NARC - U58-U44 Rom Error

Harvs

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Just picked this machine up.. Needs a new Flyback, moving the 'screen' knob can turn the monitor off/on. That will be on the way along with a cap kit.

Plays fine except for random lines throughout and a bit of image flickering as seen in pic.

I reseated all Roms.. Do Roms go bad like that or should I try something else? I read about 'bank switching circuitry', but there was no response on that after it was mentioned.

Thanks for any advice!
 

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I've seen this happen before. and it's strangely enough in the CPU board. I bought all replacement chips for a rom board and changed them all and it didn't go away. a friend of mine donated a CPU board and that made it work again.

I have tried replacing those same chips with a CPU board throwing all bad video roms and haven't been able to crack it.

and nobody here seems to know what to do.

additionally, your rom errors will cause artifacts on the screen. the CPU board isn't able to decode the data coming off those red roms.
 
I've seen this happen before. and it's strangely enough in the CPU board. I bought all replacement chips for a rom board and changed them all and it didn't go away. a friend of mine donated a CPU board and that made it work again.

I have tried replacing those same chips with a CPU board throwing all bad video roms and haven't been able to crack it.

and nobody here seems to know what to do.

additionally, your rom errors will cause artifacts on the screen. the CPU board isn't able to decode the data coming off those red roms.

Are those CPU boards readily available? Costly?
 
I got a whole set from Quarter Arcade and that had a dinged up CPU board as well (3 of the 4 rows of roms came up green). so this is probably pretty common.
 
Follow the schematics... There are some 74LS138 chips on the ROM board that generate the ROM enable/select signals. Follow the 3 select lines (pins 1-3) and 3 enable lines (pins 4-6) on those backwards from those chips to find where the signals are failing.

If you can read a map you can read a schematic. It's easy once you get the hang of it. :)
 
Follow the schematics... There are some 74LS138 chips on the ROM board that generate the ROM enable/select signals. Follow the 3 select lines (pins 1-3) and 3 enable lines (pins 4-6) on those backwards from those chips to find where the signals are failing.

If you can read a map you can read a schematic. It's easy once you get the hang of it. :)

this sounds like a fun experiment for later.
 
Well, I think I've narrowed down the problem with NARC having rom issues.. I bought an 'untested' board and even though I prayed a lot, it didn't fix the problem.

By swapping around the L1A3787 CPU chip pictured, the problems followed that and not the CPU board itself. The 'untested boards' L1A3787 gives all rom errors, while my original only gives rom errors from U58-U44.

So, does anyone have an L1A3787 CPU chip for sale? And are these L1A3787's specific to NARC only??
 

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Not specific.

I have a couple here... $12 shipped priority mail if you want one.

Raymond
 
that's the Custom Chip. I think aren't the CPUs hardwired on these?

I popped the 'all rom error' chip in my original CPU and it showed all rom errors.. Took my original 'U58-U44 rom error' chip and put that into the other CPU and it showed only U58-U44 errors.

My conclusion - The rom errors followed that specific chip no matter which CPU it was installed in, no other chip swapping changed anything except for.

Excuse my dumbo terms for the chips/board names etc.
 
Worked like a charm.

So now I have 2 working NARC CPU boards and 2 shit L1A3787 chips. PM me if anyone needs a working NARC CPU.

Thanks Raymond!
 

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Worked like a charm.

So now I have 2 working NARC CPU boards and 2 shit L1A3787 chips. PM me if anyone needs a working NARC CPU.

Thanks Raymond!

Happy to help and glad two more boards are alive and kicking!
 
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