Space Duel troubleshooting help

Pimpbot5000

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I've been trying to bring this Space Duel board back to life. Initially the self test indicated all the RAM chips were bad, so I replaced those. At that point the self test would pass but would immediately reset without displaying anything on the screen. I replaced the AVG chip with the Biltronix replacement and now the self test passes and displays without resetting. The game will not play in game mode however. The start buttons are lit (not blinking) and the screen is blank (spot killer is on).

One thing I noticed is that self test screen 3 does not display the rectangles it's supposed to. The manual indicates this could be a problem with the scaling circuitry. Looks like I need to check chips C7 and D7...? Any other suggestions are appreciated. Thanks,

Carlos

Self test screen 1
CIMG5160.JPG


Self test screen 2
CIMG5161.JPG


Self test screen 3
CIMG5162.JPG


Self test screen 4
CIMG5163.JPG


Self test screen 5
CIMG5164.JPG
 
I probed the 191 at C7 and several pins were stuck, so I replaced that and now the scaling is correct. Self test screen 3 shows the rectangles correctly. The scale is now correct on the other self test screens (I hadn't realized it was wrong.)

CIMG5171.JPG


CIMG5172.JPG


Unfortunately the game still doesn't play. To narrow down the problem I'll probably try Omegaman's suggestion next:

If you remove chip L5 (7442) and fit a socket. Place the chip back in the socket with pin 1 bent outwards (so that it doesn't go into the socket) if you can then power up the game and play blind you know you have a problem in the Vector generator.

Any other suggestions for narrowing this down are appreciated.
 
Duh... now that the scale is correct, I noticed that I can see more information on test screen 1! It's telling me that ROMs R1 and N/P1 are bad. So I guess the next thing I'm going to do is have some ROMs burned!

CIMG5174.JPG
 
Steph at Hobbyroms burned the two ROMs I needed and they arrived today. And... Space Duel is fixed! This is the first time I've repaired an Atari game, and I was really impressed with the depth of the self test as well as the documentation. Those Atari guys knew what they were doing.

CIMG5231.JPG


CIMG5232.JPG
 
Congrats!

SD was the first game I owned. Recently reacquired one and am very happy to have it back in the stable. A few more parts, and it will be complete. Then I get to start working on adding Gravitar, Black Widow, MH, and Tempest to the machine. :)
 
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