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(Topic ID: 257605)

Lamp column not working on Taxi with Rottendog MPU. Need some help to diagnose.


By action76

10 months ago



Topic Stats

  • 5 posts
  • 4 Pinsiders participating
  • Latest reply 10 months ago by ChrisHibler
  • Topic is favorited by 1 Pinsider

You

Linked Games

  • Taxi Williams, 1988
#1 10 months ago

I have a Taxi with a Rottendog MPU that suddenly none of the lights on column 3 are working. I have LEDs in the inserts and you can see them very faintly light up when they are supposed to. They also do this in attract mode. I have traced the wire and it is not broken. I have tested Q62 and it tests fine with a DMM (getting .57 on each outside leg with red lead on tab). I have jumped the tab on Q62 to the tab on Q64 while in attract mode, and the lights come on and flash like they should. That makes me suspect the transistor at Q62, but being that it tests ok, has me scratching my head. I am unfamiliar with the behavior of the Rottendog board so it may be something else I am not aware of. Does anyone have any suggestions of where I should look next and what to test? Thanks for any help you can give me.

#2 10 months ago

Some transistors test good when they are bad.
Power off set meter to continuity place black probe on ground(strap in the backbox).Touch red probe on the tab of that transistor if it beeps it means it’s shorted

#3 10 months ago

Thanks for the tip Mike! I tried this and it seems to still test fine, no continuity between the tab and ground. I pulled the interconnect board and found some corrosion on some of the pins and traces on the solder side. However the pin that controls that column of lights had none on it and I tested the traces on all of them and they all seemed fine. I am going to clean and neutralize the corrosion and then re-flow all of the pins and see if that makes any difference. I am not optimistic that that will fix the issue at hand but it needs doing anyway. I will post the results when I finish.

#4 10 months ago
Quoted from action76:

I am going to clean and neutralize the corrosion and then re-flow all of the pins

I would replace the pins. Any pins that get hit with battery corrosion always gets replaced when I work on a board or wired connector.

#5 10 months ago
Quoted from pinmike:

Some transistors test good when they are bad.
Power off set meter to continuity place black probe on ground(strap in the backbox).Touch red probe on the tab of that transistor if it beeps it means it’s shorted

This works for lamp rows. But you have to check continuity between the tan and the lamp matrix power for this to work on a column. You can use any of the pins on the right side, second connector up from the bottom.

Chris Hibler - CARGPB #31
Http://chrishiblerpinball.com/contact
http://www.PinWiki.com/ - The new place for pinball repair info

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