(Topic ID: 127744)

Seeking switch matrix experts -- weird things happening

By Nokoro

8 years ago


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  • Latest reply 8 years ago by robertmee
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There are 96 posts in this topic. You are on page 1 of 2.
#1 8 years ago

I'm trying to diagnose a switch matrix issue on my Special Force. There are three targets that when closed trigger other switches. They are the R, O, and C in the ROCKET targets. When the R is closed, in game and in switch diagnostics, it triggers the B target in Bomb and the right coin door. If you look at the switch matrix, they are all in the same row. See picture.

Special Force Switch Matrix (1).pngSpecial Force Switch Matrix (1).png

I've circled the switch that I closed (in red) and showed the other two switches that register at the same time. Bomb "B" registers all the time when "R" is closed. Coin right sometimes registers. In game, the left bumper also sometimes registers, but rarely does this in switch test mode. A similar thing happens in switch test mode when I close Rocket "O", only this time Bomb "O" and Coin Left register as closed. So, essentially, move the circle and two arrows down one row but keep in the same columns. And, a similar thing happens when I close Rocket "C", one more row down.

A few other things to note. It doesn't matter if the trough switches are closed or open -- the same thing happens. No other switches are closed when this happens. If I close the Bomb switches (column with the right most green arrow), only that switch registers, not the others. Same with the coin door switches. So, it is only the Rocket "R", "O" and "C" switches that cause this problem, and the problem seems confined to their row.

At first, I thought it was a leaky diode, but looking at the matrix, I don't see how that could be given the symptoms.

Any ideas? Thanks in advance!

#2 8 years ago

If all of the switches are open it is unlikely to be the typical diode problem unless one of the caps is shorted or the cap lead is touching part of the switch.

Measure the voltage at each of the columns and see if there is any variance. The symptoms don't exactly match a locked on column, but it's still possible.

A logic probe would be better if you have one.

#3 8 years ago

Thanks. I'm a bit of a newbie at this. Can you tell me what you mean by locked on column and what measuring the voltage will show?

I was also wondering if it might be a short as the R, O and C targets are all in the same bank and they are the ones causing the problems in their respective columns on the matrix. I'll give them a visual inspection.

#4 8 years ago

I would check the switches wiring and terminals very closely and see if any terminals are touching when they shouldn't and for loose wires that may be touching or anything out of place or crap jumping terminals. Lightly touch the wires to make sure they actually are connected to where they actually go and then report back.

#5 8 years ago
Quoted from Nokoro:

Thanks. I'm a bit of a newbie at this. Can you tell me what you mean by locked on column and what measuring the voltage will show?

The column signals are pulsed. If the signal is locked on (or stuck high) it will cause symptoms similar to what you are seeing. The sequence of pulses is what tells the system which column has been triggered. If the column is always high then the game will think every switch in the column has been pulsed, which in one case matches your symptoms.

If the signal is high rather than pulsed, that column will read a higher voltage than the other columns. Again a logic probe is the preferred method of test, but a meter will give some indication of an issue.

The problem at the moment is that the symptoms are very inconsistent and conflicting to some degree. Some symptoms point at a column stuck high, some point at a diode problem and some point at a row problem.

So let's start with the columns and then move through the possibilities.

Have you worked on the game recently, either repair or installed led's?

Nice explanation of the problem, btw.

#6 8 years ago

Thanks for all of the responses. I checked all of the connections around the switches at issue, and they seem fine. I haven't at this point traced every wire through the machine but at least at the most problematic switches, the connections seem good.

I haven't worked on the machine for a while. This just started happening.

I did play around with it a bit more, and it seems to be getting a bit worse in that the problematic switches will now trigger most of the other switches in that column, some at different times than others. (By the way, when I say column, I mean row on the schematic listed above. I know that people just talk more in terms of columns with these matrices.) Also, the return lane switches, which are at the end of the second column (row) on the schematic will trigger most of the other switches in that column (row).

So, perhaps it is a high signal. To measure the voltage, can I do it anywhere along the column, or do I have to do it at one particular place? I don't have a logic probe. I'll try the multimeter and see what it says. If your suspicion is correct, terryb, and it is a column stuck on high (or in this case, three columns), what is the fix? Is this then a board problem?

Thanks!

