On many pinball machines like early solid state Bally and Stern games, you’ll often see little capacitors on most of the playfield switches. Sometimes they’re there but a leg is cut off. Why are they there? What do they do? And are they important? We’ll talk about that.
In this latest episode I deal with a sound problem on our Mr & Mrs Pac Man pinball machine. The sound and speech is intermittent and low in volume.
When dealing with any game that is 30 or more years old, you can bet that the capacitors are suspect. These electronic components are known to go bad over time, since they have liquid inside that can dry up, or leak out. It’s relatively easy to acquire and replace the components provided you have the right tools, and then you insure your game board will ideally last another 30 years.
In the video one thing to note is you aren’t always limited to having to find the exact same value/model capacitor. You can replace a capacitor with a lower voltage rating with one of a higher voltage rating. (i.e. replace a 25v cap with a 50v) But you want to make sure the capacitance value (in farads or microfarads) remains the same. You can also replace an axial cap (one with the leads coming out of each end) with a radial cap (with both leads coming out from just one end) as long as you get the polarity properly oriented. Make sure you note that markings usually point to the negative lead, while an indentation on one side of a capacitor will mark the positive lead.
After replacing the caps, we still have some flakyness with the speech portion of the board. I’ve got some replacement pots on order – when they come in I will check on the board traces and solder joints and probably replace that pot… stay tuned and thanks for following the saga!
Probably one of the most common problems people experience with the modern Bally/Williams DMD machines are random resets of the game in progress. Sometimes it appears these resets happen at certain times (like when you hit a flipper or during multiball) and you think it may be directly related to that. Most of the time, that’s not the case, although heavy activity like firing certain solenoids might cause a drain which exposes a weakness in the game’s power system. We’re going to go over the standard procedure to deal with this issue.
After the board is removed, I go over the process to desolder and remove components.
Now time to solder the new components on the board. You have to be very careful to not mess up the traces. There are also some recommended jumpers you can run around the bridge rectifiers to double-up on the traces. I don’t go into that in the video but you can look at Clay’s guide for more details on that.
Another thing you might want to do if you do not replace all the caps, is to mark on the top of the cap the month/year you replaced them. This way in case there’s any confusion, you’ll know which components are newer and which ones may still be original.
The other day the DMD just went “poof” on one of my machines. After doing a little research, and checking connections and things, I realized the DMD board died. In this installment, I walk through the process of rebuilding the power supply-portion of a Bally/Williams WPC DMD board. In part 1 I describe what I’m doing and introduce you to the tools I’m using.
Next up, let’s talk about using a meter to check circuit board traces as we go along..
Desoldering and replacing components.
Now the moment of truth! One thing I want to add is pay very close attention to each item you are replacing on these boards. Two diodes, capacitors or transistors may look alike, but have slightly different values or part #s. The three power transistors and the diodes are not all the same. You may have to bust out a magnifying glass to note the different in the markings on each part. This should also be cross-referenced with the schematics and/or parts list from the game manual.