I recently acquired a C4, and have been going through it slowly recapping it and replacing the VD1212 with two 4148 diodes in series. Everything works well and sounds great, EXCEPT when the tone bypass switch is depressed. When I depress the bypass switch, the sound changes radically (very bass heavy), and then about 20 seconds later the preamp shuts down. All the lights go out, and no sound. If I turn it off, and reset the tone bypass switch, all is well. This is a real head-scratcher for me. Any help would be appreciated!
Mark
Mark