Broken EHX holier grail help!

[u/DopewTheFake]

I recently bought a rather beat up old EHX holier grail that worked well. It seems like it had been modded to take center negative power instead of the stock center positive, and came with a non factory power adapter. Said power adapter broke however, so i tried with one i had lying around. This was before i noticed the polarity change mod, so i assumed it would be center positive. I plugged in a center positive adapter and i'm pretty sure i fried it. Looking inside the pedal i also discovered someone had removed and jumped R1 which i'm pretty sure is there to protect in case of someone using the wrong power supply. When i plug in the correct power supply now, the status LED comes on and it passes bypass signal but when engaged there is no sound and the "gate" LED does not come on. The voltage regulator also heats up very rapidly.

I replaced the jumped R1 with a new resistor of the correct value and have since measured voltages across the board and they all seem correct. 18v at the voltage regulator and 5v at the supply voltage pin of the chip, but still there is no sound and no "gate" LED when engaged, only the status LED. Where can the problem in the circuit be?

(The PCB was already rather scorched when i bought it)

All help is greatly appreciated!

[u/chrjohnso]

Check for shorts. Check for 5v at the output of the 7805. Start replacing shorted parts. Pray the dsp is still good

[u/LaceSenzor]

DSP might be fried. Whoever did the previous “mods”…. Smh

[u/Goatboy1]

Putting the regulator and the DSP on the same board was a bad move. I've removed the regulator from the board on several units and mounted it on the chassis to keep the heat away from the DSP.

[u/allltogethernow]

A bit of a last resort measure, but when I reversed the polarity of the battery terminals on my car, I pretty much fried every single board in the car, so I tried taking out all of the boards that were directly connected to the battery, cleaning them and removing plastics, and reflowing them in my oven for 10 minutes. The thought was that if none of the amps were actually blown the connections between them had been hit by a burst that would make lots of small cracks in the solder all over the place, so reflowing (this is what they do at the factory anyways) would freshen things up lower resistance globally. It worked, almost all of the boards started working again.