(Topic ID: 237495)

Switch Troubleshooting


By chrismcb

11 months ago



Topic Stats

  • 11 posts
  • 5 Pinsiders participating
  • Latest reply 11 months ago by chrismcb
  • Topic is favorited by 1 Pinsider

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#1 11 months ago

On my Eight Ball Champ I've got 6 switches that aren't working. 4 on one strobe, 2 on another. I've tested the switches themselves, and they seem to be ok. Some of the switches on each strobe/return are working, so I'm guessing the connection to the board is ok. The continuity between the broken switches and the working switches seems fine. I replaced the all capacitors (except on the drop targets) and that didn't help.

What is my next step in troubleshooting? Is it possible it is the board?

It looks like H, A, P, left outlane, center rollover and the 6 drop target aren't working.
The first four on strobe 2, and the last two are on strobe 3.

#2 11 months ago

Have you replaced the 0.047uf ceramic capacitors on the various switch matrix switches that use them? The schematics show which switches have caps on them. I've seen a number of Eight Ball Champs lately that had switch issues and the caps were the solution a couple times. I would start there regardless, because they're most likely due for replacement anyway.

Edit: i see you already changed the caps, but you mention you didn't change them all. Personally i would track down the remaining caps and change them. I would double check that all wires and diodes are connected to all switches in the problem rows/columns--a light tug on each wire and diode to be sure they aren't hanging on by a thread. Re-flow the header pins for the switch matrix on the mpu and re-pin the female connector there too.

#3 11 months ago

It seems really strange that the in the 5x7 matrix of strobes/returns, you always have at least a couple of strobes and a couple of returns that work but others that don't. I don't even pretend to understand what happens in the chips and it very well could be a problem in one of those interpreting/transmitting the signals incorrectly.

When you say the switches work or not, are you using a DMM or the open/closed switch test from the Control Board? Testing continuity through a switch and transmitting a signal to the control board can be two different things. Do those two tests yield the same results?

Six problems without any commonality is hard to figure out, which is surely why you posed the question. You seem to know more about the craft of pinball repair than I do, but I would like to help brainstorm a possible fix if I can.

Do the wire codes match up for everything? We tend to assume that everything came out of Bally as it should have and nobody since has tried and failed miserably to hack through a problem on your machine. Plus, there is at least one confirmed error in the EBC manual that I am aware of. It is possible in my mind that you have one strobe that is dead and the wiring diagram for the switches in the manual is not correct. I (think I) can help you compare your machine to mine if you want.

#4 11 months ago

Guys thanks for the suggestions. newbieinkc, to answer your main question is the manual correct? Yeah, for the most part the manual is correct. At least for the strobes (its possible that the return lines aren't) as I tested the continuity between the switches in the manual on one strobe, and they were fine.

But, I got everything working. First of all, how did I test this? I put it into switch test mode. And depressed the switches by hand. The six I mentioned didn't work, in that they didn't show up on the display. After posting this, I decided to try it in a game setting. One reason this is different is that in switch test mode you need to depress the switch for several seconds (that is the game only tells you want switch is depressed like one a second or two) So I went into game mode, and the switches seemed to behave better (in contrast, a couple of weeks ago, the switches weren't working in game mode, and so I bought some capacitors. )

Anyways, the H only seemed to work if I held it down, while the other two (A and M) worked if I just quickly depressed the switch. The H originally had a capacitor, but I removed it. I had read elsewhere you should only have capacitors on the roll overs and other momentarily depressed switches. But since this switch seemed to work if I held it down, I decided to put a capacitor back on it.
While I had the playfield out, I decided to go ahead and replace the capacitors on the drop targets. These are hard to get to, which is why I skipped it earlier.

Finally I cleaned the switches on all the roll overs (as well as the H, A, and M) I probably should clean the outlanes as well.

Between replacing ALL of the capacitors, and cleaning the switches (and making sure the switches make contact when the rollover/trigger is depressed) I think I got everything working!

#5 11 months ago

Excellent!! Good work!

Those caps can fail a couple different ways and sometimes will affect other switches in the same rows/columns, so it's always smart to do all of them on these games. Enjoy your EBC!

#6 11 months ago

I'm glad you got everything working. Do you think it was the caps or the clean/adjust?

