Tube Amp Archive

Well now the hum went away again after lifting one leg of two capacitors, the 22nF over the plate resistor and the 1nF over the cathode resistor. I hope I found the culprit in these bizarre bandpass filters. I was able to put a 12AX7 in V1 and turn the gain all the way up without oscillation in the ...

I will take all that into consideration when I poke around in the amp again in the next day or so.

It may be a design flaw but I find it interesting that it didn’t hum until the previous tech replaced the input jack, supposedly.

Very interesting amp.

I worked on one of these Rivera-era Super Champs and I have to say it was one of the coolest little combo amps I’ve ever played. I regret not buying it from the owner. I think I would even take one over the classic Princeton Reverb, it’s just more versatile. It’s really more of a PR (2x 6V6 power) b...

I checked those points and the resistances indeed read about 0. The area I was talking about before when I said the hum went away if I touched pin 6 of V2 or pin 1 of V3, that’s this area of the schematic so I checked all the plate and grid resistors and even removed the 22nF cap and tested it and e...

Didn’t realize I can attach them through the forum itself so here they are:

Guys I have been trying to my wits end to post a picture of the front of the amp but I cannot locate the link ending in JPG to embed a photo here from my Imgur account, whether from the app or the browser. I don’t know how I got it to work for the other three pics but I will post it as soon as I can...

All voltages were referenced to chassis ground.

Yes I had a feeling some of these voltages were pretty warm on the preamp tubes.

I was just coming back on here to mention that I recall reading somewhere that Mesa did some odd things in their early amps like soldering random pieces of wire to act as antennas to curb instability so I tried that and it made no difference again unless I touched them with insulated tools, so I sta...

While probing to see if pinout voltages were normal I found that if I put my probe on pin 6 of V2 or pin 1 of V3 the hum disappears. Unfortunately the schematic that I have been using doesn’t appear to be for this amp anymore so I am back to square one on that so I couldn’t tell you what V2 or V3 ar...

Well I messed around with the amp and after the customer stated the hum didn’t appear until the input jack was replaced. A Switchcraft jack was installed and it appears this amp uses Cliff style jacks. After removing the jack from the chassis the hum on the clean channel went away. However I had a d...

That’s awesome. Not everyday do you see a Matamp clone. They are really cool amps for sure with a unique tone.

uggh. Good luck with that. I think divide and conquer is in order, starting with the easy stuff. Does the volume/tone/master have control over the buzz? Swap some pre-amp tubes and see if you get lucky. Looks like a headache to work on. I will double-check if the controls had any effect on the hum ...

Here are the only pics I have of it so far, along with what I believe to be the schematic (minus power section). Unfortunately I forgot to take a picture of the outside front before I took the amp apart: https://i.imgur.com/znX38nW.jpeg https://i.imgur.com/Q39O5sE.jpeg https://i.imgur.com/uAjjA22.jp...

Hello everyone, I’m working on an interesting amp. It’s a Kitty Hawk Junior. Some research says it is a copy of or based off a Mesa Mark 1? There is buzzing/hum on the clean channel only and I am trying to diagnose. I ruled out filter caps because it’s only on the clean channel and somebody already ...

for simplicity’s sake I just hardwired a 1M to ground simulating a master volume on 10 when the clean channel is active. Like an old Fender, I just need one volume for clean. Then the crunch channel inherits the stock master volume. good idea! there are some dual concentric 1ma pot available though...