Just joined and posted this in the Black Hole club but this might be better as its own topic. For what it's worth I have pretty good proven experience resurrecting complete wrecks and rebuilding boards in WMS Sys 6/9/11, Bally/Stern -35, and GTB Sys3... but this (BH I just picked up that hadn't been put together in years) is my first System80.
Current state:
I am aware of the ground mods and am implementing them but want to get the game to boot first. So I've grounded the MPU, Driver, and Power Supply, down to the ground strap. I added the extra wires to the MPU / Driver interconnect. The MPU has the "slam switch mod" added. I've verified proper power (5 / 8 / 42 / 60) at the power supply. All fuses have continuity. Transformer voltages look good. Rectifier voltages look good. I added the 5V status LED to the MPU and that lights up.
What happens:
- At power on, (most of) the Playfield GI turns on but there is NO backbox GI aside from the chase lights (yay, aux light board works). Wait a few moments and maybe you'll hear attract speech (yay, speech board works!). But there are NO no controlled lamps / attract mode, no score displays*. I get the playfield "coil thunk" momentarily and that's it.
(*Score displays are actually about 50/50 odds of them being all blank, OR three of the four illuminating a couple "half characters" like backwards little c's instantly. BUT when I turn the game off I can briefly see all segments on all four displays light up right as power drains... so the displays are hopefully/probably good). Occasionally there may be a couple controlled lamps stuck on but like the displays or activation of the sound card, this is inconsistent.
Clearly the game isn't booting... but I don't think that's the only issue.
Further troubleshooting:
6502 chip is high on pin 40 and pulses clock signals on pins 39 & 37. All 3 RIOT chips share the pulse on pin 39 too. SO that means the reset circuit is working. But when I check IRQ on the CPU p4, it's stuck high.
Unlike posted guides for WMS and Bally/Stern, there doesn't seem to be much posted on troubleshooting these. It's all "do the ground mods and there you go". Not much in the realm of further or basic troubleshooting... not even to answer if the MPU would boot without the Driver board attached...?
I do have the schematics and can make some general sense but am still likely to miss things. Can anyone help with guidance for tracing signals, next chips etc, to figure this one out..? Thanks....!