Galaga video board problem

mcandrewsoun

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Hi, Im getting a RAM 2L error on bootup. So far, Ive reseated the ROMs, changed the 50 pin cable, switched out several of the custom chips, and put in a new 2114 @ 3E. The cpu board tested fine on another video board. Has anybody seen any other causes of this?

Thanks,
Andrew
 
Yep..already popped a new ram in.

yes, I am still getting the RAM 2L error. The first thing I did was replace the 2114 @ 3E. I swapped all the roms and the custom chips. I was hoping someone had seen this caused by something other then RAM 3E, before I start shotgunning Rams.

Andrew
 
Have you ohm'd out the traces, and connections to the ram chip? You may have an open trace, or shorted trace.
 
Everything seems to ohm out ok. Theres lots of activity on it looking at the scope. There is a 74LS377 near it that seems to have some inactve pins..so Im gonna try tracing from there.
 
Does anyone know how the error gets generated?

It looks like all the chips in the data flow around 3E have activity.. Does anyone know what triggers the error code, what part of the circuit actually triggers it?
 
Bad RAM, bad socket, Dirty custom chip pins, bad custom chip sockets, broken resistor packs, bad ribbon cable, etc... follow the traces on the schematic backwards from the chip to see what you need to check.
 
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