This is the first I've heard of this on a DVR. Who was the
manufacturer?

wrote:
Do not forget that some DVRs like the HDTV sets have the tamper
switches on them which will render the unit inoperable if power is
applied with the cover off.

I took one apart that was already on the curbside only to find out that
someone prior to it being thrown out had taken it apart with the power
cord plugged in. The cost to send it off to be "re-coded" by the
manufacture was more than 50% the cost to replace the unit!!!!