How to "check switches"

Hi All,
This gets asked enough that I thought I'd write a "sticky", and hopefully it will be read, before it's asked again ???
For any set of contacts, open or enclosed, a GOOD analog meter is required, set at "X" (or "R")-1--digitals will not do it !
If an enclosed three terminal "Micro Switch" (brand), or any similar type of switch, I connect one meter lead to the com. ( remove any wire there for the test), and the other to NC. At that point I s-l-o-w-l-y actuate the switch. Meter must NOT move, while switch is being pushed, until AFTER it "clicks". Once it clicks, the meter should show an open. I then run the actuator in the other direction--slowly--Once it clicks, again, I watch the meter--it should make with a near zero reading, and hold it all the way out--. If it does not fail, I move the probe to the NO terminal, and do the same two tests (it should read backwards, to the NC tests).
For open blade contact points--remove one wire--connect the meter to the two terminals, and actuate the switch. These switches having silver contact points, must be "clean", free of "pits", and/or burned areas. A "contact point burnishing tool" is recommended--I do not recommend "sprays", other then, a "plastic safe - non residue" type is OK, to wash it. If pitted/burnt, a file must be used, followed by the burnishing tool -- NO "sandpaper" of any type, IMHO, should be used. Contact area must have silver on it, or it needs replacement--Gold contacts, usually turn black--no file, or burnisher should be used !! If not burned, a SMALL dab of Deoxit 5, or better yet, Deoxit "gold" may be used. A burnt "gold contact" may be filed/burnished, but it will not last too long after that---should be replaced. Ron Rich

On occasion, in hard to reach areas, I like to use 1000 grit emery paper to polish contacts.
Works fine, gets the job done.

Hi Matt,
"Gonna hafta agree to dis-agree", here. If you ever look at silver contact points after they have been "cleaned", with any kind of "sandpaper", under the microscope--You will notice that the Grand Canyon runs thru them. In some cases, you will notice that there are also "mountains" in them--these are embedded bits of the sand, from the paper. When properly cleaned, with a burnishing tool, they look smooth as a baby's bottom.
One thing I failed to mention yesterday, properly adjusted, contacts ideally should "make", then "wipe" about .015 of an inch--UNLESS the "crossbar type", which should "just make, firmly"--no wipe.
Ron Rich

I would like to inject some things here as someone at this type stuff for over 40 years . You dont always have to unhook a switch to test it . You can first test it in circuit and if it tests fine then ok . If it acts way off then unhook it . I say this to help save time and .... if you can imagine a newby unhooking every contact and switch in a jukebox who has poor soldering skills , it would make things worse .

Analog meter ? i retired mine 25 years ago . I have no problem with a digital meter on switches . They are more accurate when i use one . The biggest problem doing this is getting the meters leads to make 100% contact during a test . A set of test clip leads seem to work well here .

And about deoxit . I have tried that stuff and it works well at first then after a short time it fails , noting some switches never stay clean . Then what does one use ? hard to say , several things will work better that are 1/3 the cost .

Contact cleaners . I use these every day in my shop/business . You are limiting yourself if you only use the light duty sprays . I have saved hundreds of switches and lots of time using a strong ( will melp plastic ) type cleaner . You have to use common sence using this type cleaner so you dont ''let it fly'' onto cabinet parts and some plastics or drip down onto the wrong place .
After these '' removes all oils'' cleaners it is necessary many times to use another spray with some light lubricant in mechanical switches .

With regards to the micro switches used on the Rowe Ami jukeboxes 1963 Model L 1100 mechanism through to 1979 R-83 1200 mechanism that uses the same micro switches on the cam switch cluster and in the case of the 1100 mechanism on the stop plate assembly and dentent. In the 35 odd years that I have been working on these I have never had to replace a switch (unless it was physically broken i.e. plastic case broken) I have adjusted many that were incorrectly set.

Over the years I have worked on hundreds of these mechanisms and at one stage we used to manufacture hideaway units using referbuished mechanisms.

There seems to be a trend in replacing things just for the sake of it. Prevenative maintenance is one thing but the old adage "if its ain't broke, don't fix it" still has a place in engineering.

These are only my mumblings of course

Regards
Alan

Hi All,
IMHO, the open blade type of switch, should NEVER have any "coatings" of anything on it.
If set correctly, the "wipe" will keep it clean enough to function. The "Micro Switch" type are, in theory, supposed to never "become intermittent", and are supposed to "snap" at exactly the same spot every time--I won a bet with one of their engineers over this, along time ago--proved to him,( using brand new switches), that they do NOT switch, as above at all times--
As for an Analog, vs, a digital meter--the analog will show a "bad" switch", that a digital will show as good !
Ron Rich

Ron Rich wrote:Hi Matt,
"Gonna hafta agree to dis-agree", here. If you ever look at silver contact points after they have been "cleaned", with any kind of "sandpaper", under the microscope--You will notice that the Grand Canyon runs thru them. In some cases, you will notice that there are also "mountains" in them--these are embedded bits of the sand, from the paper. When properly cleaned, with a burnishing tool, they look smooth as a baby's bottom.
One thing I failed to mention yesterday, properly adjusted, contacts ideally should "make", then "wipe" about .015 of an inch--UNLESS the "crossbar type", which should "just make, firmly"--no wipe.
Ron Rich

Emory Paper doesn't contain "sand".
1000 grit is like using a burnishing tool.

Ron's rule of thumb is not to fix that which is not broken, so I hope he won't be annoyed by my asking him (or others) to confirm that:

If the switches make and break when they should, they should be left alone, even if they have gaps that do not correspond to those in the manual.

I follow the old school rule -- If it ain't broke don't fizzit !
If the gaps do not match the book, suspect that the book is incorrect first, especially if the item is functioning OK ??
(Might also want to visit the eye doc ?? ) Ron Rich