Last pinball night was one of those stellar ones where it seems like you can do no wrong. First up was the left flipper not working. A quick visual inspection showed that one of the wires (main voltage to both coils) was broken. A minute later that was fixed.
Next up were the switches. This machine probably hasn’t been played for 10 or 15 years. The household that it was in was a heavy smoking household, and previous to that it was sitting in a barn. It had lots of grime, and most of the contacts for the switches just needed a little TLC. Somebody decided that they should put some oil on certain parts in the machine, and it had gunked up over the last 10 or 15 years. A little bit of IPA goes a long way. A couple plays of the machine also does a lot to clean the contacts. The five bank drop target doesn’t reset when all of them are down, but that should be a pretty quick fix now that I know that it is just daisy chained. I’m guessing that is gunked up and it just needs to be removed and cleaned.
The displays are currently the biggest issue. Replacement displays online are running around $260 for a whole set (Rottendog/Pinside). I looked into the cost of doing it myself from scratch. Looks like $45 for the PCB, $45 for the LCD digit displays, $13 for registers to run the displays, $8 for the MOSFET drivers, and another $10 for connectors/processor/caps/resistors, etc. That gets the cost to around $121. I might be able to cut the cost of the PCB in half, but it doesn’t really help since I’m only going to make one set of these. If I get work to pay for the shipping (i.e. have another board that they need so the shipping for a second set of boards is free), it drops $7. If I didn’t want to add the circuitry to make the displays dimmable, it would only drop out $2 or $3. The other possibility is to try and drop the MOSFETs out and just use the register drivers. That would drop out $8, and if the i2c still worked (which it should), would not reduce the functionality.
The basic design would be an MS9S08SH32 grabbing the row and column strobes from the driver board by polling them. It would then convert the two BCD digits for each strobe into LCD segments and send the information out to each of the displays using an i2c bus and remote registers. Since the segments of the LCDs will be constantly on, instead of strobed like in the original design, the processor is only sending updates so it is really low bandwidth. The project is mainly dependent on whether Mark wants to replace his displays for the $120. The design itself is really simple.