Tube Amp Archive

For the jack, get S1029 shoulder washer and S1028 insulating washer. Tubesandmore have a good diagram on how to stack them up in the panel, and you can get them there too. Thanks. I'll finish up a list and place an order tomorrow. It'll probably be a month before I get back to this. Got to go work ...

Ok your board is a 1998 Rev. C, which is on page 10-11 of the "blues junior service manual" you can score on the 'net. Few interesting things: The op-amp is in a socket, which I don't think is factory work. It is also a TL082 vs. the called out TL072. That's not necessarily wrong. Back in the day, ...

Pictures of the reverb part of the circuit as requested.

Pictures of the reverb part of the circuit as requested.

If you have clip leads and another amp then pump the signal from the send rca into that other amp, does that amp hum? Just to make sure I understand this setup correctly.... Can I take the send RCA and plug it into the send of amp 2..... Turn both amps on, turn up the reverb and see if amp 2 hums? ...

You should not short the send cable nor did I say to do that. However if you read any DC voltage out of the send cable then that IC chip has a problem. Sorry, I got yours and Nuke's posts mixed up. When I short the Return cable, I get a much louder hum, but it does go away with the reverb knob turn...

Ok, I shorted the RCA cables as directed. As predicted there was no noise. Checked the voltages on the IC pins (4 and 8 ).... One read 15.01VDC and the other was 15.00VDC. I did not see any AC using AC or mV settings on my Fluke 117. OK, the problem is not the electronics on the board. We're down t...

Thanks! I was just realizing today that I thought I might be hearing both and it was confusing me. The 60hz is pretty quiet and is present when the reverb is turned down. I could still hear it when the reverb was turned up. I think that was screwing me up because I wasn't picking both out. Cool tric...

Here is a video of the hum.

Can someone verify if it is 60hz or 120hz?

https://youtube.com/shorts/EPHGWbICn-s? ... ROZcLA0c9_

Ok, I shorted the RCA cables as directed. As predicted there was no noise.
Checked the voltages on the IC pins (4 and 8 ).... One read 15.01VDC and the other was 15.00VDC.
I did not see any AC using AC or mV settings on my Fluke 117.

I do have a the correct tank. Got a different project to work today, but will check these items.

I ordered probes and a signal generator so I can use the Tektronics 485 I have.

Well, there was a problem with the cables. Reverb stopped working..... Removed, stripped and reinstalled, reverb works. Hum seems worse, re-did what I just did. No change. There is a pronounced sound in the background of this hum.... Almost like a cap charging and discharging maybe? Again, only with...

martin manning wrote: ↑Sat Mar 29, 2025 3:48 pm Did you try flipping the tank end-for end? The return transducer can pick up 60Hz hum if it's close to the power transformer.

Yes, I did. It surprisingly didn't change.

So, I got a good deal on a USA made Blues Junior that wasn't working. I got most of this amp sorted out. New reverb tank, killed some noise due to cracked solder joints, new switchcraft input jack, hooked up the speaker wire. Now the only thing I have left is some hum when I turn up the reverb. I've...