This is another one of those video series where I thought to myself, “If I were smart I would edit this.” But then I thought, I can’t be the ultimate pinball repair guru and I’m not really trying. If I have some kind of “angle” it’s that I’m doing a FPS (First-Person-Shooter) perspective to the hobby, collecting and restoring. And often times when you’re in an FPS, you poke your head down the wrong hall and get fragged. This is kind of how this video series starts off but it takes part 3 to realize the plot twist…
Ok I’ll get off confusing metaphors and back to pinball repair..
The problem I had was when I got this Bally Mystic, one of the targets was broken. I had ordered replacement targets. I opted for the same style as the side targets even though on many Bally Mystics, for some reason, the front targets are bullseyes and the side targets have explosion graphics on them. Go figure? Anyway, after replacing the targets I discovered that two of them would often get stuck in the “up” position and would often not retract when hit. I knew the springs on some of the targets were old and had “lost their zest” (that’s an official technical term by the way). So I thought I’d make a video on replacing the springs, showing an alternate source for some of the components as well as a trick to make an old spring kinda new. Along the way I discovered the real reason why the drop targets weren’t resetting…
In taking an initial look at the latest game I picked up, this Bally “Mystic”, as always my main concern is checking to make sure there’s no significant battery damage on the game. What’s interesting is when I looked at the game, there was no battery on the MPU board. The owners insisted the game saved the high scores, but I didn’t see how? Was there a battery on the underside of the board? I had to pull the MPU out to see.
What I saw was a board that someone had repaired, that had leaking batteries on it. They simply pulled the board and replaced a few damaged components and did not put a battery back in. But they created another issue by not fully-cleaning the board, and as a result, the damage from the leaking battery, even though it was long gone, continued…
The other day I was reminded of how important it is to make sure you fully mitigate battery acid leakage on circuit boards. A friend picked up a STTNG (Star Trek the Next Generation) pinball machine. I’ve been systematically going over the game trying to get it working. When I first looked at the backbox I noticed wires had been run for a remote battery pack – I thought “good deal, one less thing I have to worry about.. the MPU board is clean…” so I went about working on other areas of the game, checking switches and optos and everything. After I got the game booting up I discovered the start button would not work. After spending a bunch of time testing all the wires and connectors and still not finding the culprit I took a closer look at the MPU board where the cabinet switches plug in…
I have seen acid damage before, but nothing as sneaky and widely-spread as this. Components all across the main processing board were showing signs of corrosion and damage, but I could also see that repairs had been done, several components and ICs had been replaced and sockets added. Someone cleaned up battery damage and added an external battery pack. But there was still major corrosion on the board… what gives??
My theory is that whoever cleaned the circuit board, instead of using vinegar and multiple paper towels or q-tips, they probably used a single wipe, and in the process of cleaning the circuit board, actually spread the acid all over the components! At the time, they thought it was clean, but they actually made the problem worse.
This is why it’s very important to thoroughly clean off any leaked electrolyte from batteries, and use vinegar to neutralize it, and use multiple wipes — do not wipe from one area to another area. Work on small parts of the board at a time, throw the q-tip or paper towel away and use a clean one when you start to work on another area of the board. Do not risk spreading the acid to previously un-damaged components.
As many of you know, one of the biggest problems with pinball machines and repairing them is dealing with leaky batteries on solid state machines, that cause corrosion and all sorts of damage. I’m going to go over how you can completely eliminate this from happening by replacing old-style rechargeable batteries with a high-tech “memory capacitor” that will last longer and not have the same problems that batteries do.
Now lets test the new memory capacitor in the game:
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!