Been working on my Bally Power Play game. When I got it it had a battery acid damaged original Bally -17 MPU. Thanks to Andrew over at barakandl I installed a modern MPU and the game is running great.
Flashback 25 years ago. Tom Callahan reached out and asked me if I would trial a new MPU he was working on called the Mutha Board. I was flattered and agreed to install one in my home Paragon game. Serial #4 came with Paragon Proms and worked as well as the original, later I used it in my sadly missed Fathom game where Mutha performed equally well as the original.
Yada Yada, 25+ years go by and I was clearing out of a storage locker I had been using, in a box labeled 'pinball parts' I came across Mutha board #4. I thought it would be a great tribute to Tom to put the board back in service. I also love old things that still work, like me. There was some modest battery leakage but only the battery holder was affected. I contacted Clive over at Coinop Cauldron and he sent me a set of proms. I also removed the batteries and added an NVRAM.
To my pleasant surprise the board booted and the game played nominally. The boards test LEDs had failed and no longer functioned but otherwise the game played great freeing up my B&I board for other projects.
This brings me to today, a few weeks ago the Mutha board failed. I noted an issue with the switch matrix where the switch in the row above would register at the same time. Roll over Switch 36 and 35 will show closed. This occurred across the entire row. I assumed that I2 and I3 of the matrix were shorted so I went through all the usual troubleshooting methods. After tearing up the cables I finally reinstalled the B&I board and the game worked fine. Whatever the problem was it was on the Muthaboard. I swapped PIAs, examined for shorts and nothing worked. Putting on my engineers cap again I decided the problem had to be with a bad input cap so I replaced the 330 pf input caps on the affected 'I' lines which fixed the switch problems. While I was at it I replaced the LEDs and now have working test indicators.
Which brings me to today. After replacing the caps a new problem, I was only getting 5 flashes which indicates a problem with the display interrupt. Sure enough a logic probe showed the DIG was locked on. I ohmed out the resistors and replaced the .1uf poly cap. The cap fixed the the DIG and now the board boots.
But now the displays come up flickering. That's usually a sign of a malfunctioning DIG. I replaced the cap again and put in a new 36K resistor and replaced the 555, but same result, flashing flickering displays.
Lots of smart people hear what do you think?
Pictures of Mutha below but my camera cannot properly capture the flashing displays.
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