The Amp Garage

,,, I actually ended up raising my Bridge Pickup so its 2/16" from the strings (unfretted) as I found out it was very low compared to Gibson's Standard Spec which is 1/16" when the strings are held down at the 22nd Fret. Hard to describe how the sound has changed, definitely got more bite which is ...

An electronic DVM will give nonsense readings on floating voltages such as you would have with unconnected windings, or on any winding to ground with the transformer out of circuit. (If you got these voltages with a moving coil meter, then the transformer probably has problems.) Figure out which wir...

badoumba wrote:...is there any reason for not going for a power tranformerless option?

Yes: Safety.

Don't do it.

gui_tarzan wrote:And if you're welding overhead, don't wear a belt or button your shirt cuffs.

And cover your ears!!

p.s. - I've been informed that this is called the tri-oil method :) Could that be 'Tru-Oil' method? It's very similar to the recommendations for applying Brichwood Casey Tru-Oil gun stock finish (I think it's a varnish rather than an oil, though and is often used for guitars). https://www.birchwood...

stephenl wrote:The screens are fed from a mosfet amplified zener stabilizer...could that be inducing the noise?

*Could*, yes - do you see any oscillations on the screen supply?

Are the screen resistors on the socket, too?

stephenl wrote: I have 10k grid stoppers soldered directly to the socket grid pins.

How about the screen resistors?

If it's quiet as you describe, then the grounds are good. It could be noise from V2 heaters leaking in or the lead between volume pot wiper and V2a grid picking something up (maybe from the heater lead, a you suspect). You could try an artificial centre tap (fit 2 x 100R resistors across the heater ...

Glad to hear you're getting there!

Littlewyan wrote:O btw the issue with the volume going quiet when on full only happens when all tone knobs are turned to 0 so I guess thats normal. Doh!

Doh! indeed - I should have spotted that...

Edit: Do you think its worth connecting the 40x20x20x20 to the back of the pots and leaving the 50x50 by itself? FWIW, I'd connect the 40/20/20/20 to the chassis where you have it now, but run the -ve of the 50/50 (40/40?) to the -ve of the 40/20/20/20 (as I described above), rather than direct to ...

Right an update. I move the HT CT to the cap can negative terminal but it didn't make a difference. Hmm.... That's a shame! :( I can't help but think that this still has something to do with it.... If you had the stomach for it, try the CT to the -ve on the 40/40uF can, but remove the ground wire b...

Littlewyan wrote:Right an update. I move the HT CT to the cap can negative terminal but it didn't make a difference.

Hmm.... That's a shame!

Ill undo the ht ct and use a test lead to connect it to the 50x50 cap negative terminal to see what happens. FWIW, I would suggest a short, direct, heavy gauge wire for this connection, as it has high current pulses on it which could transmit noise into the preamp - my image of 'test lead' is of so...

What are the wires with crimps on at the 'top' of the power supply board [1]? Is one of them the power transformer centre tap? I think you have two separate problems: 1) The 'going quiet' is likely oscillation as Glenn has suggested - likely to be a lead dress issue around the preamp. 2) The buzz:- ...