Blues Hound wrote:
I put 100 ohm resistors on V5 going from Pin 2 and Pin 7 to ground, just like Francesca...
It should help with the 60 cycle hum.
Easier, since this has Moose's transformers, would be to tie the filament centre-tap (brown with white trace) to ground, which I can't see having been done in the pictures. I can see the wire is there in an early picture but it's not tied to the common ground point.
That's almost certainly the cause of the 60Hz hum.
paulster wrote: ... tie the filament centre-tap (brown with white trace) to ground...
Paul is right. The 100 R resistors Ken used in Francesca were a "virtual" center tap, used because there was no center tap in the filament circuit of his PT.
There is a Star ground right under the IEC connector that the mains ground, bias board ground, and OT center tap all go to.
This is according to the Ceriatone layout.
The 60 cycle hum I have is definitly from outside sources. If I block the open chassis with something metal it goes away...and if I put my hand inside the chassis while powered (being careful of voltages of course), I physically increase the 60 cycle hum.
Right now the only issue I have (besides finding tubes I like and dialing in the tone), is the hiss.
Lonely Raven wrote: There is a Star ground right under the IEC connector that the mains ground, bias board ground, and OT center tap all go to.... If I block the open chassis with something metal it goes away
I'm sure you mean PT center tap to the star ground. The OT center tap goes to B1+. Sounds like you just need that bottom cover on the chassis to cure the hum problem.
Lonely Raven wrote: There is a Star ground right under the IEC connector that the mains ground, bias board ground, and OT center tap all go to.... If I block the open chassis with something metal it goes away
I'm sure you mean PT center tap to the star ground. The OT center tap goes to B1+. Sounds like you just need that bottom cover on the chassis to cure the hum problem.
Ahh, your right! Pre-Coffee post and being on 24 call and wakened at 3AM doesn't help much.
After finally getting to crank the amp the other day, I'm confident in my build. I just need to dial her in and tame this hiss.
I do so wish I could put a PPIMV without ruining the TW design. I'm looking at building an Airbrake next and considering some Scumback Greenback style speakers on Glens recommendation. I've already had a chit chat with Jim about a pair of those speakers....I just can't afford any of this right now...I need to start buying for others this holiday season!