#7 8 years ago

I chased the same problem for a month thinking it was something touching or bad diodes. In my case though I was working on the pin unsoldering a diode when I received a spark,(even though the game was off.) I blew my resistor array just above the pins for the switches on the mpu. Just throwing it out there. I found the problem was on the board when I swapped in another mpu.
https://pinside.com/pinball/forum/topic/jurassic-park-help-needed/page/2#post-2439438

#8 8 years ago
Quoted from Nokoro:

To measure the voltage, can I do it anywhere along the column, or do I have to do it at one particular place?

Do you have a better image of the switch matrix and I'll point out where to test. From what I can see it looks like the rows and columns are laid out differently than wpc (for example), but I can't read enough to tell.

Quoted from Nokoro:

Is this then a board problem?

Yes.

#9 8 years ago
Quoted from terryb:

Do you have a better image of the switch matrix and I'll point out where to test. From what I can see it looks like the rows and columns are laid out differently than wpc (for example), but I can't read enough to tell.

Let's try this one. Hopefully, this is better.

And, thanks again for the help. If it is a board problem, this will be interesting for me. These things used to terrify me, but now that this isn't my one and only pin, I'm feeling more brave. Will still have to decide whether to attempt it myself or send it out, though. But, first things first . . . got to track down the problem.

SpecialForceSwitchMatrix(2).JPGSpecialForceSwitchMatrix(2).JPG
#10 8 years ago
Quoted from Crispin:

I chased the same problem for a month thinking it was something touching or bad diodes. In my case though I was working on the pin unsoldering a diode when I received a spark,(even though the game was off.)

Yeah, this just started happening. My first thought was that a diode just went, but looking at the matrix, that isn't looking likely. I agree that I may be chasing this for a while. Oh well, at least if I hopefully fix it, I'll have that satisfying feeling at the end.

#11 8 years ago

The next thing to look at is the schematic that shows the order in which the switches are actually wired. The matrix shows you how they are all connected but the wire could be run from the coin door to the rocket to the aux captive switch in the machine itself.

I would probably work from the last switch in the actual order for the row to the first. In test mode trigger each switch to see if it triggers others. If it does not, go to the next.

If all of the switches trigger others in the row you probably have a board level issue.

If you find that there is a point in the chain where the ones you tested before it do not and after it do, start looking closely at that switch to see if the issue is there.

#12 8 years ago

Well, I just tried something to see if this problem was bigger than those first three rows. I discovered that closing the left slingshot and right slingshots, separately, trigger multiple switches in their rows, the 4th and 5th rows down respectively.

#13 8 years ago
Quoted from WonkoTSane:

The next thing to look at is the schematic that shows the order in which the switches are actually wired. The matrix shows you how they are all connected but the wire could be run from the coin door to the rocket to the aux captive switch in the machine itself.
I would probably work from the last switch in the actual order for the row to the first. In test mode trigger each switch to see if it triggers others. If it does not, go to the next.
If all of the switches trigger others in the row you probably have a board level issue.
If you find that there is a point in the chain where the ones you tested before it do not and after it do, start looking closely at that switch to see if the issue is there.

That's a good thought, since it does only seem to be some of the switches that trigger others. However, now that it appears that this is happening in at least 5 rows (perhaps more), could this really be a single switch or short issue?

#14 8 years ago

OK, let's change our terminology to send (normally called column) and receive lines (normally called row). The send lines are on the left and the receive lines are at the bottom.

Now that I can see the matrix better (plus the additional symptoms you've spotted) I'm suspecting it is a receive (row) problem.

Remove CJ4 and jumper from pin 10 to pin 13 and see which switches indicate closed. This will narrow it down to a board or playfield problem, although it really looks like a board problem at this point.

#15 8 years ago

Thanks. I'll try that and report back. Might be a day or two given work tomorrow. Really appreciate the help.

#16 8 years ago

Hey terryb, can you give me a little more description of what you are thinking? Here is a picture inside my backbox of the relevant area:

BackBoxCPU.JPGBackBoxCPU.JPG

I see J4 and can remove that. What do you mean by "jumper from pin 10 to pin 13"? Do you mean physically connect them, like with alligator clips? Are the pins labeled? This makes me a little nervous, so I want to make sure I understand exactly what you are saying.

Also, what is this test designed to do? It helps me if I know the reasons for these things. Thanks!

