Dolly – why won’t your switches work for me? – aka the Bally Pinball switch matrix

U8 image

U8 image

I have been trying to figure out how to address the Bally switch matrix.  I have found (as I have recorded on my issue tracker) that I have 8 switches that aren’t responding.  I looked up how to build the visual diagram of the switch matrix – a grid of 5 columns, and 8 rows.  The first column (0/zero) has switches 1-8, the second column (1/one) has switches 9-16 etc.

I have laid out all the switches based on the game manual and number allocation assigned to each switch – and have determined that 7 of the switches that are out are all on the same column (switches 17, 19-24 – switch 18 is unused), and then switch 34 for a 30point rebound is also out. If this was a Williams game I’d know better how to approach the problem, but Bally addresses the issue of switch management differently – particularly in relation to the matrix.  I know it is handled in one of the two PIA chips (U10 I believe).

I have determined that connector J2 Pin3 is the one that feeds the column.  Now what, not 100% sure :).  I’m guessing I need to make sure I’m getting continuity somewhere else – but haven’t determined that yet.  It is 1am, and I’ve been working on the game for 3+ hours at this point.

Hopefully, one of my great friends will have an idea of how to resolve this.

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2 Responses to Dolly – why won’t your switches work for me? – aka the Bally Pinball switch matrix

  1. David says:

    Just a quick update – a guy here in Georgia who is also a member of GAPAS wrote the following:

    I’d make sure the connectors aren’t causing the problem first, cold/cracked solder joint, flaky connection. I had several lights on a Space Invaders that were out. A few were driver transistors, but at least two of them turned out to be bad connectors. Replaced just those with trifurcon pins and everything was fine. Contacts had broken apart in the housing. Just a continuity check should catch if that is the case.

  2. Harry Knutz says:

    Do the switches not work in the test mode, in game or both?

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