Galaga reboot problems

BobsterD

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I have a Galaga that for some reason decided to go into a constant reboot from the start up test program. It runs through all of the tests, gets to the grid, then starts the tests all over again.

I have 5.2v across cap C1 so that looks good. I have a switching PS in this unit and the 12V is actually at 13.4v...is this too high?

Any other ideas?
 
I have a Galaga that for some reason decided to go into a constant reboot from the start up test program. It runs through all of the tests, gets to the grid, then starts the tests all over again.

I have 5.2v across cap C1 so that looks good. I have a switching PS in this unit and the 12V is actually at 13.4v...is this too high?

Any other ideas?

Start re-seating the chips on the CPU board. That's a good place to start. It then moves on to checking for corroded off pins and bad sockets.

- James
 
Check the voltage directly at the processor to see what +5 reading you get. Sometimes it drops as it comes through the board. You want about +5.2 there....
 
My Pac did this when I swapped ROMs. One of the ROMs didnt get seated all the way and it came back bad. Reseating should fix your problem. If not, switch it into test mode to see if a ROM/RAM error comes up. If thats the case, you have a bad ROM
 
Thanks all... re-seated the roms and no luck. I'm not a tech so I'm looking for the basics before shipping this for service.

One interesting thing... on the CPU board the chips in 4M, 4J, and 4E get warm to the touch, yet the chip in 4H is cold. This chip is also designated only with a "5103" on it whereas the others are all NEC D780C-1. Is this a clue?
 
Thanks all... re-seated the roms and no luck. I'm not a tech so I'm looking for the basics before shipping this for service.

One interesting thing... on the CPU board the chips in 4M, 4J, and 4E get warm to the touch, yet the chip in 4H is cold. This chip is also designated only with a "5103" on it whereas the others are all NEC D780C-1. Is this a clue?

Probably not. It is good that you observed this though. You are well on your way to becoming a "tech". :)

The NEC chips are Z80 CPUs and the 5103 is probably a Namco custom chip.

If you have a good multi-meter or O-scope, I would check for ripple on your +5V. Then I would pull the ROMs and verify that they have not suffered any bit-rot.
 
I have 5.2v across cap C1 so that looks good. I have a switching PS in this unit and the 12V is actually at 13.4v...is this too high?

Probably a problem w/ the 2nd or 3rd cpu / rom / bus interface chips, or their crappy sockets. If you've got the brown sockets, they definitely need to be replaced.

12v at 13.4v is fine -- it only feeds the audio amp.
 
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