New Life Games Tech Forums

How to accurately check closed switch contacts.

When you are checking any of your relay leaf switches, remember that to actuate them properly, you must simulate what the machine does.
Push down on the coil armature (flat plate), and NOT at the fiber or plastic assembly which operates the switch ends.  Doing that pushes down the actuator blade further than the machine would normally do it.  There's some slight slop there.
Many folks have adjusted their switches doing that, but often they do not fully contact, or, even worse -- release  -- (which could lead to burning coils if something is stuck on.)
Look for the actuator blade to slightly physically push the static blade when it contacts.  And also make sure they cleanly open.
Always adjust the static blade(s) to the actuator(s).  Only bend the actuator if really really necessary.
Always adjust the blade nearest to the stack of micartas (insulators) rather than at the other end.
If your machine has come from a wet climate to a dry one, you might want to slightly snug up the 2 screws that hold the switch-stack together. 
Here in Reno, we'd have to do that to all new machines after a few days, because the machine heat would drive off moisture into our dry air and the stacks would loosen.
Unless your switches are arcing a lot, you shouldn't have to often clean contacts. Very rarely if at all.  If they push and move when contacting, they should be self cleaning.
If you're familiar with your machine, you should be able to check every switch on it in a few minutes.
OK, I'm timing you....

Now, if you want real accuracy checking switches, use your VOM. Especially if you have to troubleshoot.

If you have gotten a new machine, with any problems, one of the first things to do is go through and check all your switch stacks.
Might fix those problems.

Note, something important came to mind for when you check your switches with an ohm-meter.

It is vital that you check your switches by placing the leads of your meter onto the tabs of the switches (where the wires are soldered in), rather than touching the switch leafs themselves with your probes. 
If you touch the leafs, you are liable to put extra pressure on the switch, and thus force it closed when it is not really making contact.  This in turn may lead to your mis-diagnosing the problem, and looking elsewhere, when in fact that might have been the original problem.

Checking your switches in the correct manner will lead to much much more accuracy.
And, again, look for some movement when your switches naturally close, that lets you know they're making contact.  If they are clean, and you see some 'push' when they close, then they are probably 100%.

This may be a silly question...but...could you draw a big picture (or use a photo) of a typical switch and label the parts? I know this is simple stuff for you and others who work on EM's but I just learn better by pictures!
Okay...Sunday...off to work again, but not on slots!  :60-

Well, I can draw one but don't know how to post it.
Basically you have two leaf switches, the long one is the actuator blade, and the shorter ones are the static blades.  They are all held together by micarta insulators, with a plastic tube inside to keep them insulated.  It can sometimes be a pain to take them apart, so don't unless you really have to.  If you find continuity between any switch, and the case, that might be an indication the plastic tube has broken down, and the switch is touching to the screw that holds the stack together.  That doesn't seem to happen very often, though.  Also, between sets of switches which are not supposed to make contact, there are usually some kind of paper or other insulators to keep them from touching, if they'e not supposed to.  You should always try to adjust the static blades, rather than the actuator blades.  If possible.  As you have seen there are different sizes of them, etc., but they should all act the same.
Mebbe I'll get some paper, and take a pic, but my drawing skills are pretty poor.
And, again, try to measure continuity at the tabs, where they are soldered, rather than pushing on the switch blades themselves.

Also, you can often clean a switch quickly, just by raking them with the end of a small pocket flat blade screwdriver.  That is often enough to shake off the carbon buildup. Used that trick many times on the floor, for when you don't have a can of solvent or contact cleaner with you.