I bought a pinbot from a guy about a year ago.
Broken project that wouldn’t start.
The guy let me know he already bought a new rotten dog power supply and new U26 & U27 ROM’s but it still wouldn’t start. No leds on the board at all, +5 volt, diagnostic, blanking. And he was burnt out trying to fix it.

I just finally got time to look at it.
This poor guy must have had the worst luck.

Step 1-
The brand new power supply wasn’t putting out +5 volts, so I swapped in a known working one.
Still only light that would come on the board was the +5 volts led.
All other voltages checked and confirmed good.

Step 2-
Took me a bit before realizing to check the brand new ROMs he had purchased (preburnt from a dealer). Replaced one of them (can’t remember which) and the diagnostic led lit up, but still no Blanking LED.

Step 3-
Replace the other ROM and now the board boots and works fine. +5 volts LED, diagnostic LED and Blanking LED all working.

Game now boots and plays.

I’m posting this because I’m still fairly new to board repair and there wasn’t much info out there saying a bad ROM would stop the LEDs from lighting. Maybe this is common knowledge and I just missed it.

This just might help someone if you have the same problems. Check your voltages and check your ROMs.
AND DON’T ASSUME NEW PARTS ARE GOOD, sometimes there messed up to.