The WPC  Microswitch

I had a bad microswitch on my Creature. On the left inlane, it would function perfectly in test with a finger press, then fail again after a few minutes. So I decided to section it and show a bit about how these things fail.

A few notes on microswitches.

1) The correct switches for our games are the Cherry DA3 low voltage type. The key parameter is the 0.1A rating. This rating indicates a gold contact that won't film over. The other switches that I see are rated for 5A or 10A. They use more robust contacts that do corrode, and rely on the opening and closing current and voltages to flash through any insulating layers. This corroded switch would probably have worked just fine on 110VAC.

DA3 at BAA $2.95
DA3 w/wire at Pinball Life $2.60
DA3 with flat at Pinball Life $2.35
Happ Controls has them at very aggressive prices in quantity.

2) These things aren't sealed. My game had some moisture problems in the past. This switch clearly allowed moisture and some other contaminant into the switch, which led to the corrosion you see here. Looking at where the corrosion is heaviest, it came from the contact entry side not the button side. So if you dishwash your wiring loom, expect some fallout.



Here's the switch in the open position. The mechanism is simpleif not entirely obvious. There are three moving parts: the button; the contact plate; and the spring.

When the button is depressed, it pushes on the spring. This causes the contact plate to flip over to the other contact.It is unstable in the middle, which is why they always give such a nice snap. 

Here's a view at a slightly different angle. You can see the green corrosion on the contacts.
Here's the switch in the closed position.
And another slightly different view.