(Topic ID: 188743)

EM Tech Assistance Needed

By whthrs166

2 years ago

Topic Stats

  • 9 posts
  • 6 Pinsiders participating
  • Latest reply 2 years ago by phil-lee
  • No one calls this topic a favorite


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#1 2 years ago

I was working on a Sonic Mars Trek this week and I had one problem with my bonus lights not lighting up on the playfield. I went to the bonus unit and just wiped down the contacts on the board and spider. No change. (this machine is in very good condition with very low play time) The contacts on the bonus unit looked perfect. So then I got out some metal polish and polished the contacts again and made sure the spider contact arms had good tension on the board contacts. No change. So this time I took the bonus unit, apart took spider out and tested with the continuity checker on my DVM all of the contacts on the end of the spider arms and none of them were making good contact with the arms! Hmmm ??? So I took a hammer and I Gently tapped down the rivets on the backside of the spider arms then tested again and got good contact. Put it all back together and it works perfect. My Question: is this situation common in EM games?
Do these contacts in these units (bonus, ball, player ect...) have this problem? Or is it just in the Sonic games?

#2 2 years ago
Quoted from whthrs166:

is this situation common in EM games?

I wouldn't say common. Any leaf blade switch can have the contacts not making good contact.

If it happens, I usually silver solder them so it doesn't return.

LTG : )

#3 2 years ago

Ok thats good to know. The peaning seem to work on this one. I just wondered if i needed to expect this sort of thing down the road. Thanks

#4 2 years ago

Typically, the way to get good contact is to lightly sand the rivets with 400 or 600 wet or dry sandpaper and use 90 isopropyl alcohol as the lubricant for the sanding. Clean of off the residue and use a dielectric grease to ensure continuity and free movement. Superlube is the preferred grease.


I've never fixed a stepper, TV or computer with a hammer.

#5 2 years ago

I cleaned the contacts so clean they looked like mirror. That wasnt the problem. The problem was the contact was loose on the spider arm ( all the sanding and buffing in the world wont fix that) i had to tighten the contact to arm by peaning the rivet that fastens the contact to the arm

#6 2 years ago

In my experience, this is not a common issue. When cleaning steppers, I lightly file down the contacts on the spider. I've never come across one with a missing or loose contact. I once had a relay with a missing contact on a leaf, but I've only seen it once.

#7 2 years ago
Quoted from whthrs166:

The problem was the contact was loose on the spider arm

Sorry - don't know how I missed that. In this case, it looks like the hammer was the answer. I've fixed loose contact in blades before with solder. Never on a stepper.

#8 2 years ago

PBR-Grease works great for lubricating steppers, I use it to lightly coat the contacts on the disks and the main spindle. Its cheap and as with any lubricant on a pinball machine, less is more.


#9 2 years ago

"Ghost" contacts on leaf blades appear to be solid but just don't work,or work sporadically.
Silver solder is the best application on an old part. Replacement with a new leaf/contact is better.

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