Vox AC30 wild buzzing

[Mars Amp Repair]

well, I have this Vox AC30/?? (not sure of the suffix). you remove the back & the board is right there like the Deville...it has 6ea 12ax7's & 4ea EL84's.

At different positions on the vol & gain pots, it buzzes. I found that redressing the filiament wires & hot glueing them in very strategic positions will pretty much cure the issue.
This sounds like the classic need to DC offset the filiament voltage. This is a Centertapped winding with the centertap grounded.
I have seen where a simple divider from the B+ can be inserted to the centertap to accomplish this.
Has anyone had this issue with this amp & is that what you did? thanx, glen

[Bruce / Mission Amps]

Find the last filtered node of the B+ rail and pull two resistors in series to ground from that cap...
A 220K and a 22K which is the grounded one.
Put a 22uF@50v E-cap across the 22K.
Take the well filtered B+ of about 1/10 of the last B+ node over to your filament supply ceneter tap lead instead of grounding it.

[Mars Amp Repair]

Thanx Bruce,
I knew I saw that somewhere....sure weird how the amp behaves when the filiament starts acting like an antenna...glen

[Peter Clothier]

well, I have this Vox AC30/?? (not sure of the suffix). you remove the back & the board is right there like the Deville...it has 6ea 12ax7's & 4ea EL84's.

Hmmmm... They usually have 5ea 12AX7's and an ECC82 for the modulator?

Peter.