So I picked up an arm wrestling machine called the Grappler in barn find condition. Unfortunately I don't have any paperwork on the game. It boots, gives me a few error codes on the display, then the hydraulics kick in and move the arm all the down and it goes into attract mode. It looks like the board itself is missing a few components. A manual and schematic would be a lifesaver for this one. I figured I could try and shotgun some parts to get it to work but unfortunately with a few parts missing that is going to prove impossible.

Armwrestling Amusement Devices. The Best Machines in the Arcade-1 (resized).JPG

The struggle is real on this one. I traced the circuit by hand. I replaced the weight selector potentiometer and now I can select the weight class on the display. Other than that I haven't made any progress. The game seems to be shorting out during gameplay. I'm not sure what is causing it. I dumped the rom from the game but unfortunately have no way of testing it. I'm going to trace all the wiring this weekend and see if I can find any shorts. It's so hard trying to repair a machine with almost zero documentation.

Ok so I'm narrowing down the issues on this one. I just wanted to document what I've done so far just in case others are trying to fix one of these and need help.

1. I noticed the weight selector potentiometer wasn't working and the game would constantly be set to over 500lbs. I found someone on the maaca forum that actually owns one of these and told me his only goes up to around 350lbs. I just put in a 2k pot that I had laying around and it adjusts from 0 - 450 now. I'm not sure if that is correct. At this point the game would boot but would give me error code 8, 6 and 9. When I coined up the game the timer would start and I could adjust the weight class but the moment I pressed the elbow pad the game would kinda short out and just make a buzzing noise and the arm wouldn't move. This is odd because the arm would move when the game initially booted up.

2. Since I have no schematic I drew the motor driver circuit on a piece of paper to see how it should work. I also traced the traces and tested the components as best I could with just a multi meter. This section of the circuit seemed to be ok.

3. I noticed the voltage coming out of the 7805 voltage regulator was around 4.6v which is pretty low in my opinion. I decided to install a new one since I had one laying around and that brought the voltage up to 4.98v measured at the eeprom. After getting the voltage higher the game would still do exactly what it was doing before.

4. I dumped the program on the EEPROM and was lucky enough to acquire a copy of the file from John Robertson and compared my file dump with what was on my rom and confirmed the chip was corrupt. I erased and reprogrammed the chip with the known good software and my game now doesn't boot . - I replaced the socket and reseated the xc68hc11a1fn microcontroller for good measure and the game doesn't boot. I've sent an email to John Robertson just to confirm the file he sent me was a known good file just to double check.

5. I've also ordered a new 27HC373 and 27HC374 data latches for the bus which I will shotgun in if need and also a new microcontroller. I believe it has to be one of those three components causing the issue. I might draw out the circuit for the data latches and microcontroller if I have some time this weekend but that's a lot more work than just replacing the components so we'll see. But since I couldn't locate a schematic for this game, I might do it just to help out future people in my position.

6. I watched over the top last night to inspire me to continue getting this beast working!!

I'll continue to update once my parts come in.