Problem with WA 88

[bob orbell]

Hi Andy, no it is still exactly the same as before the transformer swap, I have two sets of valves (KT88) and still the problem is the same, same channel. Going out to get ****ed tonight, bollocks to the thing, no I will try again tomorrow. BOB

[Phil Y]

Pub

[bikerhifinut]

Don't lose heart Bob.
You guys gave me the support to carry on when I was ready to chuck it all in with Phono3/PSU3 and the CF.
I reckon it sounds a bit like an electrolytic packing in, assuming that you use plastic coupling caps.
I'd swop out all the cathode bypasses, just use decent "cooking" variety ones and see if that works.

Touch wood I have been lucky with the WD88 amp, never missed a beat and the only probs I had were a couple of KT88's that lost their vacuum mysteriously.
And that's when I found out that Svetlana KT88 are rocking horse poo. But that's another story.

By the way, the Phono3 is still unstable, but I'll sort it.

A.

[bob orbell]

Thank's Andy, no I never give up, the problem is there, somewhere, today I will try the cathode bypass cap's, and the other two on the input tag board, if that don't work, then I will build all new boards with all new parts. BOB

[Richard]

Well a right faff no doubt but at least you've ruled out the OPTXs Bob.

How does it actually happen? Is it playing away happily then fades noticeably? Does it happen quickly, have you heard it make any other noises, clicks pops etc? Is one channel then very much lower than the other, like say half level? Yes as Andy says a bad cathode bypass electrolytic, or solder joint maybe, even a resistor going high perhaps. Unlikely with plastic film caps or Rifa electros though if you have those, even if it's a few years old they have massive lifespan.

[bob orbell]

Well gentlemen, this morning I changed C4 (220uF 16v) capacitors for new ones, it looks like they are the ECC83 cathode bypass, plus feedback, BINGO , all seams to be working fine, these were the originals, just to recap Richards question, the sound just shifted to the left very slowly over about two hours, the HF's were also lost on the right channel, well I am going to have a good long listen, this afternoon, thank's for all your support and help, nursing a badly torn thumb at the moment, had to go to the hospital, caught the thumb in my circular saw, about 11.00 o'clock, not recommended. BOB

[bikerhifinut]

Fingers Crossed Bob.

I thought it sounded like an electrolytic going off colour as it got warm/hot but you can never tell with these things.

Hope your thumb heals up soon. I did a daft thing with the soldering iron last week and took the skin off my left second fingertip. Ouch.

I'm not doing anything with my stuff until the parts arrive from Glassware Audio. I don't know how long it usually takes or if I will get stiffed for import taxes yet.

Andy.

[bob orbell]

Well, after that initial quick listen after replacing C4, I spent yesterday afternoon with it for over three hours, my hopes were short lived, no change, the sound still drifted of to the left, back onto the bench (blasted thing), I sat looking at the CD, and wondered if the HT capacitors C9 my be to blame, so this morning I swapped them over (left to right), I have now been listening for over two hours, and guess what, the sound now moves over to the right, so I think that is the problem, these too are the originals, sadly, RS don't do this value in 500 volt, so Im gona give Matthew a bell. Fingers crossed. BOB

[bikerhifinut]

Originally Posted by bob orbell

Well, after that initial quick listen after replacing C4, I spent yesterday afternoon with it for over three hours, my hopes were short lived, no change, the sound still drifted of to the left, back onto the bench (blasted thing), I sat looking at the CD, and wondered if the HT capacitors C9 my be to blame, so this morning I swapped them over (left to right), I have now been listening for over two hours, and guess what, the sound now moves over to the right, so I think that is the problem, these too are the originals, sadly, RS don't do this value in 500 volt, so Im gona give Matthew a bell. Fingers crossed. BOB

Hopefully You've nailed it bob.

What value are the caps in the WA88? HFC do 600V ones up to 100V, not cheap though and not "boutique" either.

A.

[bob orbell]

Hi Andy, they are 120uF 500v, got some coming from Matthew. BOB