#17 8 years ago
Quoted from Nokoro:

I see J4 and can remove that. What do you mean by "jumper from pin 10 to pin 13"? Do you mean physically connect them, like with alligator clips? Are the pins labeled? This makes me a little nervous, so I want to make sure I understand exactly what you are saying.
Also, what is this test designed to do? It helps me if I know the reasons for these things. Thanks!

No problem, best to be careful when jumpering things. Pin 1 should be labeled on the board. Yes I mean physically connect the two pins with a jumper. Just jumper it for a couple of seconds and you should see the switch closure indications.

By jumpering from pins 10 to 13 we are simulating the closure of the Rocket R switch. If you look at the matrix you will see pin 10 goes to one side of the switch and pin 13 to the other side of the switch.

If you get multiple switch closures then we know the problem is on the board since we've bypassed all of the playfield wiring.

#18 8 years ago

Ah, I get it. Good explanation. Ok, I'll try and report back. May take a couple of days again.

#19 8 years ago

Well, I removed J4 and jumpered 10 and 13. It was a little hard getting the jumpers to touch just those pins and not others. When I did, I got "R" registering, and only R. I occasionally got coins right and bumper left, but if you look at the matrix, I think that was because the alligator clip was touching those other pins. If I held it steady, again I just got "R".

I then plugged J4 back in and had the problems again of hitting "R" and getting both "R" and bomb "B" to register.

I'm not totally convinced yet and want to try this again to get more data and make sure the results hold up. One problem is that every time the pin is on for a while, and then I shut it off, I have to wait 20 minutes or so to turn it back on for it to work. Old pins, I guess.

Anyway, if the results hold, I'm guessing this doesn't look like a board problem. Could something be wrong within the J4 connector itself, I wonder?

#20 8 years ago

From reading your explanations, it does not sound like a board problem...

If you want to rule out your board, expand upon the test you did above. Don't use alligator clips...too big. Get a paper clip and unfold it.

So, what you are going to do is test the entire matrix. Remove CJ4 as before. The rows and columns are two sets of pins: 1,11,12,13,14,15 and 2,3,4,6,7,8,9,10.

Go into switch test mode and start with your paper clip on pin 1. Then touch pin 2, 3, 4, 6, 7, 8, 9 and 10. You should register only one switch for each touch. Then move clip to pin 11 and repeat 2, 3, 4, 6, 7, 8, 9. Then pin 12 and so forth. This checks each possible row/column combination.

If one switch and one switch only reports then start the box method of diagnosing the PF to find the faulty switch/diode.

Follow this video and method: https://www.youtube.com/embed/ZgSyTmyZAxM?autoplay=1&rel=0

PS...you can hold the clip with your fingers on the pins...not going to shock you as you're only working with TTL level signals (5V).

#21 8 years ago

Hey, thanks for the paperclip trick. Though, I have to say, even holding a paperclip on the tiny ends of pins while trying to watch the results is quite difficult. So, I tried a number of the combinations again, including those that corresponded to the problematic switches, and each time, I got a clear indication of just one switch registering -- the correct switch for the pin combo. So, for example, Rocket "R" just triggered Rocket "R", and Rocket "O" just triggered Rocket "O"; no others. This seems to rule out a board problem. (I didn't have the stamina to try every single combination.)

I did watch the video of diagnosing a faulty diode when I first encountered this problem. I didn't realize that the video was by terryb who is helping me in this thread. Anyway, I don't think I can use that method as all of the phantom hits are in the same send row. In other words, they don't form a box. I'm really stumped. Would a short cause this type of problem, and cause it in each individual send row? Could it be something else? For example, I know these old Bally's have a solenoid expander that relies on a 555 bulb. If the bulb goes out, random solenoids will fire at the wrong time. Could it be something like that?

#22 8 years ago

The box is formed by some other switch that is normally closed. It's important to identify which switches are already closed due to balls in the trough, etc.

Do, this...take all the balls out, open the coin door, etc....do everything so that NO switch is registered in switch test. Be sure you are in the switch state test not switch edge test. I don't know what this particular machine calls it, but its the test that shows the current state of switches, not just a rising edge transition of a switch being made. Once you have no switches reporting closed, then close your rocket R switch. I'll bet that in this setup, only that switch registers. Now start closing some of the other switches that stay normally closed (coin door, ball trough, etc.). At some point your other row switches are going to register, I'll bet.

