnose myself, does anyone know someone who could take a look at it near Glasgow? I really don't want to have to post it anywhere as I know how fragile (and impossible to replace) the CD mechanism and laser are. I've mailed coherent audio to see if they can suggest anything.

Best option may even be to try finding another one and just keep this one as spares for the CD mechanism and laser as they're still working fine. Anyone have an 830 they'd consider selling?