Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: Planobilly on December 26, 2016, 11:42:40 am

Title: Video of the buzz issue with the AB763 new build
Post by: Planobilly on December 26, 2016, 11:42:40 am

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

Any ideas?

Thanks,

Billy

Title: Re: Video of the buzz issue with the AB763 new build
Post by: dunner84 on December 26, 2016, 05:27:42 pm

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

Title: Re: Video of the buzz issue with the AB763 new build
Post by: whoops on December 26, 2016, 09:09:01 pm

Hi,
can you post the voltages?

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

Title: Re: Video of the buzz issue with the AB763 new build
Post by: silverfox on December 27, 2016, 01:28:09 pm

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.

Title: Re: Video of the buzz issue with the AB763 new build (FINALLY Solved)
Post by: Planobilly on December 28, 2016, 10:07:46 pm

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