No power

As a former electronics technician the first question is always, are all the connections solid and is it plugged in.
I am sure you have checked these but it is the first place to look.

There also might be an internal fuse that would probably be very easy to see if you removed the cover....or a fuse hidden in the power connector.

Look for the obvious....you will catch 90% of the problems...

A TGS200 that's lasted this long?????? You're very, very lucky indeed.

When I worked on these things many, many years ago, common failures were in the HV power supply. But by now it could be anything . . .