The Amp Garage

Cool thanks guys

What a nightmare dissasembly ;) Repaired one of these last week, came in with burnt R61, R62, which are (2) 22r is parallel in the neg voltage supply. Also, U1 , the 4558 , was cracked, which is fed by the neg voltage. lucky it is socketed. Repair seemed straightforward, I replaced the 4558 and 22r ...

Ok thanks guys. The F30 is fine for now The Rocket 44 is another story. I actually had the luxury of having 2 in at the same time. It has the same silly dynawatt arrangement with the neg V supplies and PI setup as the F30. This one hummed pretty badly even with good tubes/bias and new caps. The PT w...

Have had 2 of these on the bench today, first the F30. I was able to drop the 120K dropping resistor in the neg voltage supply down to 100k, and got some JJ el84s right at 21ma. Of course the problem is that the same neg V feed also feeds the PI cathode negative voltage, which needs to be at 3V (per...

Stock MM 5e3 power transformers produce 400VDC+ , so that's likely what's going on here (looking at the website description) . They likely had some tweedle dee stickers printed up

That would certainly take it in the right direction. It’d be interesting to hear from someone who has built a Tweedle to the spec published here on TAG. Hey Martin, I built one 10 years ago or so (I think it was a Triode Kit!) , I remember it being a great sounding amp, but basically just a tighter...

Ok thanks all. The last 2 filters ground at the input jack, and I had a compromised connection to chassis there. I hit it w a dremel and its stable, which is what I should have started w this morning ;( But isn't it slightly terrifying that if that connection to chassis gets lost, at the input jack,...

Hey Steve, thanks, I think you may have omitted the "first" problem in your response. Also, thanks for pointing the voltage situation out. I was in "spongy" mode so plates were only 390, and only 10V was being dropped across the whole rail (with ALL tubes in). Nonetheless, I've now realized that eve...

And yep, there is shielded wire at the grid, that was one of the first things I did was pull of the shield ground, it's connected to the ground side of the 47K under the cathode cap

No doubt it's mechanical, but for HV to be everywhere is special
I though a shorted coupling cap off the plate could be a possibility.

Not seeing any arcing, but that is my fear that arcing occured and traces are shorted. I guess I'll pull the Rp and see what happens

This one has 380VDC at the input jack, which is the supply voltage for V1. Even with V1 pulled (or replaced), I have 380V at the grid, at the plate, at the cathode at V1. The input jack is metal switchcraft, non isolated, but chassis is painted. When I remove the input jack and float it out of the c...

Turns out this used Twin was shipped from GC in May. Worked great briefly then started developing issues until it smoked. So there's the rough handling, I assume. Once I got the board cleaned up and made sure no traces were shorted, I floated the Rk and Ck right off the socket to the 1M grid ground,...

Twin reverb reissue, with the 2k2 Rk of the reverb driver 12AT7 charred. Looks like it burned up it's cathode bypass cap also, and some other nearby components need replacing . I'm replacing the verb xformer too, as my first guess at to the problem, if not the tube itself. However, I'm scratching my...

I had the 212 configuration (Belaire) of this amp in for repair and was really impressed with it. I saw it had been modded and lo and behold there's a whole set of mods for it online from decades ago. So I found a local 112 version (Nomad) and did my own thing to it. My version which I believe is ea...

Best I can do given time, but it's all there.