Centipede Wont Boot

msignor

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Hi Guys,

I am trying to get a Centipede upright working again. Monitor was just recapped and new flyback so that is working.

When I turn the machine on in test mode or play mode all I hear is crackling on the speaker and on the screen; random background colors showing up as well as random text characters appearing on the bottom of the screen. The 1P and 2P lights are lit up and thats it. Won't coin up or anything. I can take some pictures / video if you guys want.

Removed and reseated all the chips with no change.

Voltages looked OK on the mobo and AR2. +-22v came in at 25. 5v was at 4.7 and all the others were in spec as far as I can tell.

I have a big blue on order.. but do you guys have any ideas on where to start?

Thanks,

Matt
 
Thanks for the super fast reply.. I will up the 5v and post back any change.

Regarding the watchdog.. I am a total n00b for this type of testing - first board repair. I just read the "How to fix a PCB" thread. So I find the watchdog pin on the CPU and then use the probe to see if its flipping hi/lo or not? I assume I just need to look up the pinout for the 8088 or is it on another chip?
 
Ok - Well adjusted the voltage to 4.96 and that was as close as i could get without getting to 5.1v. My 22v is definitely at 25v and I am not sure on how to adjust that (if you can)..

I also was able to throw on the logic probe and the cpu is LOW and then I hear a click from the speaker, and then the cpu goes high and back to low. This alternates and happens ever 2-3 seconds.

Where do I go from here?
 
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A few things:

a) Re-seat the program EPROMs
b) Verify the contents of the program EPROMs with the relevant MAME set
c) Check that the sockets are good for the above,
d) Re-seat the 6502 CPU and check socket

If that all fails, send it off for repair. :)
 
Your +5v is still low. It may not be the board at all but the power supply or ARII board.
 
I adjusted the voltage to 5.06v after a few tries.. Should I try moving it to 5.2v?

-- I removed and resocketed the ROM chips but not the CPU. I will verify continuity as well.
 
My 720 does similar things. Its losing a volt between the switcher to the PCB. As long as the 5V doesnt get too far above 5 on the pcb then you should be alright. I would slightly increase the voltage on the 5v and see if you can get the game to boot. I literally have to go up to 5.7 - 5.8 on the 5v line to get 720 to boot.

If your close to Monmouth County I have 2 centipedes here you could take readings on to compare.
 
Will give that a try - I was able to test the voltage at the CPU and it was the same as the test point.

Additionally, I tested the capacitence of some of the caps.. and one or two of the 1uf caps were reading 1.4 and some 10uf caps were reading 13uf or so.. could that have something to do with it as well?
 
Ok..When you remove and re-seat the roms and the CPU take you might need to clean the legs of the chips. Closely inspect the sockets as well there may be cold solder joints. And of course..you could have a bad CPU or bad Ram.

Additionally, I tested the capacitence of some of the caps.. and one or two of the 1uf caps were reading 1.4 and some 10uf caps were reading 13uf or so.. could that have something to do with it as well?

Those could be within tolerances..but you can always replace them.
 
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Replacing caps will not fix your problem and your voltage is fine at 5.1.Ii personally would not up it more than that.If you want you can go ahead and remove and clean the roms and cpu. Be very carefull you dont break any legs removing or cleaning them. At that point since centipede boards are known to have cheap sockets you can check each pin for continuity at the other side of the board. If that does not help you You can bypass the watchdog circuit and put it in test mode and see if you get any beeps. If that still does nothing for you the best advice i can give you is go back to the sticky on pcb repair and read it several times if you dont understand something google it. The best advice you can get on this board is on that sticky i go back to it constantly and according to the problem i have i learn something new every time. If at this point its over your head the best thing to do is contact Bitslicer he repairs these at a reasonable price. ,Luis
 
Ok - So. Bypassed watchdog and the system was the same.

Resocketed the CPU and there wsa also no change. I still am getting a LOW followed by HIGH then LOW again which to me seems like the watchdog is actually working as it should (being that I have the same result when bypassing it)

One thing to note is that when I took the board I hear an ever so slight crack which to my paranoid mind could very well be some chip that has its legs going through a cold solder joint.. Is the "creaking" considered normal?

Any other ideas on where to look next?

Thanks,

Matt
 
Any suggestions on who could repair it?

What would their process be to fix it most likely? Just follow the schematic and have all of the necessary replacement parts on hand ?? That would look like my biggest issue... just not having the right parts to repair..

This is a completely serials matching machine so I would like to use the original board if it all possible.

Thanks for all of the assistance thus far.

-Matt
 
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