Drill-O-Matic - Drill arm not returning home

roothorick

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I'm gonna call Benchmark about this again, but I've already called them oh, about six times over the years we've had this pile of scrap, and they've been less than helpful. I don't know what else to try -- I've tried putting the carriage limit cards every which way, I've replaced the stepper controllers, the motors themselves, swapped out the mainboard at one point... it seems to work for a while, so I'll put it back online, come back later, drill arm is resting in the middle of the machine. Usually, near the button bar. I'm about ready to take it out back and introduce the bastard to some thermite. Is this even fixable?
 
When it is powered on and stuck, can you physically move the arm around without forcing it? When it is powered off can you move the arm around freely?
 
When it is powered on and stuck, can you physically move the arm around without forcing it? When it is powered off can you move the arm around freely?

It's not actually stuck. The arm still moves. When it's in the wrong place and you start a game you can move it up, and it'll grind against the top when you get there. After grinding against the top until it stops, you can then move all the way back down, even past where it originally stopped, all the way home. It appears to think it has returned home... but it hasn't.

A power cycle fixes it temporarily -- it returns home and grinds against that corner before returning to attract. Is this normal, or should it sense when the motors are no longer turning?
 
When I first turn mine on, it goes to the lower left corner and grinds for a bit and doesn't make any more grinding noises until next power on. I don't think mine makes the grinding noise when you go all the way up, I will test that when I visit mine later this week.


In the past, I found that if you go through the hassle of making sure everything is square and level with the moving parts it really cuts down on the grinding noise at startup. But it usually doesn't stay that way for long.

Could one of the optos that finds home be dirty or flaky? I think it uses the same optos for detecting a win.
 
I would definitely go with checking the optos, these beasts are not new anymore, and it's very likely that you have a dirty or broken opto/s. The "grinding" you hear at startup is normal for the machine. The drill should return to the lower left corner upon power-up, as this is home position for it. Based on what you're describing, I'd also check the wiring, both at the limit optos and on the drill assembly itself. Do you have a manual for the game? That should help. If you don't let me know, I think I still have one.
 
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