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(Topic ID: 151069)

Can 90s B/W switch matrix wires break internally?


By mot

4 years ago



Topic Stats

  • 15 posts
  • 9 Pinsiders participating
  • Latest reply 4 years ago by barakandl
  • Topic is favorited by 2 Pinsiders

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#1 4 years ago

I'm reassembling a Johnny Mnemonic after a very thorough teardown and cleaning. I believe everything worked beforehand, but now I'm having problems with a switch matrix row. I know it's a problem with playfield wiring, but I'm certain that there are no disconnected wires on any switches.

Switch matrix row 4 has two cabinet switches (working) and five playfield switches. I've physically examined the connection of the white/yellow wire at each of these switches about a million times, and everything is perfect, however, I'm losing continuity (as measured with a multimeter) across one of these wires. I've examined the wire for breaks, kinks, or twists, but haven't found anything.

So basically, my question is this: can a switch matrix wire break internally, without any obvious signs of stress on the wire?

Switch 34: Trough Ball 3 (doesn't work, yellow/white wire terminates at opto board)
Switch 44: Left Jet Bumper (works, two yellow/white wires solidly connected)
Switch 54: Right Ramp Enter (doesn't work, two yellow/whites tied together on molex pin under playfield)
Switch 64: Left Jet Lane (works, two yellow/white wires solidly connected)
Switch 74: X Hand Encoder (not connected yet, two wires are solidly tied together on molex pin under the playfield)

#2 4 years ago

I've also Googled this, of course. The only precedent I found was this video, where someone claims to have had this problem with a Theatre of Magic. He cut into the wires to test for continuity and locate the problem wire. He ultimately fixed the problem with a jumper wire where he says he lost continuity.

#4 4 years ago

I've tested on the CPU board and was able to use a wire to get all of the switches to close properly.

I've also tested the trough opto. The emitter is good (verified with digital camera). The receiver doesn't trigger when using an incandescent flashlight (the other optos do). Additionally, I've manually used a jumper to test right on the switch matrix connections to the opto board, and while I can get other rows to trigger, row 4 won't. And of course that's the case, because it doesn't have continuity to the white/yellow wire on the working switches.

I'm 100% certain this is a playfield wiring problem.

#5 4 years ago

Yes, it can happen, particularly in cases where the wire gets snagged on something and gets stretched or yanked. If you truly believe a wire between two switches is broken unsolder both ends and check continuity while flexing and moving the wire - a meter with an audible continuity test setting helps here. Also follow the wire for its entire length and look for any possible damage or signs of stress to the insulation.

#6 4 years ago

It seems from games worked on before me the fix was a couple of big globs of solder. A few pieces of electrical tape and a piece of speaker wire to bypass.

#7 4 years ago

The wire is highly unlikely to go open internally. If it does, it is going to be from getting pinched, really twisted, or mangled pretty bad. Very likely if the wire is open, the insulation is also going to be damaged.

More likely cause is that a switch wire which is daisy chained all over a row/column broke loose. A lot of times two wires will be connected with solder at a switch lug. More likely to have a wire fall off one of these switch lugs than a wire to break internally for no good reason.

#8 4 years ago

or, there is a crimp conn for a split off in line and one side of the crimp has let go. both viable possibilities

#9 4 years ago

I've had exactly two wires break internally in the past 30 years.

#10 4 years ago

Run a jumper over a suspect wire and it's easy to check.

Can happen. Especially on wires that move with a mechanism or something.

LTG : )™

#11 4 years ago

Ive seen this happen on a number of games, including STTNG (cannons), CV (Ringmaster) and LOTR (Balrog) all mechanisms as LTG stated...I have also seen it on connector ends on WPC pins where the IDC cable connects to the cpu board, that would be a guess on this one, look at the switch matrix, find which wire it is and check the connector and do a continuity test !

#12 4 years ago

Thanks everyone for your help. Maybe wires can break internally, but not today!

My problem was a good old fashioned broken wire. Not at one of the switch lugs, as I checked those a million times. This one was mid-wire, hidden under the pop bumper. In fact, it looks like the pop bumper was rubbing against the wire and cut it over time.

The pop bumper was also obscuring the view of the wires underneath.

So, people of the future. If you think you've got a broken switch matrix wire, and you've narrowed down the color of the wire (I was right about that after all!), look around pop bumpers and moving mechanisms. That should have been obvious to me yesterday!

IMG_20160202_175233_(resized).jpg

#13 4 years ago
Quoted from JamesH007:

Ive seen this happen on a number of games, including STTNG (cannons), CV (Ringmaster) and LOTR (Balrog) all mechanisms as LTG stated...I have also seen it on connector ends on WPC pins where the IDC cable connects to the cpu board, that would be a guess on this one, look at the switch matrix, find which wire it is and check the connector and do a continuity test !

The ship in Pirates will also eat through wires, but the insulation also goes from the few games i have seen.

#14 4 years ago
Quoted from barakandl:

The ship in Pirates will also eat through wires, but the insulation also goes from the few games i have seen.

That's good info. I tagged POTC on this post.

#15 4 years ago

Un-shrunk Shrink tubing seems like a good way to help protect high wear wires. Even in the plastic wrap constant rubbing movement will eventually wear through wire.

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