As mentioned in the TechStep documentation, it has a quick self diagnostic routine that’s run every single time you flip the switch to the ON position. So if there was something seriously wrong with your TechStep, it should, in theory, show some kind of special message on the LCD at start up.
The only thing that could possibly cause damage would be if something inside the text app or short circuited, but in that case, again, I would think you would see an error message when you turn on your TechStep.
With that said, I have never plugged either of the serial cables into either of the ADB connectors on the Mac or vice a versa. I also never tried pulling out and inserting cables when both the TechStep and Mac were turned on, and such is specifically mentioned in the documentation as something you definitely do not want to do.
The only other thing I can think of is that it could be a cable fault, especially if it’s that big thick SCSI cable. again, the only thing I can think of that would consistently cause damage to a machine is if something externally was causing an electrical short to occur on your motherboard. But I would assume you should be able to see at least some burn mark on the motherboard with a magnifying glass in that case. Maybe not, I don’t know. Some shorts can’t happen without showing any physical burn marks and yet the chips that were shorted are dead.
I’m very sorry to hear this has happened to you. In all honesty, that is the first case I have ever heard of a TechStep potentially having damaged the Macs it was trying to test!