#23 8 years ago

Thanks, but I did try that at the beginning. I took all of the balls out. No switches were registering in switch test mode. I then hit the "R" switch and other switches in that send row registered. I tried hitting other switches in other send rows, like the rocket "O" switch and similarly got other switches in that corresponding send row to register. However, at no time do they form a box. Each time, the closed switches only correspond to a single row. That is what is so confusing about this. Unless there is something I am overlooking, I don't see how it can be a faulty diode.

#24 8 years ago

This is really odd. It's not the board based on your tests and it doesn't sound like the typical "box" type problem, unless one of the caps is shorted, but then that should show up a a closed switch. I'm thinking out loud here.

Check each of the send (column) wires at the connector for a short to ground. I'm not sure that could cause these symptoms, but it's worth checking. Also check the receive lines at the connector for a short.

If you could pick up a logic probe there are some other tests we can do. I can walk you through using the logic probe.

http://www.amazon.com/Elenco-Electronics-LP-560-Logic-Probe/dp/B000Z9HAP4/ref=sr_1_1

#25 8 years ago

The only plausible explanation is that you've got a short in one of the holding caps across the switches. That's the only other path if you are sure all switches are open.

I hate to beat this point into the ground, but are you SURE you are doing switch closed test not switch edge test in the diagnostics? I believe the display will report "ALL SWITCHES OPEN" in the correct mode. Sorry, not too familiar with the older Bally's so not even sure it has a switch edge test...but I've been down this road before with someone only to find out they were in edge test the whole time.

#26 8 years ago

I think terry and I are on the same page....It's a stumper. For further clarification, when you hit the "R" switch, then the coins Right and Bumper Left switches also show? What happens if you hit the coins Right or Bumper left switch?

#27 8 years ago
Quoted from terryb:

Check each of the send (column) wires at the connector for a short to ground. I'm not sure that could cause these symptoms, but it's worth checking. Also check the receive lines at the connector for a short.

Let me start with this before I buy a logic probe, but I don't mind buying one if necessary. Remembering that I'm new at this, are you talking about checking the wires on the female J4 connector? How do I use my multimeter to check for a short to ground? Thanks again!

#28 8 years ago
Quoted from robertmee:

I think terry and I are on the same page....It's a stumper. For further clarification, when you hit the "R" switch, then the coins Right and Bumper Left switches also show? What happens if you hit the coins Right or Bumper left switch?

Hitting coins right or bumper left doesn't do anything if I recall correctly (other than trigger those individual switches). That's what's weird. Only some switches do this. It seems to be the rocket "R" "O" and "C" switches that trigger others. And, the return lane switches also do this, as well as the slingshots. So, for instance, rocket "R" will almost always trigger bomb "B" and some of the others in that row. But, bomb "B" won't trigger anything but itself. And, always, the phantom switches are confined to the same row as the switch you are closing.

#29 8 years ago
Quoted from robertmee:

I hate to beat this point into the ground, but are you SURE you are doing switch closed test not switch edge test in the diagnostics? I believe the display will report "ALL SWITCHES OPEN" in the correct mode. Sorry, not too familiar with the older Bally's so not even sure it has a switch edge test...but I've been down this road before with someone only to find out they were in edge test the whole time.

Sorry. Forgot to answer this. I'm not familiar with a switch edge test. I think I only have a switch closed test. In any case, the display reports "all switches open" until I start triggering them, and then it tells me which are closed.

#30 8 years ago
Quoted from robertmee:

I think terry and I are on the same page....It's a stumper.

Yes it is. Especially the part where the number of false indications will fluctuate each time the test is done.

Quoted from Nokoro:

Remembering that I'm new at this, are you talking about checking the wires on the female J4 connector? How do I use my multimeter to check for a short to ground? Thanks again!

Game off, meter set to diode/continuity and check from each column wire to ground and each row wire to ground. Yes at CJ4, pull the plug and test.

#31 8 years ago

Massive thumbs up for Robert and Terry following this through.

#32 8 years ago
Quoted from terryb:

Game off, meter set to diode/continuity and check from each column wire to ground and each row wire to ground. Yes at CJ4, pull the plug and test.

So, I put one probe in the female connector on CJ4 and another probe on the ground braid, right? No connectivity would be a good thing, right? Connectivity would indicate that something is wrong, like a short?

