Repair Log: Joust Boardset

YellowDog

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Donor 2011, 2013
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I recently got a Joust (1 MPU, 1 I/O board, 2 ROM boards (a solid green and a striped green ROM set) and 1 sound board) boardset to work on that was mostly dead. A quick power up confirmed that the ROM ribbon cable needed to be recrimped. After doing that, it showed signs of life. But not consistantly. A second recrinping of the MPU side connector and it started Rug Test. And promptly died.

Logic probe showed that it was being killed by the watchdog circuit. So it passed the POST as evidenced by the 0 on the LED, but the game didn't start.

I pulled out the magnifying glass and started to look for cracks or tears in the traces. Nothing. So for grins, I started looking at the traces on the top of the board. Nothing there, but I did find one of the transistors smashed down so that two legs were touching. A second transistor was also smashed down, but one of its legs was broken off. So a little careful bending with a dental pick and the first transistor was standing tall. THe same treatment for the other and a quick solder on the leg to reattach it and it was time to try it again.

Power on. Rug Test. 0 on the LED. The screen cleared and the Joust logo appeared. Yea! I let it run for a few minutes and then powered off and plugged in the second ROM board.

Dead. Again. Rats!

I recrimped the ribbon connectors on the second Joust ROM board and was rewarded with a partial Rug Test. A second recrimping and got the full Rug Test. Followed by the Logo. Followed by the demo screen, which was messed up. Followed almost immediately bu the Rug Test. Rats! Again!

Since the MPU board seemed to be working, I focussed on the second ROM board. The first thing I noticed was that somebody had hacked one of the isolation capacitors near the first Special Chip by soldering it onthe the leads of the original capacitor. Usually that is a sign that somebody tried prying the chip out and used the glass capacitor for leverage. Not a good idea. They shatter quite easily. So I desoldered the capacitor, cleaned the holes and inserted the replacement cap. Plugged every thing back together and tested. It was a little better, but still not quite right. THe only thing left that I coul think of was to pull the Special Chips and reseat them, which was obviously what was going on when the original capacitor got broken. Once I pried the first Special Chip out, I could see the problem, one of the legs was bent under. I carefully bent it straight and reseated it. Power up, wait for the demo screen. It was perfect.

The I/O board tested out just fine.

Next up will be to test the sound board, but enough for one night.

The proof is in the pictures. Sorry they are a little fuzzy, the batteries in my camera were dying.

The Logo from the first ROM card:
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The Logo from the second ROM card
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The boards showing the bautiful 0 on the LEDS.

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So with a couple of hours worth of debugging and a little soldering, another Joust boardset lives again!

ken
 

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Nice Ken, very nice.

I have a couple of choice boards for you to play with, when I get a chance to dig them out.

Thanks Dave. I have boxes of boards with weird quirks. Every once in a while I think about just buying a set of chips, ripping everything off and starting from scratch on some of these. The only thing stopping me is that I have no idea how much it would cost to get a collection of all those obsolete parts :eek:.

Nice work. And thanks for posting the fixes. It's always nice to see what the problem was.

Thanks. We always see the problems, but hardly anybody posts how they fixed it. I will be starting to do more of this, time permitting.

ken
 
Did you just happen to take both screen pics at the exact same moment in the attract mode, or are they missing the left side of the border?
 
Did you just happen to take both screen pics at the exact same moment in the attract mode, or are they missing the left side of the border?

I was waiting for somebody to ask. This is one of the 7" LCD monitors I was selling off last year. There is something strange with the sync on Williams boards. The picture is stable, it is just off centered. The centering adjustment doesn't move it so I am not sure WTF is going on. I just use this one for my bench testing so it's no biggie. But I plan on making a portable JAMMA tester and I would really like to have it figured out by the time I have that put together.

ken
 
Awesome Work Ken! Thanks for posting the details, it helps me understand what to look for on boards with similar problems!
 
Gotta love it when chip pullers bend legs over, makes for an easy repair.
Now get those alkalines off the cpu board before they puke all over it :)
 
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