Video of the buzz issue with the AB763 new build

[Planobilly]

I hope the audio is clear enough for you to hear the issue.

Any ideas?

Thanks,

Billy

[dunner84]

Wow, that is really odd. I hope someone has some insight for you. You almost need a signal generator and an o-scope.

[whoops]

Hi,
can you post the voltages?

What AB763 circuit did you build? Hoffman, Fender, 1 channel , 2 channels, etc?

[silverfox]

I'm going to advance the "notion" it's a capacitor. Check the filter capacitors since it is most prominent on low frequencies. Could also be a cathode capacitor. Again, just a suspicion.

silverfox.

[Planobilly]

Hi guys,

In the strange world of tube amps this problem turned out to be a simple bad tube socket. I could not find the issue by the normal process of rocking or twisting the tubes around.

I had to disconnect stuff and test stage by stage to narrow down the issue to V2.

I too thought this would turn out to be a failing capacitor.

So...as of this point in time, the amp works and sounds as it was designed.

I did have a couple of other component failures that caused me some grief. Perhaps bad components, perhaps I overheated them, perhaps all this is just normal for someone who lives in the Bermuda Triangle...lol

Cheers,

Billy