(Topic ID: 156253)

Medieval Madness: Weird column ground short issue


By CookyJar

3 years ago



Topic Stats

  • 14 posts
  • 4 Pinsiders participating
  • Latest reply 3 years ago by CookyJar
  • No one calls this topic a favorite

You

Linked Games

#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.

#2 3 years ago

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

#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.

#5 3 years ago

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.

#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.

#7 3 years ago

Do you have mirror blades installed?

#8 3 years ago
Quoted from markmon:

Do you have mirror blades installed?

Yes, gold mirror blades installed.

#9 3 years ago
Quoted from markmon:

Do you have mirror blades installed?

Can mirror blades cause a short? I've been having a similar issue with my Congo. Replacing the U20 switch chip fixes my column short but had it happen again. I suspect it happened before when pulling out the playfield. My congo has mirror blades and it is a tight fit. Don't see where any wires touch them, though.

#10 3 years ago

Yep. Originally Williams games have wood sides that are non conductive. Moving to mirror blades causes the entire side to become one big ground plane.

I suggest for starters simply in grounding them. The way to do this is in the head. Gold the speaker panel down and you'll see ground braid running to the head brackets. The head brackets are connected to the mirror blades by the head bolts. Simply sever that braid connection and make sure to test it with a meter. Then see if your problems are gone. I always unground mirror blades on Williams machines.

#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.

Promoted items from the Pinside Marketplace
€ 95.00
Lighting - Led
FlipperLED

Hey there! Got a moment?

Great to see you're enjoying Pinside! Did you know Pinside is able to run thanks to donations from our visitors? Please donate to Pinside, support the site and get anext to your username to show for it! Donate to Pinside