Forte 1a left channel buzz

[Les Berkley]

I have used my Forte 1a for at least twenty years now, and it has been exemplary. Recently it developed a buzz in the left channel that begins after about two minutes of warmup, and doesn't go away thereafter. I have another amp in the system, and all is well, but I'd love to be able to repair the Forte!

Thanks!
Les

 

[Zen Mod]

and , the question is ?

 

[Les Berkley]

What would be the basic diagnostic procedure to determine the cause of the buzz?

 

[jacco vermeulen]

Lytic can oil-exchange.

 

[Zen Mod]

or just oil-in-can exchange ?

 

[Andersonix]

If it's a weak PS cap and a single PS for a stereo amp, why is only one channel buzzing?

 

[Zen Mod]

it's time for overall electrolytic caps change

you're having some caps on pcbs , too

 

[jacco vermeulen]

buzzing?

The Model 1A doesn't have a single PS, has a bridge rectifier and two cans for each channel.

(Model 3 has a "single" PS, power supply of the 1A, but piggy-back cans)

Papa no need no helper slaves, only small foilies and a stnkg big SideReal.

 

[Les Berkley]

So the first thing to try is the electrolytics? I assume original replacements are unavailable, but are there good current options?

 

[Zen Mod]

just to be sure that your specimen is intact ( ref factory ) , it's good to have some pics posted

sorry - I'm thinking better when aided visually



( after dozen of years of constant service , it's not unusual to have dying caps)

 

[jacco vermeulen]

good current options?

Digikey, try Cornell Dubilier (CDE)

In that uF size, with screw terminals, likely have to pick 50Vdc ones.
Go for CGS types (Computer Grade special, Screw me)
They're actually the same Mallory CGS's, which Poah used in his Dark&Hairy days.

 

[Les Berkley]

Will post some pictures tomorrow.

 

[HWM]

Hi,
I know I'm waaay late to this party, but I too have a Forte (Model 3) that I've replaced the PS caps and the 2 yellow film caps. That's all. It was dead quiet before the change, now there's a slight buzz on the left channel. I'm not a pro, but did check solder points and everthing seems solid. I can't figure out why it's buzzing? It also buzzes without any inputs hooked up, so it shouldn't be a ground loop issue. As I noted, the buzz is barely there and the amp sounds great, but it's driving me nuts. Any insights? Thanks.