I get a "almost every time" ground short row 1 is stuck closed message when turning on my newly acquired Twilight Zone. I've searched other posts and have checked all the switches that are easily accessible in row 1 looking for a short. I also checked fuse F115. I tried unplugging J208 and still got the message.

I'm suspecting U18 on the MPU board. But would like a second opinion before I start board work.

Other interesting facts -

MPU board is original and when inspecting it the only repair I could see was moving the batteries off the board.

I've lost a ball somewhere in the machine. I'm guessing its stuck somewhere under the playfield.

While looking for balls, I opened up the plastic under playfield ramp for the gumball machine. Managed to get 3 balls out of it and already had removed two other balls that were under the apron. After doing this, for one reboot and only one reboot the gnd short message went away.

When I turn the machine on, prior to the error message the machine continually tries to launch a ball from the auto-fire kicker, continually moves the shooter diverter and the clock dial moves.

Thanks for the help!!

Allen

Thanks Lermods - I think this means my MPU board isn't completely fried!

Update - I found the missing ball, it was stuck up in the corner between pieces of plastic. Still getting ground short message.

The thing that is baffling me is the fact that one time the machine booted up fine without the ground short message. I would thing that if I really had an issue with a grounded switch in row 1 that the issue wouldn't happen when I removed plug J208.

Thanks Pin Guy - removed j208 and j212 and still received the ground short message.

Last night I had another successful reboot. Thought I would try and run tests, but the enter button on the coin door wouldn't register. Then I thought I'd try and play a game, but the start button also didn't register.

I'm beginning to think it is indeed a fried U18, hopefully only U18.

Allen

No battery corrosion. I've successfully repaired my Gilligan's Island driver board several times. I think I'll take a shot at doing this myself. If I am unsuccessful, I'll buy either a working OEM board or a new Rottendog.

I'll repost to this thread when I get things working.

Thanks for the help gang!

Thanks Leiden. I pulled the cable and machine behaved differently during the first start up, it displayed very quickly all the audit data. When I shut it down and brought it back up it with the cable still unplugged it went back to the ground short message. I'm certain I have a really sick MPU!

I'm making some progress. After my last post I discovered that fuse F114 was blowing as soon as the machine was turned on. I traced the issue back to a bad transformer. The 13volt AC leg was getting 17 volts. After swapping out the transformer and reconnecting everything I still got the ground short row 1 message. But this time the hard wired switches on the coin door worked. I unplugged J212 and J208 and the error went away!

It now appears to me that the MPU board is OK and that there is really something else shorting row 1. I also get a clock error and the clock just cycles around and around.

Is it possible that the high voltage from the transformer damaged playfield boards? I'm not sure what else the 13v AC tap on the transformer feeds?

Allen