game resets after 5-10 min play

mfuson1

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Ok my fellow guru's, I picked up a martial champion by konami its jamma.. used to be a double dragon originally . After play about 5-10 min the game either goes into a rom check or goes into a (what icall a sleep mode). I tested the power supply BEFORE this happens and i have 5.8 volts at the +5 v and 012.8 volts on the 12v out of the power supply. AFTER it goes into (sleep mode) i have 0 at + 5 and 0 at 12v .. I was messing around with it today and took about 10 min and it went to reset checking rom screen and then the sreen was jumbbled (( from what ive read)bad z80) but tested the power supply and had the same reading 0 @ +5v and 0 @ 12 v... Is this a bad power supply ??? Thanks
 
It looks like your power supply is shutting down, possibly due to overheating. I think this is what you are referring to as 'sleep mode'. The power supplies are usually repairable and if not they are easily replaced.

However, I don't understand how you could still have a jumbled screen with no power to the board?
 
I didnt either thats why i said what happened today. idk
On your power supply you have. +5 v, -5 v, ground, ground + 12v , sg,ac 115, 115
what is -5v, sg, and the second 115 for or is there a link to tell me what each one does
 
You have a Jamma cab. The power connections will be based off of your Jamma harness - look in the game manual. If I remember correctly the -5vdc interfaces with the sound circuit, the sg is just a ground (usually referred to as a field ground) and the second 115vac is not usually used but I guess it could go to a second monitor or the marquee light.
 
OUCH.

ADJUST THAT POWER SUPPLY!

First off... that power supply is way out of whack if you are getting 5.8v on the output. The safe operating voltage for TTL/LS/CMOS/HMOS, and other 5v logic is 4.75 to 5.25 volts.

5.8 is way up there in the fry chips territory.

It could also be why the power supply is shutting down.

If it's a cheap switcher then look in the openings of the case for the tops of the capacitors. If they have split open then replace the caps or replace the supply.

If it adjusts down to 5.1 volts and still shuts down then replace it.

RJ
 
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