Do leaf switches ever really go bad?

Stuffmonger

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I don't really see how a leaf switch could really go bad other than surface oxidation/rust, but the player 1 start button on my joust doesn't work, and it appears to be wired up fine. All I can really think to do is get some light sandpaper and clean up the contact spots on the leaf switch. any other ideas?
 
Leaf switches very, very rarely actually "go bad". Usually they just get dirty. To clean them, just put a scrap of paper between the contacts, push them together to put pressure on the paper, and slide the paper out. Should get a little dark line of crud on the paper.

I've seen end of stroke switches in pinball machines go bad though - they start to get real pitted and arc, but those are high current.

Usually, when a button doesn't work like that, it's not the switch itself, it's the wiring, or the connector pins on the board - especially on Wiliams games. Usually, there is a cold solder joint on the connector on the interface board. Or, one of the buffer chips has a bad gate. Easy enough to check though - just put a screwdriver or other metal object across the side of the switch, joining the two blades together, bypassing the contacts. If that works, then the contacts are dirty. If it doesn't, then you have some other problem.

-Ian
 
They do go bad. I've seen the pads fall completely off, others on pinball flippers, I've seen burned or burned right through.

You are not supposed to sand them though!

Clean with alcohol and a swab, or sandwich a business card between and pull through.
 
Leaf switches very, very rarely actually "go bad". Usually they just get dirty. To clean them, just put a scrap of paper between the contacts, push them together to put pressure on the paper, and slide the paper out. Should get a little dark line of crud on the paper.

I've seen end of stroke switches in pinball machines go bad though - they start to get real pitted and arc, but those are high current.

Usually, when a button doesn't work like that, it's not the switch itself, it's the wiring, or the connector pins on the board - especially on Wiliams games. Usually, there is a cold solder joint on the connector on the interface board. Or, one of the buffer chips has a bad gate. Easy enough to check though - just put a screwdriver or other metal object across the side of the switch, joining the two blades together, bypassing the contacts. If that works, then the contacts are dirty. If it doesn't, then you have some other problem.

-Ian

Tried the screwdriver bypass, and it registered just fine. Tried the paper thing, and it made no difference. From the looks of it, I've got some pretty bad oxidation on the contacts. Why is fine grit sandpaper bad (240 for example)?
 
Tried the screwdriver bypass, and it registered just fine. Tried the paper thing, and it made no difference. From the looks of it, I've got some pretty bad oxidation on the contacts. Why is fine grit sandpaper bad (240 for example)?

OK, yeah, then you probably just need some more thorough cleaning. Generally you don't want to sand them because it's easy to get them filed at an angle. But, if the switch is visibly corroded, you can sand them - in pinball machines you typically use a flexible file or a fingernail emory board. Fine sandpaper works too. The problem with sanding contacts is really more of a thing where people think they need to sand all of them, and they file them down way too much. Just a little is all it takes. And on pinball contacts especially, things can get really mangled when someone goes all-out filing and bending contacts.

Also, we're talking about a start button here. Hardly something that needs to be precise.

-Ian
 
The thrust button leaf pad was acting intermittently on my Asteroids. I discovered the pad was loose going through the leaf. Added flux and solder to the back of it at the rivet and it was solid and fixed. But hey, things happen to both no, low, or high current leafs, just luck of the draw.

If their really oxidized and nasty with tar build up, or are just weak from people bending them too much, or fatigue from years of use, I'd replace them. I replaced my Asteroids fire button leaf. The metal was weak from all the years of firing it did! LOL!!!
 
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Tried the screwdriver bypass, and it registered just fine. Tried the paper thing, and it made no difference. From the looks of it, I've got some pretty bad oxidation on the contacts. Why is fine grit sandpaper bad (240 for example)?

Because it will take the layer of gold plating off. Most original leaf switches have a very thin layer of gold on the contacts to prevent ozidation. What you are probably seeing is the accumulation of airborne crud which does build up, especially in games that spent a big chunk of their lives in smokey atmospheres (bars and older arcades that allowed smoking).

The best thing in that case are some of the achohol wipes that they use in Drs offices as antiseptic before shots. If you can't find those, then the premoistened eyeglass cleaning cloths work well also. Open one of those up and slide it in between the contacts (while pressing them together) and work it back and forth. Then try an index card or a white paper business card. Keep going back and forth untill the card is clean when it is pulled out.

ken
 
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