Squealing Lang PEQ-2 - UPDATE

[sircletus]

Just got a hold of a Lang PEQ-2 that was advertised as being in perfect working order but...it's not.  Squealing and squawking, bursts of noise (via Soundcloud link below).  This doesn't have the more sporadic squealing, but gives one an idea of what it's doing.  Oh, I had a mic set up, so there's some other clanking noise in the background.

I've been wanting one of these for years, and finally found one at a (sort of) reasonable price.  If I'm looking a simple fix (replace original filter cap, which is still in there, for example), I'm going to keep it.  If this is a "rebuild the entire amp card" then I might have to send it back. I just don't have the time to tinker like I used to.

https://soundcloud.com/user-7226859/lang-noise/s-Ip3W43s6ceG

Random final question: can a failing neon lamp (the power indicator looks like it's on its way out) dump garbage into the circuit?

 

[mjrippe]

Have you removed the tubes and cleaned tube pins and socket contacts?  Do any of the controls change the type/severity of the noise?

 

[sircletus]

Have you removed the tubes and cleaned tube pins and socket contacts?  Do any of the controls change the type/severity of the noise?

The PEQ-2 is solid state, so...no.  ;D

 

[Ricardus]

We're got one of those at our analog room and that one needs some looking after also.

 

[sircletus]

We're got one of those at our analog room and that one needs some looking after also.

What's yours doing?  I left mine on for about 8 hours today and after about an hour the noise seems to have disappeared.  Go figure.

The circuit is simple, but I don't exactly want to rebuild the whole thing after dropping a hefty chunk of dough on it.  At the very least I'll probably re-cap the power supply and test diodes and transistors.  But as I said in the original post, I'm not sure I want to put the time into it after having spent the money.

 

[Ricardus]

What's yours doing? 

It's just not passing signal. I haven't had it in front of me in at least a year. Next time I see it I'll open it up.

 

[mjrippe]

The PEQ-2 is solid state, so...no.  ;D

Hahaha!  Obviously I'm only familiar with the early models 

 

[sircletus]

Hahaha!  Obviously I'm only familiar with the early models 

No worries.  The problem actually stopped for some reason.  Now it's fine.  I'm going to go ahead and all electrolytics anyway.  I think there's only 5 or 6 total between the power supply and amp cards.

 

[sircletus]

Did a full re-cap (all of 5 caps) and it's been just fine.  But I thought I'd share photos of what I found when  I pulled the power supply card and the amp card: some shoddy repair work!

 

[sircletus]

And another!

 

[emrr]

Yes old neon can dump all kinds of crap into circuits, even turn into an oscillator.  It might have moved off of critical frequency, might come back. 

Every now and then I see an old amp lacking power ground that also squeals until case grounded. 

 

[sircletus]

Yes old neon can dump all kinds of crap into circuits, even turn into an oscillator.  It might have moved off of critical frequency, might come back. 

Every now and then I see an old amp lacking power ground that also squeals until case grounded.

Very interesting, Doug, appreciate the insight!  Replacing the old neon will be the next quest.