4 player Demolition Derby MCR III power question

cwales

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I picked up a 4 player Demolition Derby yesterday that was in a barn. It worked before we loaded it, it worked for a little bit when we got back to the store.. Now it's not booting and this LED circled in this picture is blinking on and off. The power seems to go on and off with the blinking.

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The battery was badly corroded but had not leaked onto the board yet, I just cut that off. I have not tried anything else other than reseating connectors to the power supply.

I can't seem to find any directions on testing an MCR III. Anyone know where they are some or anyone have any tips on what I should check?

Thanks.

EDIT: I realized i had the same power board in Crater Raider so I swapped it into there and it's fine. I'm now thinking maybe it's the Turbo Cheap Squeak board since that's where the led is blinking and the sound never worked right when it did work last night... I reseated all the chips and reflowed solder on it but there is no change.
 

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I can't seem to find a pinout for the "MCR III Dual Power Amp" to test voltages on there... There's power but I'm not sure what it should be at. It's got this funky adapter thing, is that normal?

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I just went and looked and mine and it does NOT have that connector coming that you show on the dual amp board.

mine looks just like yours but without that little go-between connector. I just got my boardset back from cdjump so I don't have my game together right now.
As soon as I get hte art from thisoldgame I will be doing a complete restore. Mine is a pile of shit, but I have rebuilt and rejuved the monitor to keep my self busy. I can imagine I have 100 hours of work to do on this bad boy, but it will look new.

nice pick up
 
Thanks for the input, that's interesting. I should movet the wires around an get rid or that thing.

I'd still like to know what the led blinking means, I can find posts where people talk about it blinking twice or three times but not over an over...
 
Casey, I am assuming that was the one up a couple days ago on Craigslist? If so, nice grab there. Steve showed me the ad a day after it went up. Good score.

How did you pick it up? That thing is a beast!!!
 
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I'm kinda confused by your post....does the machine now boot up and play after swapping the power supply? I believe mine has the same adaptor on the amp board.

-Mark
 
I'm kinda confused by your post....does the machine now boot up and play after swapping the power supply? I believe mine has the same adaptor on the amp board.

-Mark

No, it does the same thing. I just know the power board is good because I tried it in crater raider.
 
Casey, I am assuming that was the one up a couple days ago on Craigslist? If so, nice grab there. Steve showed me the ad a day after it was up, so he was late on that one.

How did you pick it up? That thing is a beast!!!

Yeah that's the one decent deal at $100. It was in a barn and a couple people there helped us load it up. Had to call for help to get it out and my back is still feeling it. The lady actually held it for me for three days, I thought I wasn't going to get it since there was no way on earth I could get up there sooner.
 
Cool score! I saw one at an auction once and almost won it too. I hadn't really played it before, but from what I remember seeing it looks pretty cool, especially for 4 players.
 
Nice score. It's a great 4-player game; put plenty of quarters into one when I was a kid.
 
it means it is rebooting. Normally, it would blink a set number of times, and go out. If its continuously blinking its getting so far along in the boot sequence, and then either resetting on its own, or being reset by the pcb. If the pcb is resetting itself, it'll cause the CS to reset as well, as they both share the same reset line.

You can unplug all of the connectors to the pcb and see if it blinks a set number of times and then goes out.

edit - and i don't have one here, but i'd guess that adapter between the harness and the amp pcb is an adapter that adapts it from a sound amp w/mixing to a plain old sound amp without mixing (or vice versa).
 
it means it is rebooting. Normally, it would blink a set number of times, and go out. If its continuously blinking its getting so far along in the boot sequence, and then either resetting on its own, or being reset by the pcb. If the pcb is resetting itself, it'll cause the CS to reset as well, as they both share the same reset line.

You can unplug all of the connectors to the pcb and see if it blinks a set number of times and then goes out.

edit - and i don't have one here, but i'd guess that adapter between the harness and the amp pcb is an adapter that adapts it from a sound amp w/mixing to a plain old sound amp without mixing (or vice versa).

That's excelent input, thanks much.

Edit: I had said it did the same thing with the pcb unplugged but I was missing one of the plugs that's on the other side... It does not reset with the pcb unplugged.

Here is a fun video of it resetting.

 
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Just verified with Casey that the main PCB itself is causing the resets. Could it be as simple as a bad ROM or CPU? I know Atari vectors will watchdog if the ROMs are bad so maybe?
 
Just verified with Casey that the main PCB itself is causing the resets. Could it be as simple as a bad ROM or CPU? I know Atari vectors will watchdog if the ROMs are bad so maybe?
could be, i'd give it about a 20% chance of it being the cpu or a bad rom.
 
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