Bally MCR III Spy Hunter repair after board install gone wrong

Spy Hunter MCR III PCB Repair
- The Board was installed with the main Power Plug connected wrong
- The Story of this board goes when it was repaired for a simple issue
- Board was installed and the main power connector J1 was in 3 separate parts in the cab
- Once the Connector was plugged in and power applied the board smoked
On the Bench test
- 1st thing get the board set prepped to layout on the bench so all 3 boards are exposed for probing
- I used my homemade MCR to Jamma adapter for this. It provides the power,video and control interfaces needed with a single adapter.
- once all the connections were properly made I applied power using an adjustable PSU both volts and amps
- before I connected the PSU I set the VDC to 5.2 and the second PSU set to 11.8VDC for the 12vdc rail on the SSIO
- Power applied! Both PSU’s went into overcurrent mode. Power Off!
- Did an Ohm check between 5v rail and ground rail on pcb showed short.
- Removed each socketed IC one at a time till ohms appeared around 2 continued to remove more ohms climbed
- all that was left was the 6116’s and CPUs
- Re-applied power 5v rail came to life but the 12v still shorted
- Check clock signals all checked good with O-scope and probe
- Found a few Eproms shorted
- Found a couple Caps on SSIO shorted.
- Once all the bad was corrected I finally got an image but not a good one.
- Replaced a few of the color ram and viola we a good image.
- Sound checks passed all is good and working as it should