In my EBC, the stuck switch test would register a closed switch whether the capacitor was good/bad or gone. Switches with bad capacitors are more likely (logically) to test like a closed switch while it is open instead of vice versa. Working capacitors are not involved with closing the switch circuit, but rather giving the signal some "oomph" for the first few milliseconds after the switch gets closed. Blown capacitors can short, which would make the switch test closed, but if they blow "open", the switch should still theoretically work as normal but not so sensitive to brief closures.

The reason for my line of questioning is that with so many switches not working, you could have just had a dirty machine that needed adjustment and had some angry capacitors (as was the case with my auction-bought EBC, but not quite to the extent you experienced). Hopefully, you don't have a situation where a prior owner used sandpaper or a file to clean the switches and you won't have a bunch of problems once everything is tuned up.

#7 11 months ago
Quoted from newbieinKC:

I'm glad you got everything working. Do you think it was the caps or the clean/adjust?

I think, for the most part, it was the capacitors.
When I started trying to debug the issue, one of the first things I did was test the continuity across the closed switch. I did the for the outlanes, but not the two rollovers. The continuity was fine. Later I went back and did the same test with the rollovers, and they weren't fine.
In the process of cleaning the switches I bent them just enough, that the rollover didn't actually close the switch. I didn't even think of this issue when I first started debugging.

As far as the drop targets go, I've learned my lesson. Next time I'll replace the capacitors when I rebuild the drop targets. As it was it was a pain, trying to fix them insitu. I'm also just going to replace all the capacitors in the first place. When I first started on this machine, several sources said to just cut the capacitor. But recently I'm seeing several people saying you need them for the machine to work properly. So new capacitors it is.

#8 11 months ago

Just a curiosity question: Has anyone used a capacitance meter to measure the bad caps to verify they were bad? I just checked every cap on a Bally machine, and they all read anywhere from 45 to 60 nanofarads. (0.045 to 0.60 microfarads). Since the caps all read close enough, I did not change any. I'm in the middle of a rebuild, so I guess I will answer my own question when I get it back together. I know they're cheap, I could change them all while easily accessible, but I am not a believer of changing out working stuff with working stuff. I have found I usually introduce a new problem that didn't exist before, such as snagging a switch with the solder iron cord, etc.

#9 11 months ago
Quoted from chrismcb:

I think, for the most part, it was the capacitors.
When I started trying to debug the issue, one of the first things I did was test the continuity across the closed switch. I did the for the outlanes, but not the two rollovers. The continuity was fine. Later I went back and did the same test with the rollovers, and they weren't fine.
In the process of cleaning the switches I bent them just enough, that the rollover didn't actually close the switch. I didn't even think of this issue when I first started debugging.
As far as the drop targets go, I've learned my lesson. Next time I'll replace the capacitors when I rebuild the drop targets. As it was it was a pain, trying to fix them insitu. I'm also just going to replace all the capacitors in the first place. When I first started on this machine, several sources said to just cut the capacitor. But recently I'm seeing several people saying you need them for the machine to work properly. So new capacitors it is.

Drops don't need the caps. Their switches transition to closed and stay closed. The computer has no trouble detecting those closures. Only the switches with quick open-cosed-open toggles need the caps.

#10 11 months ago
Quoted from cody_chunn:

Drops don't need the caps. Their switches transition to closed and stay closed. The computer has no trouble detecting those closures. Only the switches with quick open-closed-open toggles need the caps.

I agree completely. I'm not 100% sure what the clock rate is for sensing switches in a 6803, but it is probably 60hz. The machine might not detect a very short momentary switch closure because it only "checks" for a very short period of time 60 (?) times a second. The capacitor adds amplitude and probably more importantly duration to the signal that the control board gets to indicate a closed switch.

The drops don't need caps, but the targets behind them will work more reliably with good caps. Lane rollovers can probably go without caps but rollover buttons will miss some hits if the caps are dead or missing.

#11 11 months ago
Quoted from cody_chunn:

Drops don't need the caps. Their switches transition to closed and stay closed. The computer has no trouble detecting those closures. Only the switches with quick open-cosed-open toggles need the caps.

It isn't the drop switch, but the back target switch. I can see the ball bouncing off the target fast enough to need the capacitor.

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