Problem with a Super Off Road, 2 player

[lkench]

Hey all, I recently bought a Super Off-Road 2 player version at auction.  I think I got a pretty good deal, but there is one problem with it that's bugging me.  When I press the bule player gas pedal, the game registers that the red player gas pedal is pressed too.  I also noticed that in the diagnostic screen, pressing the red pedal registers both red and yellow (apparently there are just slight modifications for the two player version and both the two player and three player versions use the same diagnostic code) and the blue pedal registers all three.

I've replaced a the two chips that appear from the schematic to control which pedal input is read at any given time (an 8 bit multiplexer and a flip-flop).  I don't think there's anything wrong with the A to D converter as it does change values as I press the pedal further.  I also noticed that the unused inputs were just allowed to float.  Generally that's bad, so I tried grounding them.  That fixed the problem of the yellow pedal (which in the two player version I obviously don't have) from getting detected, but still, when I press the blue pedal, the game thinks I pressed the red and blue pedals.  It never goes the other way though - that is, when I press red, it only registers red (since I've grounded the yellow input).

What I really would like to know is if anyone else has had this problem with this game.  If so, was it really something broken or is this a design problem?

Thanks,
lkench

[Ken Layton]

Doesn't this game have a dip switch to select the type of cabinet, like 2 or 3 players?

Are the gas pedals wired correctly? No broken wires from the pots? I saw one once where the setscrew on the pot shaft was loose

[pcates]

Did you trace all the wires?? It sounds like they may be crossed somewhere along the lines.... Use a multimeter and check for continuity from the switch to the board connector. If there is continuity from the blue to red they are crossed somewhere. Easy to fix when you find it. If they both come down clean then it may be in the board. Much more difficult.... Good Luck,
Patrick

[lkench]

First off, it is behaving correctly as a two player game - it's just it appears the diagnostic screen is the same for both 2 player and 3 playerl, so I don't think I have a dip switch problem.

If the problem was as simple as bad wires, wouldn't I get both registering regardlessw of which I pushed?  When I push the red pedal, it just registers the red pedal.  It only registers both when I push the blue pedal.

I assume then there is something wrong with my boardset, and this isn't a known design problem with this game.

It's still mostly playable though since in typical gameplay, you just stand on the pedal and go though 

[lkench]

So, I got out the oscilloscope and it appears to be a timing issue.  If anyone has one of these games (two or three player), could you tell me what chip is located on the top board at U80.  Mine has a 4051, but the silkscreen on the board says it should be a 74HCT4051 which I know to be a bit faster.   Just looking for something...

Thanks,
Larry

[lkench]

In case anyone else has this problem, I finally got it fixed.  It turns out, it was just dirty pots.  I took the pedals out, removed the pots, took off their covers and got out the meter to make sure they were doing what they were supposed to.  After spinning them through, they seemed to be working fine again.  I put everything back together and all works as expected now.  The only thing is the diagnostics screen still has the yellow player pedal bouncing around and following the red pedal, but that appears to be the design of the pedal input circuit.  Since nothing is hooked up to the yellow pedal, that's what it does.  And that's why the red and blue pedals bounced around and followed each other when the pots weren't working right.

Anyway, I'm happy now and now feel like it might be worth putting more money into restoring it cosmetically now that the game is back to working 100%.

-lkench