I was going through some old videos that had been uploaded to YouTube that for some reason were not made public and found this one. It’s a short video on how to go through the diagnostics on these 80s era Bally pinball machines and track down switch matrix issues. I don’t go into how the matrix works in this particular video, but I do demonstrate how a stuck switch can cause odd behavior. In this case, the tilt triggers when a certain target is hit.
This is a game that’s been sitting in the back for awhile at my place that I keep meaning to get to, so I finally jumped back into to figure out what was wrong. It’s weird to go over notes you made 6+ months ago and try to pick back up where you left off — remind me not to do that.. LOL But the issue was relatively simple: The center bank of drop targets was not resetting.
In this series of videos, I go over, step-by-step the process of how to figure out what’s causing this problem, how to read schematics and manual diagrams, and the various points of failure, and once again, we are reminded of “Ockham’s Razor” which suggests the most obvious cause is the most likely… OR IS IT?
Interestingly enough, once I figured out where the problem was, rather than solve it the traditional way, I choose to do a “hack”… basically just to see if I could do it. The choice was, do you replace an entire 16-pin IC that’s only using one small part of it (involving adding a socket and a new chip that is pretty expensive and hard to find) or do you “hack” the damaged chip and piggyback a new component on top of it? Normally I don’t do these kinds of MacGuyver stuff on system boards, but it was a fun trick to try and it cost a few cents and about 10 minutes verses a lot more time than would have been used to replace a whole IC.
One reason why this hack job is particularly sloppy is because I had to work on the board in the game due to the previous owner having hard-soldered some wires to one of the connectors – that’ll be another future project to clean up all that mess, but for now, I needed to get this back working.
To understand what I did, here is a substitute circuit board showing the position of various individual 2N4401 transistors overlaid on the CA3081 IC package. Using this you can figure out where to insert a transistor manually on the IC pinouts if one of them fails:
This is one of those pinball pickups that we all dream about. It took me awhile but I finally had one of those experiences. A top-5 grail game, in HUO condition? Way below market value? Sign me up!!
This is also one of those games I’ve toyed with selling on and off because it’s so beautiful and desirable, but so far, we’ve kept it.
Here are some pictures of the game showing its condition:
The other day I was working on a game and traced the problem back to a blown bridge rectifier, so I thought it might be nice to produce a short little video on how to test/check bridge rectifiers in pinball machines, as well as a little info on what they do.
Diagnosing problems with the mist multi-ball assembly on a Bally/WMS Bram Stoker’s Dracula pinball machine. In this case, we were not getting power to the motor, which is supplied from the 20vdc circuit on the power driver board (which also powers the flash lamps). In this series of videos I show how to test the mist motor, and where you check for power and back-trace it to the driver board, then identify which components are related to this problem and how to fix it.
If you have a broken plunger/linkage, you can repair it and replace the broken part for a lot cheaper. Sometimes you can’t find complete linkages but you can get the individual parts or the linkages. Here’s how you can build them, or repair them. It’s been awhile since I did this so I had to refresh my memory of how I did it.
