Finally got my board operational again
Quick recap on timeline, issue, and resolution FYI:
Rev 6 board, G Pal
Received CPS2 Multi, removed roms, plugged CPS2 Multi - all worked fine
Re-seated multi several times due to the crackling audio. Didn't resolve the crackling, but all still working fine.
Got the reinforcement boards - removed CPS2 Multi, applied, re-seated, all still working fine.
FrancoB kindly lent me his kit to upgrade the firmware for auto reset.
Removed CPS2 multi, upgraded firmware successfully, re-seated - sound suddenly garbled.
Re-seated and played about with seating at least 20 times, did the leg lifting, wire connection for the G Pal, even though it shouldn't need it - no change. Still garbled sound.
Visually inspected all jumpers (don't have a multi-meter to properly check) all looked good.Decided to cut all open jumpers, just in case they had somehow re-bridged
Re-seated CPS2 Multi - all working good again.
For me - the garbled sound issue was definitely an open jumper that had worked fine for weeks, but then decided to somehow re-bridge. Shame I didn't have any testing kit to pinpoint which jumper(s) were the cause.
Bloodhokuto - how is your board performing with the case causing an issue when put on? I'm wondering if possibly it's a similar issue - an open jumper that has such a fine clearance, that when a bit of pressure is applied, it causes the board to bend very very slightly, but enough to bridge a gap on one of them?