Joust sound board / general CPU troubleshooting

87 t-66

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I'm trying to figure out an issue with a Joust sound board and am hoping someone can give me a hand... The R/W pin on the CPU, PIA, and ram are all stuck high and I'm not sure why. They are all connected together and should be toggling when compared to a working board. What needs to happen in order for the R/W to activate/toggle?20250820_192148.jpg
 
probably a working CPU? if you have another 6808/6802 try that. otherwise if the PIA is a AMI part it could just be bad and weighing everything else down. it's probably something I've encountered before but shotgun fixes seem to have worked in the past. lol
 
The PIA is NOS from APAR and the CPU works in my other sound board. The original PIA was doing the same thing.
 
When the CPU powers up, it tries to read instructions from the reset vector (FFFE-FFFF). If unable to retrieve, it may end up holding the R/W in a fixed state (intentionally 'Stuck'). I would start with the basics: Correct Power, Correct Clock at CPU (P38/P39), Reset not stuck, check address and data lines are not shorted (to ground, or each other), etc.

Also, putting a 6802 and removing jumper on Pin 36 (RE - RAM Enable) will force the CPU to use the internal RAM in lieu of the external 6810. Sometimes it's necessary to remove it from the board (or cut any shorted pins) to get the address/data bus alive.

~Brad
 
When the CPU powers up, it tries to read instructions from the reset vector (FFFE-FFFF). If unable to retrieve, it may end up holding the R/W in a fixed state (intentionally 'Stuck'). I would start with the basics: Correct Power, Correct Clock at CPU (P38/P39), Reset not stuck, check address and data lines are not shorted (to ground, or each other), etc.

Also, putting a 6802 and removing jumper on Pin 36 (RE - RAM Enable) will force the CPU to use the internal RAM in lieu of the external 6810. Sometimes it's necessary to remove it from the board (or cut any shorted pins) to get the address/data bus alive.

~Brad
would bad rom or incorrect jumpering do the same thing?

I've never probed the R/W pins before, I have no idea what that behavior is like :eek:
 
When the CPU powers up, it tries to read instructions from the reset vector (FFFE-FFFF). If unable to retrieve, it may end up holding the R/W in a fixed state (intentionally 'Stuck'). I would start with the basics: Correct Power, Correct Clock at CPU (P38/P39), Reset not stuck, check address and data lines are not shorted (to ground, or each other), etc.

Also, putting a 6802 and removing jumper on Pin 36 (RE - RAM Enable) will force the CPU to use the internal RAM in lieu of the external 6810. Sometimes it's necessary to remove it from the board (or cut any shorted pins) to get the address/data bus alive.

~Brad
I have verified power and the clock, reset is high. I don't have any 6802's on hand but just ordered a couple. I guess if I'm going to pull the ram I might as well leave it off and use the 6802. I'll report back once I've tried that and also look more at the address and data lines. Thanks 👍
 
I have verified power and the clock, reset is high. I don't have any 6802's on hand but just ordered a couple. I guess if I'm going to pull the ram I might as well leave it off and use the 6802. I'll report back once I've tried that and also look more at the address and data lines. Thanks 👍
you are running a Joust Video sound rom 4 2532 and the sound board is jumpered for it?
 
Fingers crossed...I piggybacked an unknown condition ram I pulled from a parts board and it didn't make a difference but hopefully the 6802 fixes it.
I wish I could be more help. I would need it in front of me which would require you visit, cause I don't want to do these through the mail anymore. lol
 
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