Centipede Mini Freezes Up

Doodbird

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Donor 2012
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Hey guys, I picked up a beater mini cabinet cheap. When I first plug it up, shy of some monitor color adjustments, the game works fine. After it's plugged up (playing or not) for a while, it freezes up. Sometimes, it makes a buzzing noise when it freezes; other times, it just freezes. When this happens, the picture on the monitor is jumbled up. It doesn't look the same each time.

I have tried unplugging and re plugging the PCB, and this helps sometimes.

Any suggestions? I'm new to this stuff.
 
Could be many things.
First thing...
Put centipede in test mode to see if there is rom or ram errors
Second Clean connectors.
Third rebuild the power supply and replace big blue
If still happens then need to start looking at the board

Sounds like the CPU is running bad instructions or memory is corrupt
But watchdog should reset it which makes me think after being on a while some components are not working within spec which could be a powe issue or chips heating up and no longer working correctly

Brian
 
Could be many things.
First thing...
Put centipede in test mode to see if there is rom or ram errors
Second Clean connectors.
Third rebuild the power supply and replace big blue
If still happens then need to start looking at the board

Sounds like the CPU is running bad instructions or memory is corrupt
But watchdog should reset it which makes me think after being on a while some components are not working within spec which could be a powe issue or chips heating up and no longer working correctly

Brian

Thanks Brian.

I put it in test mode, but it was still acting crazy.

Next, I cleaned the connectors. No change.

I looked at the board, and say where the transistor at Q4 was bent down, and one of the three legs were broken. I tried to find what this guy did, but I had no luck. I pulled the PCB and got the numbers off of the transistor. When I had the board out, I reset all of the roms. I also straightened the transistor back up (one leg still broken).

Once I put the board back in, it played great. I left it up and running for a couple of hours, and it looked fine. I will be able to leave it on for longer on Thursday.

Can anyone tell me what's going on at Q4 on this board?

Thanks,
Miles
 
Can anyone tell me what's going on at Q4 on this board?

Q4 is part of the video output circuit. IIRC it is for the color green. Without seeing the schematics I would guess it is probably for color gain. You would still have color just not as bright. It should be a 2n3904 transistor.

Brian
 
when the system locks up, does resetting it (power on and off immediately) cause it to work again? once it locks up can you put it in test mode to see if any errors.

locking up after running for a while usually indicates some type of power failure or component failure due to temperature.. though that's not easy at all to troubleshoot unless you can reproduce it reliably.

On a good note if you want to replace the centipede board. I repair and sell them. let me know I have plenty of centipedes already fixed and ready to go (though I always retest and playtest before shipping out again, in my centipede cabinet) won't fix the problem if it's a power issue, but if it's a board issue that will fix it.

-brian
 
Before you go too hog wild, measure the +5 volt levels at the game board when you first turn it on. When it crashes, measure it again. Is it about the same or did it drastically change?
 
Thanks for the help guys. I will have time on Thursday evening to check on the machine again. Wednesdays are full for me at church. I may plug it up tonight, and then check on it in the morning.

I'll update my findings once I've allowed the game to play for several hours.

If the color is ok, and the game works fine, is it worth me replacing the transistor?

As I said, I'm new to games and their workings. I have a couple of cap projects on some beater monitors to hopefully bring my soldering skills back to near par. I don't want to start my training on a working Centipede board if you know what I mean.

Miles
 
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