Strange squealing in amp when powered up.

[martin manning]

Getting back to the problem at hand (Matt J's amp), rearanging the existing rectifier board wiring is pretty easy. Get rid of the ground wire and the jumper at the anode ends of the diodes at the lower right, and move the two red wires all the way over to the right. The B+ (yellow wire) is good as-is. And of course, ground the red/yellow CT. It's possible that some or all of the power supply caps were damaged by the high voltage, so replacing them would be a good plan; same goes for the diodes. Adding a 0.01uF 1kV ceramic cap in parallel with each diode will help balance the voltage across them.

[Matt J]

Thanks Martin!

Should I just go ahead and copy the HV/Bias board layout seen in #124 with the six diodes connecting to a common point? (plus the added .01uf 1kv ceramic caps)

Well, I'm glad my questions on my build helped open up some ideas on how #102's HV board works, I hope this helps other builders out in the future!

- Matt J.

[martin manning]

You can add another couple of diodes if you want, there's room on your board. Fender used six, but that was probably a carry-over from when high-voltage silicon diodes were relatively new. Later Dumbles had only four. If I were you, I think I would just rewire it and replace the diodes, with the 0.01uF caps added. If you don't have all the replacement parts, it might just be worth a test with the wiring fixed (and anything that has obviously failed replaced) while you're waiting. It might work!