(Topic ID: 335963)

Tales From The Crypt switch matrix help!!!

By MStem80

1 year ago



Topic Stats

  • 4 posts
  • 3 Pinsiders participating
  • Latest reply 11 months ago by MStem80
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#1 1 year ago

I recently acquired a tales from the crypt. It played great for about a day after I brought it home. Then I noticed the crypt tombstone just kept going up and down. Then I realized that the entire switch matrix column that the tombstone was part of went out. Did some research, ended up finding a bad transistor on the mpu, replaced it, game played great again for about 10 minutes. Then the tombstone started going up and down again, and all the switches in that column were out again. Asked a few repair guys, they told me some outside voltage was getting into that line somehow and blowing that transistor, and that I needed to really check all the switches in that line. I did, I changed the transistor, and the game played perfect for a month. Then one day, boom, switch column gone again. Changed transistor, but decided to unplug the motor and see what happened. Game played fine for 2 days with the motor unplugged that controls the up/down on the tombstone. Plugged motor back in, boom, transistor blows. So at this point I think I've figured it out, I order a new motor, install it. Now nothing is working right. The switches are all out of wack, when I turn game on it tells me I'm missing a ball, then it says danger, then it shoots 3 balls into the shooter lane, the shooter switch won't shoot, the captive ball switch has now become the slam tilt, everything is all outta wack. What do I do now? I have only ever touched that one switch column, nothing else. Why is everything going crazy now?!?! Thanks!

#2 1 year ago

Outside voltage is definitely making it into the switch matrix. You absolutely need to try and find out exactly where that is occurring before you waste your time swapping many more parts on the board as it will just keep happing as long as the problem still exist. I know you suspect the motor, and that is a possibility, but it is very difficult for the motor voltage to make its way into the switch matrix the way the circuit is designed. As opposed to coil voltage via a pop bumper, sling, etc, basically anywhere there is coil voltage and switch matrix voltage extremely close to eachother. Sometimes it is very obvious, but most of the time it is a tedious, frustrating search for the point in which two wires are touching where they are not supposed to be. As for your current switch issues, the only thing that can cause incorrect switches to actuate when a switch is activated, besides being wired incorrectly, is a logic issue. I would suspect that at one point in time the high voltage made it's way past the transistor in the switch drive and into the LS244 located at 8J. If not the LS244, then it may have gotten to the 6821 PIA located at 8H via the switch return. A logic probe would be a big help in determining whether the is the case for certain.

7 months later
#3 11 months ago
Quoted from MStem80:

I recently acquired a tales from the crypt. It played great for about a day after I brought it home. Then I noticed the crypt tombstone just kept going up and down. Then I realized that the entire switch matrix column that the tombstone was part of went out. Did some research, ended up finding a bad transistor on the mpu, replaced it, game played great again for about 10 minutes. Then the tombstone started going up and down again, and all the switches in that column were out again. Asked a few repair guys, they told me some outside voltage was getting into that line somehow and blowing that transistor, and that I needed to really check all the switches in that line. I did, I changed the transistor, and the game played perfect for a month. Then one day, boom, switch column gone again. Changed transistor, but decided to unplug the motor and see what happened. Game played fine for 2 days with the motor unplugged that controls the up/down on the tombstone. Plugged motor back in, boom, transistor blows. So at this point I think I've figured it out, I order a new motor, install it. Now nothing is working right. The switches are all out of wack, when I turn game on it tells me I'm missing a ball, then it says danger, then it shoots 3 balls into the shooter lane, the shooter switch won't shoot, the captive ball switch has now become the slam tilt, everything is all outta wack. What do I do now? I have only ever touched that one switch column, nothing else. Why is everything going crazy now?!?! Thanks!

Ever have any luck with this?

#4 11 months ago
Quoted from carvindc200:

Ever have any luck with this?

Yeah I fixed it, turned out a screw on the motor was missing it's washer and that allowed it to come in contact with a piece of metal.

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