Tube Amp Archive

Sure I'm aware of safety precautions, the problem is I don't know much about how transistor amps operate or how to test them. I have a light bulb limiter but I did want to measure how much current it's drawing without the limiter. I had to put it away for a minute but I will check it again and see w...

I'll check that, by no load do you mean no signal going into it? I can't leave this thing on for more than a few seconds without panicking, it's so loud and awful sounding and it definitely had a loa do it at idle pulling over 1.5A with no signal going in and controls at zero and the preamp tube rem...

I'm having a look at one of these for a friend and I really have no idea what I'm doing. I could use some tips on how to approach troubleshooting the amp. The symptom is it makes a loud horrible buzz/hum when you power it up. Problem occurs in both channels with all controls at zero and preamp tube ...

It's a JMP 2203 from the early to mid 70s I'd guess. It's pretty much stock, the inputs have been changes so they're both high gain and mixed with a pair of 68k resistors. And all the power supply can caps have been replaced with Ruby caps. There's nothing really wrong with it but I assumed that rep...

Would replacing the stock Lego caps with Sozo or other film caps like Xicon MPP, NTE or Panasonic be an improvement if you're looking for a smoother less fizzy tone?

Cool, thanks.

What if you have a pair of 100 Ohm resistors making a virtual center tap on your 6.3v winding when the power transformer has a center tapped 6.3v secondary? I replaced a transformer and the new one has a CT and I'm wondering if I need to snip those out or if there is some benefit to leaving them? Se...

Way to go tubenoob! If you're not careful, you're gonna have to change your user name! Thanks! This is fun stuff. With both the Fender and the Vox I had no idea at all where to begin or what to do and I wished that there was more feedback being thrown my way because I'm so impatient, but there was ...

I hear you, and I agree that you can dial in an ok overdrive tone with eq and presence settings but for me it kills the clean tone. I couldn't find a balance between clean and overdrive so here's what I did. First, I abandoned the idea of adding the unused triode, I got as far as cutting the traces ...

I thought maybe I could share something that might be helpful to someone. On this version of the Blues deluxe there is no boas adjust pot and no bias test point. I followed the trace from the power tubes cathode and found that on the main board there is a jumper wire maked Wxx that is a perfect spot...

After messing with this thing all day I got it working. There's a .1 1000v cap called R51 on the board right around the power supply area that had a cold or broken solder, it was causing the problems I think, cause when I wiggled it all he'll broke loose and when I retouched it with solder everythin...

The heaters are definitely on when it fades out, the filaments are glowing and there is voltage everywhere there's supposed to be.
I have the board pulled at the moment...don't really know what to do but I'm looking at it.

... Are the output tube heaters going out when the amp fades off? It would also I seem at this point test it's time to pull all the boards out ( yup that main board is a pain) and check all the solder connections! Also just for kicks jump the standby switch and see if that cures the fade out. In re...

Weird thing, I tried another amp's preamp out to the Fender's power amp in and it worked! But then it slowly got more distorted, with hard picking it was distorted then after a minute or so it faded out and no signal. I measure all the plate voltages of the power amp and preamp and the all seemed no...

Does anybody know hot to adjust the bias on these amps? There doesn't appear to be a bias pot, I see a 27k resistor, R87 on the schematic, do I need to change this value? How would I replace that with a trimmer?
Anybody? Help...