Tube Amp Archive

Hi guys! So - I've replaced that 820r resistor and I now have 1.93v on pin 3, which I think is much better than 0.1-0.2v that I had before, however, the preamp is now much louder, but no more gain than before in terms of saturation! When the amp was working previously it had that nice medium/highish...

Hey Phil thanks for that I've just double checked and yes I've got a 10k where the 820 ohm one should be, so looks like its the culprit.

I'll give it a whirl tomorrow hopefully and double check everything else at the same time.

Thanks again

I was hoping it was Phil, but didn't want to assume. You guys would know much better than me. Could definitely explain why it works great but is just very clean if I'm dumping a ton of that part of the preamp stage to ground (I'm sure that's not technically correct!). But be great if that's all it i...

Although, that 820k runs to ground from the pin, so actually it might not be that (although still needs a swap!)

Hi thanks for that, it isn't shorted to ground, but you mentioning that pin and me looking had prompted me to look at the 820k resistor that is tied directly to that - I uprated a couple of resistors and just did a colour coding check and its a 10k instead of 820k, not sure how that happened!!!!! So...

I think the 24v on pins 2 and 7 shouldn't be there on v3!! and pin 1 v1 seems high?

Its been 'clean' since I redid the wiring, and was like it before I put the PPIMV in. I've checked, double and triple checked the diagrams... but can't find a wiring issue.

Thank you to everyone for your help, I actually redid the wiring for the preamp tube sockets (better twisting and used the ampwizard style of wiring to the lugs), I also redid the grounding wiring, and added a PPIMV which I think is great, and a better impedance selector switch. Hum is no longer an ...

One thing that did just dawn on me, like an idiot, is that the board I got was partially populated and I hadn’t considered they’d probably used lead solder - so if I’ve then used lead free to solder my wire to the turrets then that’s a sure fire way to get some serious dodgy joints 😟 I can’t just re...

Thanks Phil - yeah I’m definitely no pro! It is lead free, should have just used the leaded, it’s so much easier to work with too! Shame it’s not the best of things for your health! I’m going to redo the connections to v1 and ergo over the whole thing to check for bad joints - hopefully that’ll help...

The main pics didn't seem to work...
they're here:




thanks!!!

Pics (hopefully!) I pulled preamp tube 2 and it was silent (just hear the noise very very faintly), pulled tube 1 and it was silent (just the faint noise), pulled just tube 1 on its own and its still really quite with just 2 onwards. Tried swapping it out for 3 different tubes, but still the same no...

Thanks everyone for your replies! I know its a can of worms searching for the culprit (and I'll take some chassis pics tomorrow which should help - hopefully you'll see I've done something stupid and easily rectified like multiple grounds or something!!!) I have a set of Tung-Sol reissues too (I've ...

Hi everyone! I've built my first ever amp, a JCM800 50w 2204, its awesome and sounds fab, however, I do have a hum issue. I'd really really appreciate any help and experience anyone can give, its PtP wired, I'll pop some pictures up soon but wanted to get the ball rolling in case anybody had any ini...

Hi! I have a 1979 ac-30 - rose Morris but only just, if you know what I mean. It is PCB, but the one with 2 thin boards with the components set up in an accessible fashion and panel mounted pots. I got it from a friend for cheap as it needed a little work but I've rectified the actual 'issues' - new...