I saw a set of relay points that needed a file once or twice - I think those got replaced.

99.99% of my EM points just need a bit of gentle cleaning.

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I make contact cleaners from 400 or 500 grit wetsand paper and double-sided Scotch tape. I cut the strips with a pair of those freebie scissors from Harbor Freight.

If you have a Dremel tool, I think it's much better and faster to use a wire brush attachment on your Dremel to clean switch contacts. The #443 brush is great for getting into tight spaces like those lower-level motor switch stacks, and the #428 brush is great when you have the room to get access to the switch contacts from the side.

- TimMe

Seems like the wire brush from the dremel would catch on the leaf of the switch and twist them? I like the idea but...

It's good that you're cautious. If you've got some old salvage parts around, give this method a try and see what you think. I know it sounds aggressive but it doesn't cause any damage to the switch blades or contact points, and it works like magic.

I've personally been using this method for over 15 years and have cleaned literally tens of thousands of switches. I've never messed up even one switch contact or bent one switch blade. I've used it on all kinds of EM switch stacks - very small to very big relays, motor switches, relay banks, score unit switches, flipper switches, EOS switches, etc.

I use a medium speed setting of the Dremel. I've never tried cleaning contacts with the tool running at top speed, so I suppose there could be some risk if someone were reckless enough to do that. As with any power tool, there is an expectation that you will pay attention to what you are doing and use good judgment.

For 100% disclosure, it's true that I did run into one issue with this method. This was on the older Gottlieb "R" type relays (the ones from the 40s and 50s made by Potter & Brumfield). These relays have rather delicate pigtail wires that attach the armature switch blades to the solder lugs. The Dremel brush snagged one of the pigtail wires and ripped it loose - a good example of not paying attention to what I was doing. Other than that, I've never had a problem with this method.

- TimMe

Thanks for the feedback I'm going to give this a try on my Aztec.
Don

This has been my preferred method for quite a while as well. I was introduced to it by none other than....TimMe.

The only real downside is that the relay generally needs to come apart. The upside is that 99.9% of the time, it is one and done on this. You clean it and you are done for good. It takes about 3-4 seconds per contact.

A downside that has been mentioned to me on these forums numerous times in the past is bits of wire wheel flying around and shorting/making a mess of things. This is always mentioned by people who haven't ever done it. In reality, I never have had this issue.

Personally if I ever used a Dremel tool on contacts I'd use a fiber brush instead of steel for the flying wire bits.

With that said, the fundamental reason a contact will need cleaning is to remove an insulative "something" that is preventing it to conduct properly.
Dust accumulates on contacts and burn leaving carbon. If the current flow is sufficient enough it burns a pit in the contact and leaves more carbon.

For the low current applications like turning on a lite etc not much pitting or carbon accumulation occurs so I just fold a clean scrap of copy paper about 4x into a stick, put some rubbing alcohol on it to clean the carbon off.

Filing and sanding should not be the standard default method of cleaning every problem point.
Nobody has said it is, but i wanted to make it known. Removing a bit of contact material is usually necessary on those harder contact higher current switches such as flipper and 120v bank reset solenoids but not on a smaller, softer player 3 lite contact.

I use a hard mini small file when a few swipes with a file is necessary. I've had occasional bad luck with flexstone and wet dry sandpaper.
The problem I have is I trace an issue to a particular switch or segment of circuit and think I am cleaning the switch. .. and it looks clean too. But bits of sand had come off the paper and is left in the contact so it still doesn't work and I chase my tail looking for trouble elsewhere.

I still use the wet dry sandpaper if I can't find my file - but only if the alcohol method fails to get good results. I stopped using flexstone though for those issues .

Steve, I can assure you that the #443 brush does not produce any flying wire bits, at least not in any quantity that is detectable by me. It certainly doesn't do anything bad to the circuits in an EM pinball machine.

I have had wire bits come off of the #428 brush, but I have NEVER seen this cause any problem in an EM pingame circuit. I think the bits are just too small to cause any trouble there. The main problem I have with these bits is that they occasionally get stuck in my skin like a little metal sliver, and that is rather annoying. I normally use the #443 brush to avoid this problem, but sometimes I still like to use the #428 brush on larger contact points.

I gave up flexstones and sandpaper a long time ago for the very reason you sited - they often depost grit and glue residue on the contact points and that can cause a circuit failure. One of the (many) reasons that I like the Dremel method is that it does not have this problem.

- TimMe

Here are some pics from a tech talk I did 8 years ago showing the Dremel cleaning method. This is with the #428 brush.

- TimMe

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I was anti Dremel wire wheel until I tried it on some junk switch contacts. It really does a nice job & if you follow up with compressed air you minimize the chances of a stray wire shorting something out. I have yet to have issue with it.