I've been trying to diagnose a problem with the racetrack on my Corvette. Last week for the first time that I can remember seeing I got a U6 checksum error so I pulled the U6 chip only to find 2 legs broken completely off the U6 game rom. I thought for sure this was causing my racetrack nightmare problem so I ordered a new rom from Action Pinball. Today I installed the new chip and am still getting the U6 checksum error; my racetrack problem is also still there.

Thinking maybe it was a problem with the replacement Rottendog CPU that is in the game I pulled the factory CPU out of my Dirty Harry, swapped over the newly burnt ROM and security chip only to still be getting the checksum error and my racetrack problem hasn't gone away either.

Any ideas why I started and keep getting the U6 checksum error?

Hi markmon, thanks for the reply and info. I have not tested the game rom and security chip in Dirty Harry. Are you saying I should put the new corvette rom and security chip on the dirty harry cpu board and put it in the dirty harry game and power it up?

Here is the saga of my "racetrack nightmare" any advice would be greatly appreciated, I just updated the thread with what I did today: https://pinside.com/pinball/forum/topic/u6-checksum-error#post-3701692

It's interesting you mention voltage, because I'm wonder if there is a voltage problem causing the racetrack optos to read crazy when in game mode. The game is a re-import and I'm wondering if whomever set it back up for US set the voltages right and how to tell.

I did as you recommended, I installed the CPU board in Dirty Harry with the corvette rom installed, hooked everything up besides the ribbon cable to the power driver board. I did still get the U6 checksum error so it does sound like a bad rom. Did you get a chance to look at the thread detailing what all I've been through on the racetrack? If so any ideas? Any recommendations or suggestions would be much appreciated.

I got a replacement U6 rom from action pinball, no more checksum error, but of course I still have the racetrack problem