One thing to note is that Data East pinball machines can act *really* strange when one little thing doesn’t work. I’ve seen a simple blown fuse cause a Time Machine to act so bad I almost started looking for another logic board.

The Time Machine had a ball sitting in the lock, when the game was powered on it just kept firing a bunch of coils in succession. The game knew ball was there, but it was trying to release it so it could go back to the trough. After a few seconds of this, the coil firing got faster and weaker. The odd thing is none of the fuses looked bad. That’s why I always say, you have to measure them when in doubt to be sure. I can’t tell you how many times I chased around a problem only to later find an unobviously blown fuse.

This Teenage Mutant Ninja Turtles worked fine for a few days when all of a sudden it would kick all the balls into the shooter lane and keep firing coils including the ball kicker. After a few moments, it would stop. Now, when I say “all of a sudden”, what I really mean is someone F-ed with it and it stopped working right. More on that later.

What happens as you’ll see in the video is that the ball kicks into the shooter lane, then it kicks the rest of the balls, and the coils keep firing rapidly for a few moments then it stops. What’s supposed to happen is the game kicks one ball into the shooter lane, then the left/right relay switches sides to allow the flash lamps to do their light show, then switches back to coils.

The purpose of the left/right relay is to increase the number of coils and flash lamps the game can drive and Data East games have a LOT of flash lamps. The logic/driver board only has so many transistors on it. To be able to drive more coils and flash lamps, a left/right relay is used. In this game, the relay is set to kick the ball into the shooter lane, then it switches to flash the flashlamps in the backbox.

The reason it was firing coils rapidly is the game is trying to flash a bunch of flash lamps, That’s why the coils were firing so fast. But the left/right relay wasn’t switching to the flash lamp side. After some troubleshooting I found that I could short the drive transistor to ground and verify that the relay works, but when I activated it a bunch of flash lamps locked on.

As I went down the line I found one transistor was pulling a lot of current and the clip would almost “weld” itself to the transistor tab. When I did that long enough the coil fuse would eventually blow. What ended up happening was someone plugged the G.I. relay control plug on the power supply backwards. You can see in the pictures below, I had already cut and repaired the connector before taking these pics, that’s why the wires are missing. It shows how easily the plug could be reversed.

Because this plug was reversed, it shorted the diode on the G.I. relay. This caused a voltage spike to take out the 74LS08 which is an AND gate, it’s part of the blanking circuit. I’ll go into more detail on the blanking circuit in an upcoming post.

Fortunately, the damage stopped at the 74LS08. Sometimes the voltage spike goes back further and takes out the 6821 PIA. With 40 pins, the PIA is a pain in the ass to change.

Once I repaired the GI relay control plug, replaced the coil fuse, and replaced the 74LS08, the game was back to normal. You can see what the game was doing and how I repaired it in the video below. Sorry the video ends abruptly, as I say in the intro, I wasn’t planning on shooting a video when I started and when I shot the intro I didn’t think of shooting an ending.

Hey, if you found this informative, educational or helpful in fixing your games, please share it!

Till next time, Frank

Grab a battery board for your Data East pinball machine and forever protect it from battery corrosion damage!