(Topic ID: 253437)

Flash Gordon Switch Matrix issue -- need some expert help

By Nokoro

4 years ago


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  • 19 posts
  • 6 Pinsiders participating
  • Latest reply 4 years ago by Quench
  • Topic is favorited by 2 Pinsiders

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#1 4 years ago

Hi all. I really could use the help of those of you who are switch matrix experts (and even those who aren't but still get by). Sorry in advance for the long post, but this one has me baffled. It presents as a shorted diode, but all diodes have recently been replaced, and the ones I've tested so far appear good.

The issue is this, when two switches are closed in the matrix, and you touch a third switch, a fourth switch will register. This is always in a rectangle on the matrix. This is why I had thought it could be a shorted diode. I watched terryb excellent YouTube video. I am posting a clean copy of the switch matrix, and a copy that I marked up with rectangles. Each rectangle represents an instance of where I have closed two switches, closed a third, and had a fourth register. For example, if Drop Target "C" and Drop Target "D" are closed, and I push on the right slingshot, the left slingshot (and not the right) will fire.

All rectangles have Drop Target "C" in common as one of the corners. I checked and replaced the diode to that drop target, but the issue continues.

I am in the process of tracing the wire off of the drop target to ensure it is intact and not shorting somewhere. So far, it looks good, but I haven't finished tracing it yet.

I checked the MPU by removing J2 and jumping the columns and rows, and all switches register as they should in switch test mode.

I have checked all of the diodes in some of the rectangles, but I have not checked all diodes in all rectangles yet. Though, the previous owner reports that he replaced them all when trying to diagnose this issue himself.

Is there something obvious I'm missing? All help is very much appreciated. I would very much like to get this great game running 100% Thanks!

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#2 4 years ago

Have you replaced the capacitors on all the switch matrix switches that use them? I'm talking about the 0.05uf ceramic caps located on certain switches such as "Top Target" located at the bottom-center on the switch matrix chart.

#3 4 years ago

I haven’t replaced the caps. But whenever I’ve had a cap problem in the past it has manifested itself differently. No switches register closed in switch test mode which has typically happened to me in the past with a bad cap. Do you really think a cap would cause these symptoms with the rectangles?

#4 4 years ago
Quoted from Nokoro:

I haven’t replaced the caps. But whenever I’ve had a cap problem in the past it has manifested itself differently. No switches register closed in switch test mode which has typically happened to me in the past with a bad cap. Do you really think a cap would cause these symptoms with the rectangles?

Since somebody else has worked on this game, I would verify their work, especially polarity of the diodes. Eliminate the coin door as a potential problem. Start the game and unplug the coin door 24 pin connector. Of course you won't be able to go into self test but you can manually trigger some switches.

#5 4 years ago

I'm having trouble understanding. C&D targets are down and hitting right slingshot fires the left? That would require a bad diode on the C target.
If you want to follow this through, to fire the left slingshot you have to travel from St4 to I3. The route takes you up through the right slingshot, backwards through the C target diode, then forwards through the D target.
However hitting the right slingshot should fire both slingshots.

#6 4 years ago
Quoted from Lovef2k:

Since somebody else has worked on this game, I would verify their work, especially polarity of the diodes. Eliminate the coin door as a potential problem. Start the game and unplug the coin door 24 pin connector. Of course you won't be able to go into self test but you can manually trigger some switches.

Thanks. I'll try.

Quoted from BigAl56:

I'm having trouble understanding. C&D targets are down and hitting right slingshot fires the left? That would require a bad diode on the C target.
If you want to follow this through, to fire the left slingshot you have to travel from St4 to I3. The route takes you up through the right slingshot, backwards through the C target diode, then forwards through the D target.
However hitting the right slingshot should fire both slingshots.

Yeah, that's the weird thing, but triggering the right slingshot when C and D are down only fires the left slingshot, not the right. I checked the C diode, and it is not shorted.

#7 4 years ago

Well, it’s not the coin door, but thanks for suggesting I check. I’m glad because it looks like a bit of a mess to figure out.

I noticed that the problem can be intermittent, but mostly there. For instance, I just turned on the machine and started a game. I dropped the C and D targets and hit the right sling, and the right sling fired correctly. I then hit the right sling again, and only the left sling fired. I then drained, got a new ball, dropped C and D, and then hit the right sling about four times in a row. Each time, the right sling fired correctly. I then drained, and on the next ball, after dropping C and D, the right sling triggered the left about 95% of the time, only occasionally working properly. Not sure what that means.

#8 4 years ago

So, it sounds like my next two steps are (1) check all diodes in the switch matrix, and (2) replace the caps.

For the diodes, am I right that I can test them without removing them as long as the switch is open?

For the caps, will a .047 uF work in place of a .05 uF?

#9 4 years ago
Quoted from Nokoro:

For the caps, will a .047 uF work in place of a .05 uF?

Yes

#10 4 years ago

I've now checked all of the diodes with the exception of the outhole and the lanes. The last owner put in microswitches, and those diodes are wrapped up, so I'm saving them for last.

Before I start replacing caps, I just keep coming back to the fact that the only common denominator is that every time the issue manifests itself, it makes a rectangle on the switch matrix that has drop target C as one of the corners. I just quadruple checked that drop target switch, and everything looks fine. Could the switch itself be shorted, somehow internally, even though everything external looks ok?

#11 4 years ago

I think I found the problem. Look carefully at the switch in the middle (which is switch C) compared to the other two. The other two have a light, yellowish-green piece of insulating paper between the two lugs, which also lies all the way down along the back contact. Don't see it on switch C. I just ordered a new switch. I'm really, really, really hoping this is the problem.

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#12 4 years ago
Quoted from Nokoro:

I think I found the problem. Look carefully at the switch in the middle (which is switch C) compared to the other two. The other two have a light, yellowish-green piece of insulating paper between the two lugs, which also lies all the way down along the back contact. Don't see it on switch C.

Indeed. Without the paper separator between the diode lugs, the diode is being shorted.

#13 4 years ago
Quoted from Quench:

Indeed. Without the paper separator between the diode lugs, the diode is being shorted.

Yep. My thinking exactly. Took me forever to find an issue with the switch. Wonder what happened to the paper?

#14 4 years ago

You can gently pry the layers of the switch apart with an exacto knife. You can then reassemble the switch properly.

#15 4 years ago
Quoted from BigAl56:

You can gently pry the layers of the switch apart with an exacto knife. You can then reassemble the switch properly.

Maybe I'll try that with the old switch when I swap it out just to have a spare. Do you need to use a particular type of paper for the insulation or would something like construction paper work?

#16 4 years ago
Quoted from Nokoro:

would something like construction paper work

Probably not for long.

"fish paper" is what's normally used as it's an electrically insulated material.
https://www.marcospecialties.com/control/keywordsearch?SEARCH_STRING=insulator+fishpaper+blade
Ignore the last three in the list.

#17 4 years ago
Quoted from Nokoro:

Maybe I'll try that with the old switch when I swap it out just to have a spare. Do you need to use a particular type of paper for the insulation or would something like construction paper work?

good catch! https://www.pinrestore.com/Supplies.html

#18 4 years ago

Got my replacement switch today, and that was in fact the problem. Thank you all for your help.

At some point, I'll get some fish paper and try to fix the old switch. How do you glue it all back together? Some super glue along the side?

#19 4 years ago
Quoted from Nokoro:

How do you glue it all back together? Some super glue along the side?

No glue, the end brown bakelite pieces are simply a tight fit on the two plastic tubes that hold it all together.
Glad you got it working!

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