Arcade Collecting > Restorations & repair

Galaga upright restoration

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kayoteq:
I tried spotting varied chassis that would be useful, but a majority were post 1990s and besides I wouldn't know a wells-gardner from a garden well. ;0 but I did get a few chassis for fun and amusement, will put them on the site once I've photographed them.

Back to Galaga:

Right off the bat, I'm not getting voltage past the big block. The switching power supply has no juice.  Time to go through the pile of switching power supplies and pick out a new one and start utterly over with the power upgradde mod.


I don't seem to have the wire  connector between the CPU video and the monitor. G07, that is. Must have alll been scavenged in storage. I have alternative connectors, but anyone with a spare-- I have plenty of spare minor cabinet parts to swap. PM me ..

Stage 1: Wiring

kayoteq:
Power problem found, wt?


two reasons I'm considering starting over with the spare.
The inset picture is a wire that was put aside with care,
while it's corresponding connector wire is.. a bit bare.
I would not, should not, plug in the CPU, even on a dare!

Mauzy:
Looks like they cut out the interlock switch. You could put a female connection on each of end and pick up a  up for like 3 bucks on eBay or elsewhere. With that switch missing, if everything other than those two problems is normal, you can plug in your CPU all you want. No power will go to it. The interlock switch on the back is a safety which causes the machine to go off when you open the back door.


I am jealous of your mad rhymes.

kayoteq:
Electrical mayhem resolved

Part 1: AC
Safety interlock switch rebuilt (remember, the spares pile?)
fuse replaced coin door lights replaced..
bzzz... the low pitched hum of something.
Slight glow from the flourescent and then spectacular meltdown of the ballast. Okay, not spectacular, but nonetheless it went.
(spare ballast installed)
Puzzled overnight with that.. even my incandescant fixture wouldn't work..
morning came and duh- change the fuse that properly blew after the ballast went.
Probe reading verifies 120v where I had 25 before..
Also changed the starter thing just for fun.
Blink-blinkety.. now I can be enlightened by the B- grade Galaga marquee and know when the power's hot!


Part 2: DC
Tweaked all the conenctors, and traced down the disconnected wire- yellow/white and goes to the corner of the cpu harness.
schematic says logic ground. So.. That _should_ mean the ground on the switching power, correct?

Getting as much correct as possible before even letting the cpu near it.

Off to Step 2: Video

Rainy day, so I hooked up the Galaga once I found the video cord.
Self test, stuck at RAM OK. Chip at 4D (which they had labeled as bad) is hot!
At least it lives.. just confused.

kayoteq:
Sorry if I seem to be talking to myself, but hey, I read these forums all the time to see how someone else solved a problem..


Problem 1: I don't know how to designate CPU from video. it's the Video 4D that was funky.
it's an eprom, not a clock thing. Which had made the techs I bothered quite puzzled as to why I was getting a screen.

By incredible luck, I had an original eeprom on foam in the cabinet. put in its correct place and took the mod chip ("fast") is all it says
and put it in the Video 4D. The contents would be wrong, but safe.

No more blocky graphics, but still stuck at RAM OK.

When I was figuring out the chip problem, I noticed an discrepancy between my diagrams and my board. As in, one of the
z80 chips was upside down. Turned it around, same result RAM OK. Same result? as if, the z80 is dead??

Went to my junk pile and extracted an appropriate z80 CPU (not z80a) and put it in the flipped CPU's sockekt.

BOOM

The good kind. It lives. Strange, blocky shapes that attack me when I give it quarters. But I expected such results there.

Now on to the normal thing this topic is for, Restorations.  And a purchase of a new Video 4D  eeprom. And lots of restoration parts
that would otherwise been going towards someone else figuring out the two-chip problem.

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