Terry did an awesome job diagnosing Guido and getting it to function again. The power supply on the laptop had been blown. He cobbled together a new one as a temporary solution but a permanent replacement is still a necessity. Per Terry's post to the listserv, we're on the hunt for a power supply for an older Inspiron 8200. The current supply should be used for charging only with the laptop off/sleeping. Unplug it before powering up the laptop and run it on battery power only. Terry also found loose connections on the board so fixed those as well. We still don't yet know why the power supply on the PC blew. The controller does provide optical isolation for some pins but there may still have been some other spike sent back up the line.
He also pointed me to the working EMC2 config file and I'm using that to rebuild a new GRBL config and firmware. Turns out the pinouts were matching but the timing of the step and direction signals was waaaay off. So kudos to Terry for getting the diagnosis right and teaching me how to improve my debugging skills. Guido also has a new handheld pendant for manual movement but pinouts don't match (shocker!) so we need to debug the DB15 connector and rewire the jumpers. Terry has posted his findings to the wiki and I'll provide updates shortly with all the GRBL changes.
This lesson also gives me hope for the big CNC router because the behavior I saw on Guido with GRBL was similar to the behavior on the big CNC with GRBL. One axis moved albeit with a lot of vibration and the other axis made a lot of noise but moved not a whit. I've posted to CNCZone to requesting anyone to share a working EMC2/Mach3 config file. Because a datasheet for the main IC hasn't been located, we've got no easy way to reverse engineer the signal timing. Next step is to try with an oscilliscope to monitor the motor signals and trace the signals all the way to the IC from all inputs and outputs.
Finally, a big thank you to Sky and concrete Aaron. Sorry, Aaron, I've not managed to learn your last name yet, I promise to do better! Sky volunteered to help trace all the connections from the DB25 back to the controller box. He and I were able to verify all the parallel port pinouts. Aaron volunteered and did a really great job cleaning the sprocket rail on the gantry. It made a huge difference to the point where I can move the Y belt by hand with a bit of pressure. I have no idea how long you spent cleaning the beast but thank you! If anyone else wants to help with the machine, there are several workplans on the CNCRouter page: http://wiki.acemonstertoys.org/CNCRouter. Jump in and let us know what you're tackling!