Hi all, I picked up a "broken" EH Holy Grail Nano for cheap, and the issue is that the DPDT (on-on-on) Reverb Type switch was broken and stuck on 'spring'. I pulled it apart and tried to replace the switch with an off-board DPDT, and nothing is changing with the switch. I started trying to connect each lug to ground separately, and all combinations of them, and I couldn't seem to get it to change then either. The DPDT switch I pulled out was definitely broken, the sliding metal contacts inside were cracked along with part of the plastic mechanism.
Does anyone know logically how the switching works here? I've found a couple of other Holy Grail derivative schematics (here:
http://music-electronics-forum.com/t41446/), and they seem to all be slightly different variations on pulling some logic pins to ground. The Nano has a different main DSP chip, with datasheet here:
https://www.nxp.com/files/dsp/doc/data_sheet/DSP56374.pdf. When doing a continuity test though, none of the pins of the switch connect directly to any of the pins on the chip, except the one that goes to ground obviously.
Is there anything I'm missing? Is the RESET function important while switching, or just power-on? Should I be connecting some voltage here? I'm hesitant to try because of the delicate specs of the DSP chip.
(Posted in the DSP forum because I'm trying to understand the seemingly digital logic behind the switching, if that's wrong, let me know)
(End game for this is that it's going in a combo pedal with a fuzz, so if all else fails and no one has any clue what black magic EHX does, I'm fine with just using the hole I drilled for the switch for a filter or something)