Arcade Collecting > Restorations & repair

saving a galaxy pinball

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ZZT:
Recently I buyed an old Stern Galaxy pinball in a very poor condition. Now I'll try to repair what is bad.


There is, cover with bird crap, dust, grapes (it was in a backyard from undeterminate time). I plug it in and no signs of live, except general ilumination.  :(

Next I try to open it and see what happend.

b.

pinballwizard79:
ive played this one, cool game

Paladin:
If you're lucky, the glass will have stopped any of that junk from getting to the playfield!  I'd love to see more pictures as you work on it.

ZZT:

--- Quote from: Paladin on June 02, 2009, 11:07:09 am ---If you're lucky, the glass will have stopped any of that junk from getting to the playfield!  I'd love to see more pictures as you work on it.

--- End quote ---
Yes you right, I'm lucky!! Playfield is in pretty good condition (only a little heavy dust layer).
I opened the backbox to see the propper operation problem and looking at the MPU the diag led is stuck on, bad news. I check all the power supply volts and its ok. Now I have to see the MPU itself.  :-\


I don't see any battery acid damage, so I think one or several chips are bad.

ZZT:
Good news!
Today I fix the MPU! Finally I found several bad chips.
 
U5 and U6 proms. Both replaced with 2716 eprom
U7 RAM. Replaced with 6810
U9 CPU. Replaced with  6800
U17 burned out, replaced with a new 74LS00
U8 & U13 CmosRAM. Both replaced with L5101.

After several hours I finally recover the propper operation of the MPU.
At the beginning the led is stuck-on, then, using a oscilloscope I look at  the clock signal and determinate U15 & U16 are good, at least clock signal is good.
 
In the next step, I tested the CPU 6800 in another know-good Bally MPU and mark as bad. In the same way I test the PIA chips (both goods) and the RAM 6810, bad.

The next step are test the prom's. I read the four chips in an eprom burner and determinate U5 & U6 are bad. The propper code was burned in a old (but good) 2716 chips.

Whit this new chips replaced the diag led start to blink, but just give  only two blinks and still "on". Then I discovered that U17 (74LS00) are burned out, I replace it but whitout changes (just two blinks). Then I replace both CMOS U8 & U13 and BINGO, after all replacements the MPU led gives the 7 expected flashes.


Here is a fixed MPU.  :dizzy:
I never seen another MPU so bad like this, I feel very very lucky.  :angel:

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