Tube Amp Archive

I had "The Twin" that had a severe hum issue that I fought for while. Finally one day I noticed that the Hum would change as I pushed the buttons on the foot switch. It turned out to be grounds on the Power board where IC101 is located. The foot switch/switching uses 38VAC and IC101 is a comparator ...

I have a Blues Jr. that I did almost all the BillM tweaks to it and I also replace the output transformer and speaker. The amp now sounds pretty good, before it had a crappy bottom end and I feel that the Allenamp output transformer helped a bit. I did another Blues JR. for a friend with the BillM t...

On the reverb noise, I have two of these amps that are in head cabinets. I replaced the discrete wires leading up to the reverb knob with a shielded cable connected directly to reverb pot. I cut the now unused copper patterns on the board right at the pot so they would not act as antennas. Helped qu...

R101 is 8.2 meg on both Red knobs I have, as it shows in the schematic. C117 may not be installed on your amp, my older amp had it,the newer one didn't.. I wound up adding it to the newer amp that didn't have one installed.

That is really good information.. A week ago or so I just repaired and cleaned up a ragged out 1966 Viba-Champ for a friend. I really liked it after playing on it (you have to test it after you get it going ..). So if I run into an opportunity with Fender 25R, I may do the conversion also.

Thanks Drew, that clears it up for me. Now I just have to figure the best way to place the extra resistors and cap on a the power board so it will be relatively neat and reliable.

Thanks again.

Looking good!

That is what I see in the schematic, I suspect 90ma a little more than needed on the Silver faced Twins. Then subtract the load from the preamp tubes ..
Thanks for the response...

I acquired a Red Knob Twin chassis with no tubes, cabinet,etc... I have been recapping and doing most of the mods suggested by Zenrelic in his Red knob thread. So far, so good, no magic smoke escaped and it seems to be working pretty good. The Red knob "The Twin" has a 4H 50MA choke (P/N 022707), mo...

Thanks for posting the Mods, it saved me a ton of time and trial and error head aches. I'm working thru most of your recommendations at this time. I have all my heater wires replaced and twisted up neatly above the tubes.. I have a a question about your heater elevator mod. I'm a little confused you...