Author Archive: dave

Bally MCR III Spy Hunter repair after board install gone wrong

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  • 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

Bally MCR Tron Repair Log

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Problem: Game Plays but no Sound

  • Troubleshooting Steps taken before benched: Fuses Checked
  • Ohm checked Volume Pot
  • Ohm checked and voltage checked cables going to the amp PCB
  • Checked 5v,12v rail on SSIO PCB

Troubleshooting on the bench: Did a Sound and channel test (Failed){Used O-Scope on output of 8910s)

  • Using digital Probe: Found Pins 27-29 on both F6 and F7 had a binary number of 010 which set the 8910s to inactive during any test that was ran
  • Starting checking all Address and Data Buss only on the Sound Cpu side to verify pulses through buffers.(ok)
  • Checked IO signals to from B13(ok)
  • Downloaded a Test Rom to run more thorough direct test on the SSIO
  • During a Square wave test on F6(this test bypasses any of the watchdog circuitry on the board) The Sound was very Low and square wave output was minimal
  • Started probing control circuit for wave output and panning.
  • Found that the RC signal on D11 was Dead
  • Replaced D11 and Sound now works as it should.