Galaga issues - newbie here

Sig938

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I brought home a non-working Galaga. Replaced the power cord and it powered up. There was sound and picture but the fighter was upside down as was the high score display and this was at the bottom of the screen (credits were at the top, upside down). Controls didn't work either. The enemy bees were ok though. So I turned it off to "reset" it. Turned it back on and get no sound and only white screen.

Bought a switching PS with the adaptor from Arcade Shop. I'll be rebuilding the original PS someday, just wanted to get it running for now. I pulled all socketed chips and cleaned their legs. Reseated and double checked my work. It powers up and looks really good and can play but has no sound other than the explosions when fighter is killed.

I bought and replaced the proms at 1D and 5C (from Bob Roberts) after researching this issue but it didn't change anything. One thing I've noticed is that with the switching PS I get the +5v but the +12 reads at 14.2v both at the switcher and the 3 pin molex connector on the PCB. I can't get close to +12v. I can lower the +5 to 4.8v but that only brings the +12 down to 13.XXv (can't remember exact numbers and I'm at work now). Is this a problem? Having the +12 that high? Did I get a faulty switcher?

What else could be causing the no sound issue? Would a CAP kit for the PCB help?

Any ideas/suggestions/comments will be greatly appreciated!
 
Clean the edge of the PCB and then plug it back in and test +5V at the edge of the PCB. I've seen high voltage cause things like this as well as low voltage. Don't worry too much about your +12V.
 
First, I'm surprised all the socketed chips stayed intact when you pulled and reinstalled them. You are lucky as most of them loose legs.. Do a search on Galaga sounds, the explosion only sound issue is well documented.
 
Thanks guys. I'll see what the edge of the PCB shows tonight.

Yeah, guess I was lucky regarding the legs. I've read about them being fragile so I was very careful. Took me about 5 hours to do both boards.
 
Well after more research I think the next step is to replace the CAPS on the PCB. I will report back when I get that done...hopefully sometime this week.

Another issue that came up yesterday was that the game locked up and the credits line showed "CREDITS FF". Never seen this "FF" before. Any ideas what that is? I was able to turn the game off, let it sit a few minutes, then turn it back on and it worked again (minus the sound still of course).
 
you've gone beyond numbers. your credits have gone plaid.

caps are good if you're losing substantial voltage between the power supply and chips. the PSU guide in my signature is intended for JAMMA games but its actually identical philosophy. the edge and filter caps are important.

additionally, I took all the chips out of a Galaga board and didn't lose any legs. should I play the lottery next?
 
Well CAP kit didn't do anything. It now gets stuck on the start screen with the credits showing "FF" right away. Not even able to play for a bit before this happens anymore.
Voltages are good. Guess it's time to find someone to send it to for repairs.
 
Well CAP kit didn't do anything. It now gets stuck on the start screen with the credits showing "FF" right away. Not even able to play for a bit before this happens anymore.
Voltages are good. Guess it's time to find someone to send it to for repairs.

You probably need to start replacing the IC sockets. The fault sounds like it could be the custom IC's for the coin/credit counting, the 51xx custom IC ( big 42 pin one ) , or the I/O interface custom IC 06xx, 28 pin. From past experience it's often the socket for the 06xx causing coin & I/O problems, providing you don't have any cracked IC legs.

- James
 
You probably need to start replacing the IC sockets. The fault sounds like it could be the custom IC's for the coin/credit counting, the 51xx custom IC ( big 42 pin one ) , or the I/O interface custom IC 06xx, 28 pin. From past experience it's often the socket for the 06xx causing coin & I/O problems, providing you don't have any cracked IC legs.

- James

Also replace any and all flat resistor packs. A renew kit has all the sockets and resistor packs. I personally like to get board working first, then install renew kit.

http://www.arcadecomponents.com/catalog/item/6799687/7841050.htm
 
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