Bringing Joust back from the dead!

Parzval

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Donor 7 years: 2017, 2020-2025
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OK. I purchased a non-working Joust along with some other games a couple months ago. I finally had some time, so I decided to start with the Joust as it was the one supposedly working most recently though having some lock-up issues, which progressed to non-working altogether. Plus... I just love Joust. :)

Plugged it in: no 12v. Found missing fuses for the 12v. Replaced the fuses and 12v now present. Board getting all necessary voltages... but no activity from the 7 segment.

The boardset was rocking red ROMs but had 2 replacement ROMs... #10 with a green dot sticker, and #7 with a red dot sticker. Checking with the ROM files, #10 for a red set should be red, not green... and a checksum showed it was truly a green rom. Ok, on to #7... also should be red, it ALSO matched green rom. Programmed a proper red pair and installed. Still no activity.

Decided to make a ROM dump and check all the ROMs. Every ROM but 1,2, and 4 had bad checksum! Programmed new for the defective ones.... still no activity. Checked the ribbon cable for continuity... all good. Ribbon had been replaced, but gave a crimp anyway just in case. Still no activity. Reflowed all the connector pins while I had it on the bench.

WELL, back to the KLOV for more reading up. Consulted Lon's Joust Repair Log thread [located right here ---> https://forums.arcade-museum.com/showthread.php?t=398434&] Thanks Lon! It's already proving useful. :)

Lon's Log pointed me to a 2011 thread from YellowDog who had also had a dead Joust behaving like mine. (Probed my ROM board and found lots of inactivity.) He found the CPU installed backwards. Well, whaddya know... so was mine. And in addition, a broken leg! Swapped in another 68B09 and whoa! was that noise? (It actually startled me :laugh:) Monitor showing lots of activity.. but not right... but it seemed to light garbled blocks sequentially like the J-O-U-S-T coming up on screen.

Getting a really weird code. (Left my note at the house but it was if I remember right it was: [blank]-[backwards lowercase c]-7. Seemed like the left vertical segments were not responding... though they do all simultaneously blink at shutdown. Getting some fuzzy outputs on the BCD. Then the 7 segment stopped altogether. Probing also found a few other bad chips on the CPU as well. Had to order some parts, will be back at it when they come in!
 
So, got some time and hit it with the "shotgun" approach and just replaced the 7 or so chips that had some inactivity. The chips and sockets were cheap. No improvement, and the same chips still exhibited inactivity.... occasional outbursts from the 7-segment, and occasional sounds, but all the same as before... so, next!

While I had the boards on the workbench, I noticed what a horrible solder job was done on the replacement ribbon connectors. Cold joints abound. Excess solder everywhere. In fact there was even a solder bridge. Cleaned and re-soldered the connections, and was rewarded with an almost-rug pattern. Not right, but rug-like for sure. Re-flowed the pin connectors while I was at it too.

I decided to try a processor swap with my spare Defender CPU... and guess what... it's not a Defender CPU at all. It's a Joust! Huzzah! So swapped that board in, and since it was missing the video ROMs I had to swap them over. When changing the video chips over, I notice the #6 ROM in the top, and #4 is in the bottom. Who the heck worked my boardset? Nothing is where it belongs. Swapped them into the spare board so they're right, and received a pretty stable screen of wide vertical bars. Alternating dark/light, (3 of each I believe). Though here is some shrapnel that pulses along the bottom of the screen. Since the replacement board has a cut trace (which when bridged brings the sync back) I swapped back to the original board. With the ROMs in the proper spaces, I get the vertical bars with the old boardset now too.

Now I don't know what took me so long to check the processor reset line.... BUT I've discovered that it constantly pulses. Watchdog issues so I read. And that shrapnel on the screen... well, it pulses in time with the reset line. And when digits (or digit pieces) appear in the 7-segment they also pulse/disappear in sync with the pulsing reset line. Same with any sounds that happen.

SO... we're watchdogging here. Pushing reset knocks it low, but when it should go high, it pulses. Both CPU boards behave identically, so I'm going to wager it's the ROM board. I cleaned up the ribbon connections on that and noticed a few sloppy ROM socket solder jobs, so I cleaned a few and found at least 3 with no PCB pad! UGH. Anyone have a recommendation on how to fix that? (jumper wires I guess?)

Anyone have a spare ROM board? Can be populated, but mostly I'll need a good board with intact traces. My ROMs are good and I've got plenty more and a burner. Specials would be nice, as I have no spares.

So, on hold until I have time to mess with the traces, or until I find a board!
 
Good work, interesting thread. I've never worked on Joust so I have no specific feedback, but it sounds like you're making good progress and checking all the things I'd check.
 
Lon, I was just logging on to tell you I posted it a while ago...it's two posts above your post today in the log. :)
 
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Try to find a fellow KLOVer near you that has either a Joust, Robotron or Stargate board that is confirmed working. Simply swap out your ROM board with a known working ROM board and that will direct you to either further diagnose your ROM board or go back to further diagnose the MPU board.
You can unplug the Widget board while testing as well as the Sound board. I've had a shorted widget board one time that kept the game from starting up - it had symptoms like yours. I unplugged it and the game booted. All you need is the MPU and a known working ROM board to get the game to boot and go from there.
 
Try to find a fellow KLOVer near you that has either a Joust, Robotron or Stargate board that is confirmed working. Simply swap out your ROM board with a known working ROM board and that will direct you to either further diagnose your ROM board or go back to further diagnose the MPU board.
You can unplug the Widget board while testing as well as the Sound board. I've had a shorted widget board one time that kept the game from starting up - it had symptoms like yours. I unplugged it and the game booted. All you need is the MPU and a known working ROM board to get the game to boot and go from there.

My widget is a bit funked up with some dodgy repairs, but I've always done all the testing leaving it unplugged: CPU and ROM only. Disabled the watchdog too once I realized it was going off. AND I had purchased a ROM and Widget on eBay last week to do this very thing. Just waiting on it to arrive. Of course going off a eBay listing as "working" is far less reliable than a fellow KLOVer. We'll see. But then again, sometimes I get untested stuff cheap that actually works! :cool:

.
 
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Now we're getting somewhere!

Picked up a ROM board off eBay and it arrived yesterday. Totally unmolested original... with the exception of some wonderful mouse pee smell. Ewww. Plugged it in as-is for a go and gots nada. Gave the ribbon a pinch... and ho, got some activity! Flaky flickery garbage on the 7-segment. As-good if not better than what I've been getting with my bodgered up ROM board. So, put a new ribbon on the board and bingo! 1-3-1 on the LED. First actual real thing I've ever seen on there. (And the mouse smell disappeared too. Bonus!) Swapped good ol' 3rd bank numero uno with numero dos... aaaand still 1-3-1. Sigh. Well can't expect it ALL to work out instantly.

The last time I worked on the boards I'd left the spare CPU in the cab.... so, swapped it back out for the one that came with the cab. And... nada. Seems that CPU is not working. I swear someone along the line just dumped every garbage board they had into this cab to sell it as "complete". Set it aside to work on later and put the replacement CPU back in the set. Well, at least I'm getting somewhere. I was beginning to get frustrated. All the sockets on the spare "working-ish" board are the good ol single-wipe jobs, so I'll spend the next repair session time swapping them out for some solid new double-wipe. And also spend a little time on the forums to refresh my memory on what else to look for now that I have some codes.

I'll drink to today's progress. Feels good to see those digits light up.
Cheers! :cheers:
 
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