Hiwatt DR103 Clone oscillating

[bxershrts]

Hello everyone,

I built a a Dr103 clone and it all works and sounds great except for the master volume oscillating between 95-100% clockwise.
The amp only oscillates when the MV pot is all the way clockwise - .

What mitigates the oscillating is with the mv FCW and the treble FCW as well.

With the mv all the way clockwise and the treble all the way clockwise the amp functions great, albeit bright and lacking just the treble control autonomy.

When I turn the treble counterclockwise (from FCW) and the MV still FCW the oscillating starts, then at which point if I turn the mv back slightly the oscillating goes away.

I built it in the same way as the originals and used vintage Mullard mustard coupling caps.

Wanting ideas on where to turn next..

Thanks!

[bxershrts]

Here is a picture of the build

[pompeiisneaks]

Generally we prefer not to double post the same content in multiple locations. If you'd prefer your original post be moved into the Vox/Hiwatt Discussion area I can do that for you.

~Phil

[bxershrts]

Thanks Phil,

Please keep the post located in The hiwatt Group and remove from the other area.

[pompeiisneaks]

Moved, are you fine with me deleting this duplicate thread?

~Phil

[bxershrts]

I am fine with you deleting it - the other members have provided some great insight and idea that may help others. Can you combine the threads?

[pompeiisneaks]

I mean, i can, but this threa dliterally just has your posts that are duplicate and yours and my interaction about this thread being duplicate.

~Phil

[rooster]

The dual pwr supply cap mounted on the side wall by the inputs - were it me - I would rotate it 90 degrees towards the back wall of the chassis. That's just asking for trouble. Too bad I can't see what others have suggested....

In the JTM45 there was a pwr supply cap mounted internally, yep, but it was on the other side of the amp. Too, I think the original DR103 layout suggests a vertical install of this cap can?

[mhuss]

No, that 16/32 cap was always mounted on the side (from 1969 or so). On the much later amps all the caps were mounted inside on the sides. https://hiwatt.org/pix.php?p=DR504_2guts The chassis are huge, so there's plenty of room.

I think I asked this in the parallel thread, but did you ground everything as per the original layout?