(Topic ID: 292481)

Help please: MM: drawbridge-down switch kills castle gate switch

By JimSweet

17 days ago

Topic Stats

  • 10 posts
  • 3 Pinsiders participating
  • Latest reply 16 days ago by JimSweet
  • Topic is favorited by 1 Pinsider


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#1 17 days ago

I have a weird problem I've never seen before, and I hope someone can help me! This is for MM. When the drawbridge-down switch is closed, it kills the castle gate switch.

This has nothing to do with the mechanics of the drawbridge. I removed the linkage, so the motor doesn't actually move the drawbridge. There are two scenarios:

Scenario #1: I use the drawbridge test to put it in the neutral or up position. The drawbridge-down switch is open. In this case, the castle gate switch works fine. I can run my finger back and forth at the gate, and the switch toggles.

Scenario #2: I leave the motor right were it is (neutral or up). Then I manually close the drawbridge-down switch with my hand, and the castle gate switch no longer works. When that drawbridge-down switch is closed, the castle gate switch behaves as if the beam is blocked (i.e. dots off on the switch edges display).

It's easily repeatable back and forth. I let go of the drawbridge-down switch and the castle gate switch works. I close the drawbridge-down switch with my hand (without using the motor or moving the actual drawbridge), and the castle gate switch no longer works.

I went through and tested all of the other switches, and they all work normally.

The castle gate switch is on the same row as the drawbridge-down switch. The other switches on that row work fine whether or not the drawbridge-down switch is closed. Only the gate switch breaks. So, what's special about that switch? Well, it's the only opto on that row, if that makes any difference. And they are physically close, if that makes any difference. I thought they would share the same row wire right there by the switches, but since the gate is an opto, that row wire actually goes to the opto switch board, which is nowhere near the drawbridge-down switch.

Here's a vital clue: This all worked normally until I partly removed the drawbridge motor assembly, and took some other things apart around the front of the castle. After I did that, it was broken. So, clearly I did something around the area of the drawbridge motor assembly or the front of the castle that caused the problem. Initially, I figured I broke a wire, but I can't find anything broken. And now that I understand the symptoms a little better, I'm not sure how a broken wire would cause this. When I was trying to debug this, I replaced the optos themselves, and that made no difference.

To give you a little more background, the reason I started taking it apart in the first place was because my drawbridge gears are intermittently squeaking loudly when the motor spins. I was trying to take out the motor assembly so I could study the gears, but after getting it loose from the bottom, and disassembling the front of the castle, I realized that removing that motor assembly was more than I wanted to do. That's when I put everything back together and discovered the problem I had created with the castle gate switch. Independent of this switch issue, I still have the squeaking gear problem, but for now I'd be happy to just get the gate switch working again! I can play with squeaky gears, but I can't play with the castle gate switch broken whenever the drawbridge is down.

Does anyone know what could be wrong?

#2 17 days ago
Quoted from JimSweet:

I replaced the optos themselves, and that made no difference.

Tests - Switch Edge - do they work ? Does the correct opto switch register on the screen ?

First thought is switch matrix error - switch wired wrong, diode on backwards type stuff.

Switch wiring shorted to anything ? Switch lugs, pinched wire, anything ?

Next up, is a switch stuck closed and mucking up the row ?

LTG : )

#3 17 days ago

Had another thought. On that row. A switch mucked up internally where you can't see it. It closes, opens, yet internally still is closed.

LTG : )

#4 17 days ago

In switch edges, all switches work except the castle gate, and they work whether or not the drawbridge-down switch is closed. The castle gate switch registers fine on the screen in switch edges and behaves properly when the drawbridge-down switch is open. But when you close that switch (by hand without doing anything else), the castle gate dots go off in switch edges, and breaking the beam no longer registers (I guess because it is already stuck in the broken-beam state).

I looked for a switch stuck closed, and everything on that row works fine. I can toggle the switches and see the results on Switch Edges.

It had to be something I did when I was messing around with the drawbridge motor assembly, so that rules out things like diode in backwards (since I didn't remove/install any diodes). It could be something is shorted or broken, but for the life of me I can't figure out what it could be. I was hoping that these symptoms would ring a bell and be recognized as the behavior you get when a certain thing is wrong.)

You suggested a switch broken internally. I'm thinking no because each switch works perfectly when the drawbridge-down switch is open. So, if it was a bad switch itself, then I would expect it to be bad all the time.

Oh, and from the switch edges standpoint, the drawbridge-down switch seems to register open/closed as expected with one exception. When I'm in Switch Edges, and I close the drawbridge-down switch by hand, I get an abnormal double beep. I think it's registering both switches getting tripped. The drawbridge-down goes to closed, and the opto goes to open, simultaneously. During that double beep, it ends saying that the drawbridge-down is the last switch, but I think it flashes or an instant that the castle gate switch is also toggling.

#5 17 days ago
Quoted from LTG:

Tests - Switch Edge - do they work ? Does the correct opto switch register on the screen ?

Switch wiring shorted to anything ? Switch lugs, pinched wire, anything ?

LTG : )

Edited LTG's quote - this seems like the most likely scenario to me.

#6 16 days ago

Thanks for the replies! I really appreciate the help!!!

I'll spend some time today trying to look for something shorted or a pinched wire. It would be very helpful if someone with schematic-level knowledge of how the switch matrix works had a theory about exactly what wire might be shorted to what, in order to cause the drawbridge-down switch to kill the gate opto like that.

Or any theories about what causes that double beep when I close the drawbridge-down switch.

I'm hoping there's some electrical explanation for the behavior.

#7 16 days ago

TJ saved the day. He found it in about 5 minutes. On the drawbridge-down switch the white wire was soldered on the wrong side of the diode. I believe that meant that the switch was driving a hard high when the drawbridge-down column was not selected (i.e. at the time the castle gate column is selected). And that hard high overpowered the opto circuit that was trying to drive it low. Interestingly, it would be an issue for all the other switches on that row, too. But all the other switches are regular switches with solid ground connections when closed. And the hard high drive from the drawbridge-down switch wasn't strong enough to budge the solid ground. So, the other switches weren't bothered. Only the opto.

In any case, all of that makes sense now. The part that doesn't make sense is how it every worked before. I didn't change any soldered wires when I was screwing around with it, so it was like that before. But somehow it was working for some odd reason. Since the problem was a drive fight, previously the correct guy was winning, and then after I screwed around with it the wrong guy was winning. Mysterious.

However, the bottom line is that if you ever have a regular switch screwing up an opto switch's behavior, check the diode connection. Hats off to TJ.

#8 16 days ago
Quoted from JimSweet:

check the diode connection.

See post #2

LTG : )

#9 16 days ago

If you ever run into this again. Only a few minutes to check every switch in your game. They are all wired the same. White wire and black end of the diode to a lug, green wire to a lug, silver band end of diode to a lug.

LTG : )

#10 16 days ago

Yes, you were absolutely right with your diode tip!

It was my bad for only checking the diode for shorted or broken wires. I didn't check to see if things were soldered right, because I knew I hadn't soldered anything, and I was SO sure that I had broken it when I was messing around in there. It never occurred to me that it had been "broken" all along and it was just a matter of (mysteriously) having a new winner of the drive fight all of a sudden. It really never occurred to me. <sigh>

If I had more experience, I would have known how to FULLY follow your tip the way you intended, and the problem would have been fixed right away. Live and learn...

In any case, it was exactly what you said, and I really appreciate your help!

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