Galaga not booting up, just garbage displayed

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I have a Midway Galaga machine that recently started not working. When it boots, there's a ton of garbage on the screen and no obvious self test display. Then it locks up hard with a solid tone.

I've made a video:
http://www.youtube.com/watch?v=Rl_TuBIZ_pY

At :07 you can see the "RAM OK" screen flash really fast. I don't see any ROM diagnosis though.

I initially suspected bad EPROMs. I checked them all, and one was indeed bad (dumped differently each time I read it). I replaced it, and also added the free play attract hack (http://forums.arcade-museum.com/showthread.php?t=229972). But still I get garbage. Any ideas?

Also, this cabinet seems to be a repro. The cabinet itself is very nice and clean, probably less than 5 years old. There's Galaga side art and CPO, and the monitor bezel. But the internals have a switching PC power supply and wiring harness that's missing the self-test switch. Did someone make new Galaga cabinets? The boards look original (I've attached a pic). And is there another way to put it in self-test?
 

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On a Galaga pcb, there's a whole ton of custom chips, with really frail legs that turn black... you have to carefully remove each one, clean the legs, and replace it back in the socket. You gotta go really, really carefully though because the legs will fall the fuck off the chip if you look at them wrong, then you have to Email Riptor and beg him to sell you some custom chips to replace the ones you just broke, lol.

That's where I'd start, if it was me.
 
On a Galaga pcb, there's a whole ton of custom chips, with really frail legs that turn black... you have to carefully remove each one, clean the legs, and replace it back in the socket. You gotta go really, really carefully though because the legs will fall the fuck off the chip if you look at them wrong, then you have to Email Riptor and beg him to sell you some custom chips to replace the ones you just broke, lol.

That's where I'd start, if it was me.

+1

You can see what he is talking about on that chip in the upper left hand corner. Aside from the crappy sockets and resistor packs (ChannelManiac now has more of the Galaga renew kits; hint, hint), The 07xx chip and the z80 chips are the ones to check first with a logic probe. It is kind of neat to watch the z80's spring to life all of a sudden (2nd and 3rd z80)
 
I'd start by cleaning the 08xx chips on the CPU board and replacing their sockets.
 
Thanks, I took out the custom chips on the main board and cleaned them. It works great now! The machine still boots up to garbage for about 2 seconds, but I suppose that's normal. It then goes into the initial self-test mode.

Is there a jumper on the board to manually enter self-test mode? The harness my machine has doesn't include the self-test switch.
 
Yeah it's normal for their to be garbage for a few seconds. It's like a mainly white screen with some boxes blinking on it.

Yep, that's a good description.

The machine was turned on at 8AM today, and around 11AM I noticed it was stuck on the "RAM OK" screen. I power cycled it, and it booted up back to garbage, and a crash. I cycled once more, and it booted OK. So I'm assuming there's a dying chip in there, or at least one that's still dirty. Is there any way to test the chips individually? I'd like to figure out which one is bad and then replace it.
 
You CANNOT diagnose chip problems without first replacing all the 24/28/40/42 pin sockets on that boardset.

If it has the old, flat style resistor packs then those must be replaced too.

Those are all common causes of glitches, errors, and crashes and you cannot find a bad chip if something else is causing problems too.
 
You CANNOT diagnose chip problems without first replacing all the 24/28/40/42 pin sockets on that boardset.

If it has the old, flat style resistor packs then those must be replaced too.

Those are all common causes of glitches, errors, and crashes and you cannot find a bad chip if something else is causing problems too.

I meant by pulling the chips and testing them elsewhere. Is it documented what they actually do?

The board has the newer style resistors.
 
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