Trying to repair my Sega Space Ship vector cabinet...

f4brice

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Trying to repair my Sega Space Ship vector cabinet...

Hi all.

My name is Fabrice, 36 years old. I'm living in France, close to Switzerland.

I own a Sega Space Ship upright cabinet, which can be found on this Sega flyer :
http://www.arcadeflyers.com/?page=thumbs&db=videodb&id=3025
It's a 1978 vector game. Game PCB is TTL + analog (sound) based. It has no CPU.

My game is not working and I'm trying to repair both game PCB & screen.

I found that 1 (there may me more) problem with game PCB is chip IC138.
It's a MMI 32 x 8 bits ROM. One of this ROM data bit output drives the 3 latches chips (74LS377) which are connected to the X-Y screen.
This ROM seems not to be able to read anymore its content for some bits : D2, D3, D4, D5. Other bits look ggod.
When checked with oscilloscope, I can see bad & noisy output.

I could replace this ROM by an EPROM (it'll need only basic wiring) programmed by myself, but how could I have the old ROM content while it has bad output ?
I could not find any technical information on this game.

Regards,

Fab
 

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