Joust crashed - need a start point

WiiKnee

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A few months ago my Joust took a dump :( In the middle of a game, it just went out with a garbled screen. I haven't had time to look at it, and am looking for a place to start trouble shooting. The PS has been rebuilt and works good (all three lights on). I have a known working sound board from Yellowdog. When I power up, I just get a carpet with some active garble. The fuses all check out. The ROM board LED display does not initialize and returns no error codes (doesn't even come on). So, looking for some advice!

Thanks,
Chuck
 
Check the voltage to your ROM board. Try flexing the ribbon cable between the ROM board and CPU to see if it comes up.

I recently had a Defender (similar hardware) that would continuously reset during the rug test, and tracked it down to a bad ROM. Once that was fixed, it booted and played fine...
 
Check the voltage to the memory chips. Could be low due to bad connections. Try reseating the connectors. Any plugs to the power supply burnt? If so, replace. I had a burnt connector on one and the inside was melted enough that the connector came out. Could be a bad ribbon cable or other connector issues. Bad RAM is still a possibility as the previous poster mentioned. My Joust started acting up and found a bad ground connection to the main board.
 
thanks for the tips! I previously rebuilt all the connectors on the power circuit and everything is good, nothing burnt. I am getting 4.86 volts coming into the ROM board. Flexing the ROM/CPU cable didn't help. I noticed that, at some point during testing, for a brief nanosecond, the ROM LED display briefly lit - not long enough to show any digits, but a sound was initiated and played out until it was completed.
 
I've only debugged the rug test in detail on a Defender, but the sequence should be similar - two passes of rug test, screen clear, self-test results displayed. How far does your board get? Do you make it to the screen clear, reset during the first/second rug pass, .. ?

Most likely something is sending the CPU off into the weeds (which will cause a reset from the watchdog circuit) - e.g. bad code fetched from ROMs. There are only a portion of the ROMs needed to get to the self-test results screen - according to arcadesolution.com, on Joust these are 12, 6, 7, 10, 11. I would remove the unnecessary ROMs first and make your first milestone getting to that screen.

Here's the link btw:
http://www.arcadesolution.com/rom.html

LeChuck
 
Thanks for all the help and guidance everyone. I decided to fold up my hand on this board set - it has given me nothing but trouble since day one and I am pretty sick of throwing time and money at it. So, I 19 in one'd it to death :) Really, I think it is the best thing I did. I am not a purist when it comes to games that use standard controls and I did minimal cab modifications. It was a pretty fun project converting it over to JAMMA and now I have confidence when it is on. I am pretty impressed with the 19-in-1 emulation, quite accurate. I have a dedicated Defender cab, so I don't bother with the emulated version. My three year old just loves Super Mario Bros :)
 
Let me know if you decide to get rid of the Joust set. I buy non-working board sets (which pretty much describes everything on eBay ;)).

ken
 
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