Checking your Bally EM for shorts.

[OldReno]

The Bally was designed to have only a case ground.  The only ground is from the green ground wire of your 120V plug to the case.
None of the circuits should connect with case, although some folks used to intentionally put shorts into the machine to prevent cheaters from manipulating the machine's circuitry.  Most commonly people would run a jumper from the 70 wire on the coin lockout coil to the case.  This would in essence put half a short into the machine, so that if a driller tried to cheat the machine by contacting a switch, then it would blow the fuse and blackout the machine or take out the 50V.
There are two ways to check for shorts, the mechanics way, and the safe way.
The safe way, is to unplug the machine, set your VOM for ohms, and with one lead to case, check the 70 wire on the door (coin lockout coil is a good spot), the 20 wire (any one of your 6V bulbs, and the 30 wire (coin in switch).  If you have a short, it will show low or zero ohms.  If you find a short, then start isolating it.
Remove the top unit.  Check again.  Remove the reel mech.  Check again.  Remove the hopper, and check again.  When the short disappears, then you have found the bad subunit, and somewhat isolated your problem.
Most often, 6V shorts are the result of one of your door light bulb sockets touching to case.  Move the tab away from case and it should disappear.
50V shorts are a little more picky, as often some switch somewhere is touching to case ground.
If you want a pristine machine, to factory specks, get out those shorts.
The mechanics way of finding shorts is a little more hairy, and if there is interest I will share with you how to do that.
Voms? We don't need no VOMS.  We got jumpers, we don't have to show you no stinking VOMs!

[OldReno]

Since no one has inquired on how mechanics quickly (and dirty) check for shorts, here it is.
With your pocket plain end screwdriver, remove the coin acceptor.  Behind it you will see the coil lockout coil, and one of its wires is a 70 (orange) wire.
Ground your screwdriver to case, and quickly 'rake' the 70 wire.  If you see sparks, then you have a short.
If there are no shorts, you should be able to hold it indefinitely with no ill effects.
Be aware that there is enough energy in the 50V system (70 wire) to melt a good chunk of a nickel if it falls behind your acceptor and shorts accross the lockout coil.
You can actually weld a small screwdriver to case if you're not quick enough with this test. Trust me on this....
To check 6V , just slide screwdriver along the 20 (blue) wire of any door bulb to case, and look for a small spark.
Once you have determined you have a short, remove hopper and try again.
Remove reels and try again.
Remove top unit and try again.
You should be able to isolate your short to a subunit, and if you can't then it's probably in the case.
Get rid of those shorts, they may shorten your machine's lifespan.

[OldReno]

BTW, the size of the spark indicates the severity of the short.

[OldReno]

Anybody found any shorts yet?

[Neonkiss]

I just found your post..... Does that count???

Thanks for the info as I will use it for a Bally side by side I have. Have an issue with the coin in lamps and found some wiring where someone had modified.
I hate it when you find a machine where someone has been monkeying around with the original wiring. I have never been able to locate a schematic for this machine so everything is a guess.

K+ for sharing your tips here and if you have more keep the coming.
 

[CVslots]

I have a  831 that I have isolated the short to the top unit. Now that I have it isolated to the top unit I can see that when I replaced the fuse and  coined up I can see a flash comming from the top box. I'll dig a little deeper tomorow.


Thanks,
Darrell

[OldReno]

@Darrell, take the 4 screws out of the shadow box, and you'll be able to drop it down and see where it is.
If it blew fuse AFTER taking a coin, then look for missing insulation on a switch end, like your End of Stroke switch for the odds unit.  Sounds fun, keep us appraised....
@Neon, you still got that side by side?

[Neonkiss]

@Neon, you still got that side by side?

Oh Yaaaaa,
That one will be a keeper.
Have it wrapped up and in storage for now. Will dig it out and check for shorts, but that will have to be a future project.

[SilverFerret]

Hi again,
I'm having 6v issues as it seems. My 873 blew the 6v fuse so bad that the glass broke in half. After struggling to get the other half of the fuse out, I remembered that you wrote a topic on issues with shorts (great job with these topics btw).
I got out my ohms meter and followed your suggestions but can't seem to find anything.
I alligator clipped the common of the ohms meter to the cabinet and checked the 20 wire at the door bulbs and for kicks checked the 30 and 70 wires also with no resulting measurement on the meter. I also checked the meter by touching cabinet to another part of the cabinet and saw measurement.
I've been having some issues leading up to this where my winner paid light stays on because the hopper doesn't reset sometimes. Could this be related somehow?
Scratching my incompetent head.
Any ideas?
Thanks, Jim

[OldReno]

Don't know if they're related or not, but let's find that short first.
Here's something to try:
Unplug your top unit, and pull out your hopper, and reel mech.
Also unplug your door- both connectors.
Put in a new fuse, and one by one plug these units back in to see which one blows the fuse.
If the fuse blows with all units unplugged, then you've got some kind of short to case I suspect.
Otherwise, determine which sub-unit is blowing the 6V, and then you at least have it narrowed down.
Then do your ohms check on that specific unit until you find the short.
If you find short on the door, then you will have to check those two bulbs which illuminate the coin tray.  Often the sockets of the bulbs will touch to ground and give you fits.  Make sure all bulb sockets do not touch cabinet, and also the soldered tabs on them.
Does it blow fuse when you pull the handle, or during pays, or just when it's setting there?
Keep at it, good job, sounds like you're doing just fine!
I still say it's more fun to work on them than play them....

