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When Good RD50s Go Bad...

Lent a buddy my '82 blonde 110 RD50 on Sunday for an all day jam session I hosted locally. You can read about the amp here:


About an hour in, the amp stopped working. It remained powered on, but no sound that we could hear.

After the jam, on closer inspection at home, I found the following:

* Reverb control acting as Master Volume (but volume is extremely low with much hum)
* Clean and Limiter side controls work but just barely discernible, and only when Reverb control turned up
* Bright and Clean/Limiter toggles work
* Eliminated tubes, speaker, speaker cable, footswitch and reverb tank as culprits

Starting checking for continuity and bad components with my audio probe, signal is passing in preamp section except lower volume when compared to my "good" RD 50. Also weak and distorted coming out of R26.

Swapped all ICs with known good, no change.

First guess is that either the signal is not getting to the power amplification section (bad resistor or cap) or something is wrong coming out of the power section.

Plan to test voltages tonight.

If anyone has experienced this type of failure appreciate any insight.



Checking voltages, found a very low reading on C43 despite correct voltage coming out of D11 to which it is connected. Cap measured correct capacitance, diode measured good. Checked continuity between them - and found none.

Either the trace under the board between these components broke or the pad for C43 (which I replaced) lifted. A small piece of wire connected to each component's appropriate lead soldered in place did the trick,

Considered pulling the board to rebuild the trace on the back side, but figured I might cause more damage in doing so.

mm210's picture

I've had to jumper several

I've had to jumper several traces on cheap pedals when the trace goes bye bye. Cheap stuff is cheap. This sounds just like age caught up to it! Those traces back then WERE a lot stronger than they are now! Mike.


Only thing I can figure...

...is that I weakened/damaged the pad and/or trace the cap solders to when I recapped the amp some months ago. I used it for an outdoor gig in November and it performed flawlessly for nearly six hours!

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