Defender coin door, what does this do?

YeastLord

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What is the coin door switch supposed to do? I can't figure out it's purpose and it's impacting the image on my monitor. (which seems insane)
I don't see any mention of it's purpose in the manual. It's totally possible I missed it.
It couldn't be a power circuit killer like the one on the back door so I'm at a loss.

As always thanks for the knowledge and help.
 

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Yes, it's an interlock switch. I believe for pins it cuts some of the higher voltage(s) under the playfield when the door is open (as opposed to killing the whole cab, like they do on arcade cabs). But for a Defender it should be wired to kill the whole cab.
 
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that's actually the memory protect interlock switch. you can't save to the high range of the CMOS with it closed.

it's wired to the same small plug on the power supply board for the GIs and coin door ground, and runs to the MPU via the plug with the single red wire. leaving that unplugged is apparently the same as always having the coin door open.

alternatively if you're using a switcher then the coin door interlock will not be connected to anything, same scenario as leaving the MPU connector unplugged.
 
Hey George, thanks for shedding some light here.

So what is the purpose of disabling memory when the door is open?

And you can't write to CMOS with the switch *closed*? I would think it would be the other way around (or what am I missing)?
 
The door open switch allow writing to the upper memory area where the game settings are stored. If you were to have a power glitch and the processor jumped to the game settings screen, a customer might be able to change the settings.

For home use, I recommend simply disconnecting the four pin connector from the main board so you don't have to deal with it.
 
Ah, ok. I get it now. Because you only ever change the settings on a Defender with the door open. That makes sense.

Thanks for the explanation.
 
it's functionally identical to how their pinball machines do it too. if you had a way around to accessing the service panel with the door closed it would kind of just endlessly skip and not let you change anything. :)

the Defender at work gets stuck in bookkeeping for this reason. the chip that controls the logic function of the door open/closed is bad, so I have to run a jumper to trick it into thinking it's open. I outline how to do it in my guide but at the time I typed that up I didn't understand why I had to do it. now I do. :p
 
This makes sense. Thanks guys. What I'm missing is how there is any way for this to impact my monitor image.

I'm just not seeing it.
 
My monitor image is way too light and a bit wavy. Not sync issue wavy, more like bad signal wavy.
However when I press the door switch the image get's darker and the signal improves.
The image used to be perfect until I started poking around the coin door and found the coin up wires.

Does this make any sense to you?
 
OK, I'm starting to think this is a ground issue. I took of the CP, checking and put it back and the monitor worked. I noticed that the joystick wasn't working correctly. It would only go up. The paper separator had fallen out so it was making contact non-stop.
I fixed that issue and now the monitor is cranky again.
I'm going to go over all the wiring and see if I can find the issue.
 
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