Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: timmyjoe on February 16, 2022, 09:05:25 pm

Title: 5E3 Squeal with Volume Interaction
Post by: timmyjoe on February 16, 2022, 09:05:25 pm

Finished a basic 5E3 and found a problem with the interactive volumes. When plugged into the normal channel I can't turn up the bright channel past 9 without noise and then loud squeal coming in. When plugged into the bright channel the normal volume effects things in the normal 5E3 way.

Pulled and replaced just about everything in the bright channel except resistors. Not sure what to try next.

The only odd thing I did with this was to put shielded cable in some spots and also used a brass plate behind the pots and input jacks. Tried to follow this example for grounding.

Title: Re: 5E3 Squeal with Volume Interaction
Post by: pdf64 on February 17, 2022, 04:28:37 am

What exactly is meant by ‘noise’, eg hiss hum, buzz?
A video / sound clip demoing the issue may be beneficial.

Title: Re: 5E3 Squeal with Volume Interaction
Post by: timmyjoe on February 17, 2022, 08:28:06 am

Here's a sound clip.

Title: Re: 5E3 Squeal with Volume Interaction
Post by: pdf64 on February 17, 2022, 10:55:13 am

Ok, it’s definitely oscillating!
Photos of the build, especially showing overall layout and preamp lead dress, would be useful. As good a resolution and focus as you can achieve; we need to be able to zoom in and get detail, not mush.

Title: Re: 5E3 Squeal with Volume Interaction
Post by: timmyjoe on February 17, 2022, 01:27:48 pm

Thanks PDF

Title: Re: 5E3 Squeal with Volume Interaction
Post by: timmyjoe on February 19, 2022, 09:38:38 pm

Found the problem. One of the joints near the 68k resisters was not great when looking at it under magnified glass. Redid that joint and touch up all the other joints in that area. Good to go now.

Thanks PDF. Had folks over last night and it was ripping it up.