Later models had a disabling microswitch when you opened the case.
"This then made it difficult to work on the insides of the PC when it also needed to be powered up."
Pfft!
I have this exact same set-up and need to see the works in action with the lid off on my antediluvian clothes dryer and I figured out how to jumper the switch even when the panel containing it was removed in seconds, and built a reusable jumper to do the job in minutes. I guess they didn't have wire and crocodile clips in your "shop".
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Biting the hand that feeds IT
