Star Wars Matrix Errors

jkoolpe

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Hey folks!

Well, no sooner did I acquire an extra, working Star Wars board then my original board went down :( . Literally, the same day I picked up the extra SW board! Grrr!!!

So now, when I play the game, it sometimes works for a short while, and then all of a sudden, the starfield disappears as do the enemies. I can still see my X-wing, I can still fire my lasers, and the sounds and music are all there, but no stars and no bad guys. And the game does not progress beyond the first wave either. Here is a short video:

http://www.youtube.com/watch?v=vdSp2eN2N8g

In the self test, I get the dreaded "matrix errors" and everything else passes OK. The error messages are sporadic in that sometimes they read OK, but then as the test is rerun, the errors show up again, flashing on and off. Here is a picture of the error message when it is steady:

http://i140.photobucket.com/albums/r4/jkoolpe/Star Wars problem/StarWarsMatrixError.jpg

I have tried swapping the matrix RAM chips and also the PROM chips with the working board, but no change. I also swapped the AVG chip with no luck. I have the schematics and a scope and can start looking at the matrix chips as shown in the manual on the main board. Any best ideas of where to start on this board?

BTW, this board has Clay's ESB kit installed if that matters.

Thanks,

Jon
 
Well... it seems lucky that you have a problem that occurs only part of the time, so it may be easier to troubleshoot if you can isolate when it happens. I believe you can run a boardset without the sound board, which will give you full access to the main board (you might want to verify this with someone else).

Then I'd first start by feeling the chips for hot ones, and maybe pressing on chips a little to find bad connections/broken traces. Then I'd go to the hair dryer and see if heat can make the problem consistent (and narrow down the area). Then I'd go for the freeze spray to hopefully "fix" the problem. Then just replace that IC. In the few boards I've repaired, I've come across a lot of bad 74LS245s, so I'd especially check them.

Do you get the BAD MATH READY LINE? The way things disappear, it looks like that line is getting intermittently stuck low... so I'd check the signals connected to that on the schematics.

DogP
 
. I believe you can run a boardset without the sound board, which will give you full access to the main board (you might want to verify this with someone else).

You can definitely do this. The game will pass all the tests and play perfectly without the sound board. You just won't have any sound. :D

-Ian
 
You can definitely do this. The game will pass all the tests and play perfectly without the sound board. You just won't have any sound. :D

-Ian

Thanks for the confirmation... I remember disconnecting mine while testing my boards in test mode, but I never put it into game mode without it hooked up.

DogP
 
Good info...thanks guys.

I was wondering if the board would be OK if I took off the sound board and fired it up as I would need to do this to work on it.

I saw in the schematics that there are 2 LS245 chips in the matrix section that are listed as "matrix processor data selector" which seems to be part of the initial matrix section. A logical place to start.

I hope to have time to sit down with my scope later this week...one problem is that I have to test the board plugged in to the wiring harness from the back of the game as I don't have a test bench (so I can't see the screen as I might be pressing down on potentially bad chips...I'd have to borrow a second set of eyes...I'll have to enlist the wife again :) ....she's a trooper!

Jon
 
Let's re-order that paragraph ;)

one problem is that I have to test the board plugged in to the wiring harness from the back of the game as I don't have a test bench (so I can't see the screen as I might be pressing down on potentially bad chips...

I hope to have time to sit down with my scope later this week...

There's your solution... who needs a monitor when you've got a scope? :D

DogP
 
Heh, well... Star Wars is a difficult cabinet to use with a mirror, especially since the wiring harness isn't very long, so you're pretty much stuck at the back and bottom of the cabinet. Some sort of monitor on the floor right at the back of the cab is nice ;) .

DogP
 
Heh, well... Star Wars is a difficult cabinet to use with a mirror, especially since the wiring harness isn't very long, so you're pretty much stuck at the back and bottom of the cabinet. Some sort of monitor on the floor right at the back of the cab is nice ;) .

DogP

Well...I do have an XY monitor extension cable and a Space Duel sitting right next to my SW...I suppose that could work :) .

Jon
 
Well, I finally had some time (after CAX was over :) ) to look at my malfunctioning SW board. I sat down with my o-scope to do some probing on the chips in the designated matrix area (from the schematics). Sure enough, I found some dead signals in some of the chips and was in the process of trying to track out the true culprit when all of a sudden the board fixed itself.

The dead legs on the chips I had been probing came back to life, and the starfield/enemies were back on screen. I left the machine on for a couple of hours, played some good (long) games, and then retried it the next morning, and it's still working just fine now.

I do not know what I did...but I was suspecting either the matrix 74LS245 chips, or possibly a matrix address selector chip at 8H I think it was...but then everything was good so I didn't go further.

Maybe a bad socket for one of the PROMs? I know the PROMs themselves are good as I swapped them with known good ones from my extra working boardset...

I guess if and when it happens again, I'll start the process again, but maybe I'll be lucky this time :D ...

Jon
 
Maybe a bad socket for one of the PROMs? I know the PROMs themselves are good as I swapped them with known good ones from my extra working boardset...

Thought you were going to swap the prom sockets? Sounds like you got lazy and played a few games instead. ;-)
 
Thought you were going to swap the prom sockets? Sounds like you got lazy and played a few games instead. ;-)

Yep...but not lazy...just need more time :) .

And I'll have to get to it again, as sure enough, the problem re-occurred last night. Not surprised really...I still think it's probably one of those LS245 chips or maybe a "matrix address selector" chip. Hope to have some time this weekend maybe...

Jon
 
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