Sega16B Golden Axe - Memory Test Fail

rerror91

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Donor 2016, 2020
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Hello all,

I recently purchased my first arcade cabinet. The unit was built in 1982 by Atari for Namco's Dig Dug, distributed in Canada by Dale Distributing Ltd. The original serial number for Dig Dug is 3243. Sometime in 1989 or '90 it was converted to Sega's Golden Axe.

It appears to have gone through numerous owners. The wiring is a nightmare, but after a bit of patience I was able to get it functioning (video, sound, controls all work). The Sega/JAMMA breakout adapter has been hacked to hell, the speaker is getting raw fully-amplified audio so it distorts quite badly. I can fix all this, I just want to make sure the game board is good.

I was able to get the game into the "test" mode and ran through all the self checks. All control inputs are working, all sounds are working, ect. The only issue I ran into was when it came to the memory test:

MEMORY TEST MENU
ROM TEST
-A7 Good
-A8 Good
-A5 Good
-A6 Good
FIX VIDEO RAM
-H15 Good
-H16 Good
SCROLL VIDEO RAM
-H13 Good
-J13 Good
COLOR RAM
-J9 Good
-J10 Bad
SCRATCH RAM
-E9 Good
-E10 Good

Now the monitor in this cabinet is the original one from Dig Dug. It has been rotated 90 degrees and is quite dim. It also suffers from some pretty nasty burn-in. "© 1982 ATARI INC" is permanently visible on the screen :D. Because of this, I am not sure what effect (if any) the bad Color Ram has.

I wasn't able to find much information about the self test in the original installation manual from Sega.

Any help is appreciated!
 
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On those boards if it reports just one of a pair as bad it is probably just the RAM chip itself. You will need to take the ROM board off to find the RAMs.
 
The palette RAMs are two 6116 (most of time TMM2115 are used which are higly unreliable), they are on motherboard, you have to remove the ROM board to see them, they are @J9 and J10.It could be the chip itself or the 74HC273 which latches data bits from the SRAM (more likely the first case).

Refer to my repair log :

http://www.jammarcade.net/altered-beast-repair-log/
 
Thanks for the tip and link, caius!

I have removed the ROM board to expose the entire motherboard, seen here. I then identified the two UM6116K-2 chips and their D74HC273C "counterparts", close-up here (I put an arrow pointing to J10).

Visually, all the chips look OK. No burn marks, no bad solder joints, no shorts underneath from bent pins, ect.

I have an old Tektronix 453 AC/DC 50mhz oscilloscope I recently got fully operational. I haven't looked up the data sheets for the 6116 or 74HC273 but I will hopefully have time this week to do so and I can start probing the chips. I'm a little new to using the scope with digital electronics (I have only used it with tube audio equipment as a signal tracer and as a basic spectrum analyzer... way, WAY below what the scope is capable of). Any specific ohm-rating I should be using or other things I should be aware of? I know the scope is dated, uses a CRT and doesn't have a digital read-out, but I love the old half solid-state/half analog electronics... and it's all I have :D

Thanks again for the help, everyone. I really appreciate this community and their dedication to preserving the old coin-op machines. Been a lurker for years, had to create an account to coincide with my arcade purchase ;)
 
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What you see in the pictures is all I have, unfortunately. I will have to purchase some replacements or something equivalent. Know any good sources for these types of chips?
 
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