[SilverFerret]

It's definitely in the feature unit. I had them all out as you suggested and put the reel unit in and fired it up, then the hopper and still all was fine but as soon as I powered up with the feature unit in, it blew the fuse.
Any suggestions on typical issues with the feature unit that might give me a place to start?
Thanks, Jim

[OldReno]

Look for anything amiss.  Some sets of switches have a paper insulator built in which keeps the circuits apart -- that is, keeps switches from touching other switches which they are not supposed to. If you're missing that paper insulator, that may cause problems.
Send pics if you can.
Look for switches touching case, or bulb sockets that may be touching what they shouldn't.
Your problem may not necessarily be in the 6V, so check your 50V all around up there for problems, too.
Did you take apart your odds unit, and that little spider wiper assembly?
Does the wiring look ok, or are there added on jumpers and stuff?
As I recall the 873 has a lot of stuff in the top unit.
Check all your switch positions, to be sure they all close and fully open when they should.
The odds unit and disk and switches can carry both 50V and 6V if I recall. If a 50V switch is inadvertently touching 6V that could cause that.
You're getting it narrowed down, which is the key to troubleshooting these things.
For giggles, step up your odds disc all the way, and then plug it back in.
Are there any add-ons to the top unit, or does it look stock?
Any jumpers run which are obvious retrofits?
Ohm your coils to see if any of them read to case.  (e.g., odds coils to odds disc frame.  Other coils to their frames, etc.)
One attaboy...!
BTW, it may not be in the odds unit (feature unit), but some circuit that goes through the odds unit.  But odds is the place to start.  That's where my money is.

[SilverFerret]

I don't know if this is what I'm supposed to do but I put the alligator clip on the feature unit frame and was testing ohms on the male end plugs that go into the females inside the case and didn't get any that give me a reading but when I tested the wires on the step up coil (I believe it's called) It show current flow.
Here's a pic of the unit and one of the coil I'm referring to:
I haven't seen anything that looks amiss but I'm not sure what it is supposed to look like exactley.
Thanks, Jim

[OldReno]

Great pics!
OK, look at the switches on the lower right front side of your top picture.  Do they touch to case when you slide in the top unit?
You might want to loosen the 2 screws and move those switches slightly to the left. Try putting a piece of paper between that switch end and the link that contacts it.  Also see if any of them short to case.
Also, in your coil picture -- is the tab of the coil hitting on that screw? You might loosen that nut and move the coil and assembly back away from it. You should have a little adjustment there. Or put some tape on it. Or carefully bend it away from the screw.
Since you get ohms on that coil, try tracing the red wire from it back to whatever switch controls it.  Ohm that switch out, and follow it along where it changes wire color again.  See if you still get continuity.
Clip lead to case and check all switches.  None of them should short.
Check metal case thoroughly and look for where any sparks may have shown up.
I'm thinkin' you're getting 50V to the 6V system up there somewheres.
Good job!!!!
Ain't this fun?
I'm guessing one of the switches which work off of your odds nylon gear stop-post are shorting, probably associated with that red wire coming from your coil.
If none of the above works, then take your time, and make it a project.  No wires or switches should ohm out to case. Be patient and check them all one by one, and note down which ones are problems.
Send a pic of the top box when you get time....

[SilverFerret]

I did find something amiss I think. The second contact from the top in the top picture was continually making contact when it looks to be a normally open switch and surprisingly the wire color leading to it is the same as the one on the coil that I referred to previously. Also it seems to have some carbon build up or heat blackening or something. You can see it in the pic although I cleaned it off a bit already. I bent the contact down just a bit and also checked continuity at the coil again and am not getting the same results that I had before and even when I purposely close that switch, I still don't see the same results as before. The leads on the coil are not touching that screw. I think it was an optical illusion from the camera shot.
I'm going to pop in another fuse and the feature unit and see if that did it.
I'll let you know... hold tight.
Thanks, Jim

[SilverFerret]

No luck.
Guess it's a project that'll have to wait a while. Working the next seven days, 14 hours wth travel time so no time for the next seven. I'll get back to you when I can get into it some more or if I see or think of something in regards to it.
Thanks so much for your help Reno,
Jim

[OldReno]

OK, that is a 3 contact switch.  The top two contacts normally make, and the 2nd and 3rd leaf only make when the coil is activated.
Always try to adjust the shorter switch, because if you do the middle one, it may mess up when it closes to the bottom.
The top two should not contact at all when the coil plate is pushed down, only the bottom two then (of the top 3)
I presume that is your odds step up relay...? Can't see the label.
Hope that makes sense.
Great job so far.
Always my pleasure to help out.
Have a good work week.  Talk later.

[OldReno]

Bump.
I'm trying to group some of my posts together in order to find them more easily.
Thanks