Arcade Collecting > Restorations & repair

My First Restoration - Galaga!

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erlsjj:
Sunday, 30 Nov 2008:
A good friend of mine invited me to an arcade auction up in Grandview, MO. He went home with a very nice Spy Hunter (with garbled music - which he fixed by replacing the digital analog converter), and I somehow became the proud new owner of my very own Galaga! I paid $200 for it ($197.75 if you count the 9 quarters I found inside the machine).

erlsjj:
Dec 1 - Dec 12, 2008:
The monitor worked, but no game. I measured the voltage going into the CPU PCB and it was reading 0.398V. Just a tad low. Variable resistor did nothing. After troubleshooting the power supply board, I found a bad 2N3055 transistor on the heat sink. I replaced the bad transistor as well as 4 bad diodes (all 4 were my fault which gave off some impressive blue smoke!), and after finding poor solder contact at the variable resistor (thanks, Jason), the power supply board was producing sufficient voltage (adjusted to +5.18V).

erlsjj:
Friday, 12 Dec 2008:
With the power supply board now producing +5V (and +16V on the other pin - not sure why it's so high. Spec says it should be 13V?), I was hoping this would fix it, but all I see is a diagonal pattern of stars  and a high pitched single tone coming out of the speaker (I will post a video once I figure out how).


Sunday, 14 Dec 2008:
My friend helped me move my Galaga to my house. Boy, was the wife in for a surprise! ha ha! Turns out, she thought it was a pretty cool project to be working on (as did the kids).

erlsjj:
Monday, 15 Dec 2008:
Anyway, I took the CPU and video boards out to clean them. Pretty dusty. I pulled all the socketed chips off one by one and cleaned the legs with a small brass brush. I also checked the ribbon cable. Connectors and cable looked ok. I did notice the 1N chip on the video card was suspiciously missing with a jumper wire not attached to anything. Anyone know if I need this chip? According to the spec, 1N is supposed to be populated by a 07xx Custom IC. Did a little research and the 07xx chip is for the clock divider counter array (whatever that's for).

Tuesday, 16 Dec 2008:
Stuck for now. Started discussion thread to try and solicit any help/advice.

Wednesday, 17 Dec 2008:
I'm contemplating getting a new CPU board and/or video board, but I'd really like to isolate the problem first. Maybe it's that missing 1N chip...

RayB:
Regarding your video... you're not supposed to use the "html" embedding code. Just click the little Youtube button when you post here (its right under the "BOLD" button) and then paste in the URL of the video.

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