Joust Flap Button Not Working (Board Issue)

nutballchamp

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Player 2 Flap isn't working on my Joust. I put the game in switch test, took off the connectors on the Interface board and jumpered ground to the player 2 flap pin. Nothing. I got my logic probe and checked for a pluse on IC7 pin 7 and got a low pulse when closing the flap switch. I swapped out the interface board with my Robotron and still not working. I guess the problem is on the CPU? I don't understand the schematics enough to locate the problem any further. Please help, thanks.
 
I've fixed control panel problems by replacing the CPU processor. you could try reseating it first. If you have another to swap in, try it...
 
Ok, I just tried swapping my Robotron CPU (6809E) with Joust. Still no player two flap. Any other chips I should test with my logic probe? Thanks.
 
If you have a spare I/O card or can borrow theone from you Robotron, swap that one in first. Most of those problems occur when the interface chips go bad or the PIA goes bad. It is pretty easy to diagnose and replace the correct chip.

If you have a logic probe trace the line in the schematic until it hits one of the interface chips. Flap 2 goes to IC7 (4049 CMOS Hex Inverter) pin 7. The output is on pin 6. If you put your logic probe on pin 6 you should see the state is the reverse of the state on pin 7 and if you press the flap button you should see the state toggle.

If that works the next stop is IC3 (74LS257 Quad Data Multiplexer) pin 11. If IC3 is working you will see the state change on one (ormore) of the output pins (4,7,9,12). If these change correctly, then it is probably the PIA (the big chip).

It is a lot easier to see if you have a working one to look at to compare.

ken
 
Thanks so much for the help on understanding the circuit. I used my logic probe for the first time and can't wait to go back in tonight. I'll try swapping out the CPU board if the Interface seems fine.
 
That's why so many of the pieces of the Williams games were interchangable. OPs had to stock fewer spares. If a machine was down, just pull a CPU board out of the bag and swap it in. Not the CPU, try the I/O board. Pull a blank ROM board out and swap in the chips.

The CPUs were interchangeable from Stargate through Sinistar (plus Blaster and Splat!). I/O cards interchanged from late Defender through Bubbles (Sinistar had it's own I/O card) plus Splat!. ROM cards were a little different there were 5 ROM cards Defender, Stargate, Joust/Robotron, Bubbles, Sinistar, Splat! (same as Joust but with SC2 chips) (don't remember about Blaster).

So most debugging was done by swapping in the field and then fixing back at the shop. With other manufacturers boards you had to stock the whole board and BITD they cost almost as much as a new cabinet. That's why when these pack rat operator's heirs clear out the warehouse there are often a lot more boards then cabinets. Some of those were repair stock.

ken
 
I took another pass at this and still no go. I swapped out both my working Robotron CPU and Interface pcb with Joust. With both Joust boards and Robotron, I never got a signal from IC7 pin 6 when closing the flap switch (jumpered ground and pin 4 with the input connector off). Tested this on other buttons with the corresponding pins and was getting a signal. I also reseated all the roms and reflowed solder on the rom board headers (and all other boards). I noticed that when the Robotron interface board was in Joust, the Flap 2 button was always closed. Could it be a bad rom? Crazy, it could be this complex!
 
Yea, continuity from the switch all the way to the connector on the board. I've been working with the connector off and jumping ground and the flap 2 pin when testing.
 
i had this happen also and after hours of doing the same stuff you did i found it was a bad ground..id check all the ground wires from the cp to the board.. hope this helps good luck
 
I meant continuity across the switch. As in you push the button and your meter shows it as closed?

Or perhaps I just didn't understand your explanation....
 
I meant continuity across the switch. As in you push the button and your meter shows it as closed?

Or perhaps I just didn't understand your explanation....


Yea, there is continuity when the switch is closed. I was thinking if the connector is off and you just jumper the pins when you want the button pressed then you eliminate any cp problems. I'm able to control all the other inputs this way.

Funny that I had no problems fixing the reset problem just before trying to fix this.
 
When in doubt try things upside down. Put the Joust I/O board in your Robotron. If you can move left (3J2-4) then it is not the I/O card. Connector 3J2 pin 4 (3J2-4) is Flap #2 in Joust and Move Left in Robotron. If it works in Robo, it is not the I/O card.

Then that leaves the address lines and decoders on the CPU board.

ken
 
When in doubt try things upside down. Put the Joust I/O board in your Robotron. If you can move left (3J2-4) then it is not the I/O card. Connector 3J2 pin 4 (3J2-4) is Flap #2 in Joust and Move Left in Robotron. If it works in Robo, it is not the I/O card.

Then that leaves the address lines and decoders on the CPU board.

ken

I just tried this and it works in Robotron but realized that 3j2-4 in Robotron is not used, as that's move left #2. 3j3-3 is move left #1 which is what player 1 move left is wired to.
 
I just tried this and it works in Robotron but realized that 3j2-4 in Robotron is not used, as that's move left #2. 3j3-3 is move left #1 which is what player 1 move left is wired to.

Sorry, you're right. I was going off one of the crappy PDFs of the manuals when I was at work. Rats!

ken
 
I just figured out I didn't have my logic probe hooked up correctly. I was powering it on across a 13v cap on the sound board. Manual said it need to be powered with less than 20v so I figured it was alright. I hooked it up to the I/O board across a small 5v cap and I'm now getting "low" readings on some of pins. Before it was "high" readings on all pins. I'll troubleshoot again tonight now that I know how to use my probe. Thanks for the help.
 
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Got it working. Pretty easy to figure out once I hooked up my probe correctly. IC7 pin 6 wasn't changing to high after ground pin 4 (flap 2). I replaced IC7 and it's now working. Thanks everyone.
 
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