For what it's worth, this is a great learning experience for me!

#33 8 years ago
Quoted from TimeBandit:

Massive thumbs up for Robert and Terry following this through.

Ditto that! I'm extremely grateful, and learning more in a week about the switch matrix than I have learned all last year!

#34 8 years ago
Quoted from Nokoro:

So, I put one probe in the female connector on CJ4 and another probe on the ground braid, right? No connectivity would be a good thing, right? Connectivity would indicate that something is wrong, like a short?

Connectivity would be a bad thing.

The switch matrix will either make you a better man or break you. In spite of that I'm sad to see it go away on Spike.

#35 8 years ago

No short to ground on the connectors on CJ4. I'll see if my friend has a logic probe. If not, I'll probably get one. Any other ideas in the meantime?

#36 8 years ago

Any possibility of posting a video that shows the switch "R" behavior? Video pointing at the score display and narrate to where you are hitting the "R" switch. Then maybe do a couple of others that are exhibiting the same behavior. Sometimes things get lost in verbal translation and a picture is worth a 1000 words

#37 8 years ago
Quoted from robertmee:

The only plausible explanation is that you've got a short in one of the holding caps across the switches. That's the only other path if you are sure all switches are open.

We're kind of left with Robert's suggestion about the caps--not much else under the playfield. I would think a shorted cap would show up as a closed switch, but I could be wrong. Just test across the caps for a short as you did before.

#38 8 years ago
Quoted from terryb:

I would think a shorted cap would show up as a closed switch, but I could be wrong.

I figured that too, but I'm scratching my head over what else it could be....I'm not greatly familiar with this era of Bally...I assume the caps are just radials with no polarity? They aren't electrolytic and polarized are they?

#39 8 years ago
Quoted from terryb:

We're kind of left with Robert's suggestion about the caps--not much else under the playfield. I would think a shorted cap would show up as a closed switch, but I could be wrong. Just test across the caps for a short as you did before.

So I should put one end of the probe on either side of the cap, is that right? Can I do this inline? Wouldn't there be continuity on the caps? How would a shorted cap read on the multimeter? What should I look for?

Also, and forgive my probably ignorant question, but could this be caused by a cap holding and releasing a charge over too long a period? My question may make no sense. I know the last time I had a bad cap, it caused a switch to fire randomly, but it was always just that one switch so it was pretty easy to identify.

#40 8 years ago

Also, terry, isn't the Bally switch matrix drawn rotated by conventional terms? I'm used to the column drivers entering on the switch side then to the blocking side of the diode. The way the drawing is, the columns are actually shown as "rows" which could be confusing the OP. So the collect weapons, right coin, and "R" are the same COLUMN, not the same ROW in regards to the switch matrix diagnostics. So, when the "R" switch is closed, multiple switches are showing up in the same COLUMN (although it would appear ROW from the way the drawing is done). Which to me makes sense, meaning on that column pulse of the "R" switch, there are return paths to three rows making the switch. And since that also happens on Column two with the "O" switch, it makes me think that three rows are shorted together somehow in the PF. When you pull the connector and test the matrix with the jumper, those shorts go away.

OP, can you pull the connector and using a meter, check for continuity between pins 12, 13 and 14 on the connector to the PF (not pins on board). If you have any continuity, you've found the source of your problem.

Again, a paperclip is your friend here...get a couple of them and stick them in the connector so you can get your meter leads on them. If it were me, I'd check every column to every other column and every row to every other row. That will narrow down where the short is. It's tedious, but so is guessing.

#41 8 years ago
Quoted from robertmee:

Also, terry, isn't the Bally switch matrix drawn rotated by conventional terms?

Yes, and the layout on the matrix is not helping at all. I've found myself getting confused a couple of times because of it, and have tried to call them send and receive instead of row and column.

Quoted from robertmee:

OP, can you pull the connector and using a meter, check for continuity between pins 12, 13 and 14 on the connector to the PF (not pins on board). If you have any continuity, you've found the source of your problem.

Good idea Robert.

Quoted from robertmee:

They aren't electrolytic and polarized are they?

Just radials. I think they should be checked as you suggested though, at this point we're looking for anything to provide some direction.

Quoted from Nokoro:

So I should put one end of the probe on either side of the cap, is that right? Can I do this inline? Wouldn't there be continuity on the caps? How would a shorted cap read on the multimeter? What should I look for?

