Tube Amp Archive

Larry, I mean I disconnected it and your assumption is correct. The resistors are board mounted with short wires running to their pins on the sockets. passfan, I used what I had on hand for the cathode resistor. It was 2 100r 5w in parallel, but in my attempt to cool the bias a bit, I replaced one w...

No luck, replaced 120s with 1ks and the same thing happens. Something interesting is happening now though... I lifted the wire bringing voltage to the screen on one tube on the bad leg. I ran the amp with no signal and monitored the voltage at the grids, of which there was none. Then I replaced the ...

Value is 120r. I did check it when B+ was off and it was correct. Is it possible that those are drifting? I'll try to find some replacements.

It's a stable build but I recently changed out the power transformer (I was worried about the previous one's ability to supply adequate current since it used to be a two-bottle rocket). It worked fine for a short period after the swap but now this is happening. I do not suspect the PT but I can't ex...

I'm stumped. As the subject reads, only one leg glows and it happens gradually over about 5 mins after B+ is switched on. It's not the coupling cap and it's not the grid-leak resistor, those have been checked /replaced and the problem persists. I have swapped tubes as well, only the tubes connected ...

It's good to see non-board mount pots though, those are actually a more common cause of cold joints than tube sockets, despite being bolted to the chassis.

Looks good, definitely cleaner than a lot pcbs I've worked on. There seems to be a convention that just about all manufacturers of pcb amps use that can be problematic however. The preamp tube sockets appear to be mounted directly to the board. Excessive heat is not really a problem with preamp tube...

Thank you for the replies! I think I'll put this on hold then. My local tech said It would probably be fine but I don't feel comfortable taking the chance now. The transformer in question is an 18-watt style from triodestore which I have been powering my 2-bottle rocket with (which I've put 100+ hou...

Hi Tone Lover, I'm curious about why you increased the value of your first-stage coupling cap if you think the amp is too bassy? That would be where i would start for bass attenuation. I might also recommend trying smaller caps to and from you phase inverter. @MFowler, that's interesting about your ...

Can I run a rocket on 120ma or am I going to fry my PT?

The easiest thing I could do was simply try a different speaker with the same amp and guitar. It sounded normal... plus the buzzing just sounds like it's being generated at the speaker locally to my ears. It can't be anything close by rattling or the cabinet because I've held the speaker in my hand ...

hmmm... I'm not feeling or hearing any friction when I press down on the cone. The full guitar signal is still coming through beautifully but the buzzing seems to have been added to it. Is there anything else it could be?

Hey folks, It seems I may have driven my new Celestion blue a little too hard and now there's a buzzing sound whenever I play through it. I'm sure the voice coil must be warped, I've checked the cone for tears and debris that could be causing noise but it's clean. I'm considering removing the dust c...

I feel a tad foolish, but I found the problem and to my utter relief, it was a quick fix. On the rectifier board, the small electrolytic cap had come loose from it's solder joint. Thanks all you guys for your info, I appreciate it greatly!

I brought my Bassman head back from a gig about a month ago and shelved it, since I had bought a new amp that was more suitable for what I've been playing. I plugged it in the other day and I've got a weird buzzing sound when it comes off standby and if I try to play through it, it blows a fuse. Any...