Hello all,
I have a '78 12-65-RP that was brought to me by a friend. It was sitting in storage for many years because of a reverb problem.
I repaired the reverb issue and tested the amp out. It was acting strange, going from clean to distorted seemingly on its own and all the pots were scratchy. At this point I recapped with all new electrolytic's, replaces the 16v and bias diodes, cleaned all the pots and jacks, cleaned the tube sockets, removed the "death cap" and corrected the power/fuse/switch wiring, biased the output transistors, and roled the 1458s through the different sockets, and rolled a new 1458 in all sockets, tested all resistors in place for open/shorts.
I am now left with a very weak first gain stage. I have plenty of gain if i use the mvolt input, but not if i use the High or low gain jack. Using the input jacks, the output is just a little louder then the acoustic volume of the electric guitar, with both gain and volume on 10! What am I missing?
Forgot to mention that my +
Forgot to mention that my +-16v rail is still fluctuating even after the recap and diode replacement. It fluctuates about 1.5v.
Picture
Here are some pictures of what I have done, and the original. Still trying to work out what's causing the issue. All my voltages seem to be with in the ranges that I have found on this forum. I am also getting distortion on the input if I put my signal gen on the inputs of the first 2 opamps.
112-RP-65 https://imgur.com/a/1a8Wio7
I’m in the same boat, but it
I’m in the same boat, but it is only channel 2 of a 74 130 HD. I’ve done all electrolytics and even replaced opamps 3&4. Stumped.
yeah, I am about to rip the
yeah, I am about to rip the amp apart on component at a time!
Capacitors?
Is it a bad capacitor somewhere? Luthier Vandross had success changing a .1mfd capacitor near IC-3. From the look of your picture, those capacitors look pretty new... Just wanted to chime in with an idea and wish you good luck!
Capacitors?
Is it a bad capacitor somewhere? Luthier Vandross had success changing a .1mfd capacitor near IC-3. From the look of your picture, those capacitors look pretty new... Just wanted to chime in with an idea and wish you good luck!
Thanks!
Thanks!