Haunted Joust Input issues

dethfactor

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Howdy.
Been working on giving my Joust an overhaul. It's been sporadic and acting haunted for a while. (games starting by themselves, controls not working at all, ram errors, sprite glitches, red popping in and out) Some days it's a champ and sometimes it's all over the place. Needless to say, I've rebuilt the PSU, recapped the boards, replaced all the connectors, cleaned / reflowed the pins and replaced the ribbon cables. And I'm still having a few issues here or there. I'm in the process of doing a RAM upgrade but there's 1 input issue that's still happening. The player 2 flap is stuck closed. I even booted with the CP unplugged and it's still closed. I've traced it out and the switches are fine and the wiring looks good. So I was wondering if anyone has an idea where to source the input PIA chips or other things I can diagnose?

Thanks,
-M
 
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Bob Roberts? :) (Smiley as your sig has a link!)

6821 but also check the LS257 at IC3 as player 2 flap goes there before the PIA.



Hahah. I remember reading they were hard to find somewhere. So I hadn't thought about looking at bob.
 
While we are on the Williams board subject, I have a robotron interface board that is stuck on shooting right...what defective IC would cause this?

Thanks
 
While we are on the Williams board subject, I have a robotron interface board that is stuck on shooting right...what defective IC would cause this?

Thanks

does it do it when you have the control panel unplugged? if so, it's definitely one of the ICs on the input board.

thank you tendril for more information
 
does it do it when you have the control panel unplugged? if so, it's definitely one of the ICs on the input board.

thank you tendril for more information



Yep. I've had the control panel completely unplugged and it still registered as Flap #2 is closed.
 
When testing The LS257 - I should be checking the output line on it (pin 9 on the datasheet) to see if it's stuck high, correct?

Hmm, LS257 is a multiplexor so the output pin 9 is probably going to strobe between both inputs (which are flap #2 and flap #1). This might be awkward to test in-circuit. I guess if you have a logic probe you should have a pulse if either flap is pressed, and solid if both are pressed or both released. I'd be more inclined to remove and test in a tester or just shotgun replace it.

You could easily test the input to that chip on pin 11 though and least verify the wiring is ok.
 
Hmm, LS257 is a multiplexor so the output pin 9 is probably going to strobe between both inputs (which are flap #2 and flap #1). This might be awkward to test in-circuit. I guess if you have a logic probe you should have a pulse if either flap is pressed, and solid if both are pressed or both released. I'd be more inclined to remove and test in a tester or just shotgun replace it.

You could easily test the input to that chip on pin 11 though and least verify the wiring is ok.

Gotcha. yeah I noticed both flap 1 & 2 are tied to that output. I'm pretty sure the wiring is fine because flap 2 was stuck down even with the panel unplugged. I'll probably just shotgun it then and pickup both the LS257 and the PIA in the process. I do have a logic probe though.
 
Gotcha. yeah I noticed both flap 1 & 2 are tied to that output. I'm pretty sure the wiring is fine because flap 2 was stuck down even with the panel unplugged. I'll probably just shotgun it then and pickup both the LS257 and the PIA in the process. I do have a logic probe though.



Ok. So I replaced and socketed the pia and the 2 ls257s. Same thing :(
6d349eb68cc5c20eb930303a7f4b270a.jpg
 
don't have one of these in my immediate reach to look, but follow that wire to the input header and then follow the pin through the traces and see which IC it goes to. if it's one of the LS257s that you just replaced (I'm guessing), then go deeper through the circuit to the next point.

I hope to one day figure out the science behind this. I'll need a new logic probe first though.
 
Follow the path from the flap 2 to the LS257; you can measure with a meter. The inputs to the CD4049 IC7 are pulled high by the resistor pack. Pin 7 in should be high and pin 6 out should be low normally. The resistor pack could be bad or the debounce capacitor could be shorted. Press flap 2 and verify pin 7 goes low and pin 6 goes high. Low will be less than 1vdc and high with be greater than 3vdc.

6821, 4049, resistor pack, trace damage, capacitor, LS257 have been my experience as to the most common problems. You can use an A/B/etc. version of the PIA as they are simply faster versions.

Good Luck.

Kirk S.
 
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