Tube Amp Archive

Thanks for the responses! I appreciate for the reassurances about the 5U4 - I did some math and it looked to me as though the OT was pretty stressed with a 5Y3, and the 5U4 would be too much current, period....if that's not the case, that's a relief. I will pull the tube & test & then check the othe...

Just opened up a SF Vibro Champ which has very little output and odd behavior on the Speed and Intensity controls. Speed doesn't have appreciable effect, and Intensity acts like it's a gain stage. As far as I can see from matching parts to the schematic and layout (AA764), the amp hasn't been modded...