(Topic ID: 156253)

Medieval Madness: Weird column ground short issue

By CookyJar

3 years ago

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  • 14 posts
  • 4 Pinsiders participating
  • Latest reply 3 years ago by CookyJar
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#1 3 years ago

So I'm getting a weird column ground short on my MM, it's column 6 (left ramp enter, left ramp exit, right ramp enter, right ramp exit, left loop low, left loop high, right loop low, right loop high).

I go into switch edge test and hold down any one of that columns switches and get the ground short message, however this happens intermittently. If I hold down one of the switches, but slowly lift/move the playfield the switch will go from the ground short message to registering ok. It also happens vice-versa, the switch will registrar ok, then I move/lift the playfield and will get a ground short. Slight shaking of the machine sometimes produces the same results.

I reseated the connector in the head, moved around the loom under the playfield and checked the connections to the micro switches. I have the gold mirror blades, is it possible that something is grounding out at that point? Doesn't look like it on visual check. I'm open to an ideas, as I'm not sure where else to look. Thanks for any help.

#3 3 years ago
Quoted from DCFAN:

I would look at the diodes on the switches and see if one of them is mashed and shorting.

On quick inspection the diodes seemed ok. I'm going to look again and give a closer run through. Also because of the slight moving of playful causing the issue or making it go away, it seems like it might be something else.

#4 3 years ago

Morning bump, for thoughts on my ground short problem.

#6 3 years ago
Quoted from DCFAN:

Look at all the switches for a frayed wire where they are soldered on. It could be a little strand of the stranded wire is making intermittent contact with something.

Yeah, it seems like it should be something like that. Will check when I get home tonight. Thanks for the tip.

#8 3 years ago
Quoted from markmon:

Do you have mirror blades installed?

Yes, gold mirror blades installed.

#11 3 years ago

Thanks Markmon, will try that. One question what and how am I testing with my meter?

#12 3 years ago

The side blades also have a ground braid, do you sever these too since they touch the head brackets and can possibly continue the ground?

#13 3 years ago

Ok, so I pulled the ground braid that ran to the side rails and since that ground strap touches under the head plate that goes to the other part of the braid that runs to the head brackets I covered it with painters tape so it wouldn't make contact.

Tested the switches and played a few games and so far the ground short problem seems to be solved. Going to do some more testing tomorrow just to make sure. So fingers crossed, thanks Markmon and everyone!

#14 3 years ago

One more possible wrinkle. Played another couple of games and noticed the flashers aren't working, looks like the fuse blew. Hopefully just a coincidence, but I don't have any more fuses left so I'll have to pick some up tomorrow. Hope one of the Radio Shack's nearby are still open.

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