One lead on each side. Inline is fine as long as the switch is open. When you first put the lead on the cap it should read low and then increase. If it's shorted you will just get a low reading just like you would checking a wire.

#42 8 years ago

Ok. I will try all of the above. I found I can touch the top of the connector instead of trying to put the leads into the holes. They aren't big enough and neither are my paper clips. Thanks guys! Will report back.

#43 8 years ago

In my experience, false positive on a row or column almost always point to a short to ground on the offending row or column at or near one of the switches in the group that is misbehaving.

#44 8 years ago
Quoted from robertmee:

OP, can you pull the connector and using a meter, check for continuity between pins 12, 13 and 14 on the connector to the PF (not pins on board). If you have any continuity, you've found the source of your problem.

Ok, I've done this and found no connectivity. I haven't yet tested all of the caps but will do so when I have a little more time.

Quoted from SadSack:

In my experience, false positive on a row or column almost always point to a short to ground on the offending row or column at or near one of the switches in the group that is misbehaving.

Yes, but would it cause an issue in almost all (if not all) of the sending rows?

Let's make sure I'm testing for a short to ground properly. When I checked off of the connector, I stuck one of the leads on multimeter to the ground braid and the other on the connector. Does it matter which section or piece of the ground braid I choose? Is it all connected?

Quoted from robertmee:

Any possibility of posting a video that shows the switch "R" behavior? Video pointing at the score display and narrate to where you are hitting the "R" switch. Then maybe do a couple of others that are exhibiting the same behavior. Sometimes things get lost in verbal translation and a picture is worth a 1000 words

I'll certainly do this when I have a bit more time.

#45 8 years ago
Quoted from Nokoro:

When I checked off of the connector, I stuck one of the leads on multimeter to the ground braid and the other on the connector. Does it matter which section or piece of the ground braid I choose? Is it all connected?

Should be good, but I would double check by testing from the ground braid to a ground on one of the boards. You never know if someone has disconnected part of the ground braid. As a general rule I always make sure I've got a good reading before moving on to a questionable reading.

#46 8 years ago

Is the diagnostic keypad hooked up in your game? It shares a lot of the same switches as those in the game. I'm not sure how it is wired up, but maybe it could be the culprit?

#47 8 years ago
Quoted from winteriscoming:

Is the diagnostic keypad hooked up in your game? It shares a lot of the same switches as those in the game. I'm not sure how it is wired up, but maybe it could be the culprit?

Yes, it is hooked up and seems to be working on its own. I'm not sure how to test it other than by virtue of the fact that it is allowing me to do the tests.

#48 8 years ago
Quoted from terryb:

Should be good, but I would double check by testing from the ground braid to a ground on one of the boards. You never know if someone has disconnected part of the ground braid. As a general rule I always make sure I've got a good reading before moving on to a questionable reading.

Thanks, but how do I identify the ground on the boards? (Sorry for all of the newbie questions.)

#49 8 years ago

Most boards (except Gottlieb) use the metal backplane of the backbox and the mounting screw holes of the board itself...If that's the case you would see a large trace around the perimeter of the board that encompasses the mounting screw holes.

Back to the continuity tests...

Please test for continuity between each combo of pins:

1,11,12,13,14,15...so put meter on pin 1, then 11, 12, 13, 14, 15. Then move to pin 11, and check 1, 12, 13, 14, 15 and so on.

and then 2,3,4,6,7,8,9,10...so put meter on in 2, then 3, 4, 6, 7, 8, 9, 10. Then move to pin 3, and check 2, 4, 6, 7, 8, 9, 10 and so on.

Make sure you're continuity is working by touching your two meter leads...I know sometimes I'm asking basic stuff, but a non-working meter has tripped us up before on these types of threads.

If you can get to the pins, you should be able to run through these in 5 mins or less and it could tell us alot. If you don't get any continuity, then close the "R" switch and repeat to see if that changes anything.

#50 8 years ago
Quoted from Nokoro:

Thanks, but how do I identify the ground on the boards? (Sorry for all of the newbie questions.)

No problem. I'm not sure if the bally boards have test points, but that would be the first place I would look for a ground. If not check the schematics, there will be ground on most of the connectors.

Robert beat me to it, and his answer was much better.

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