I've got a N52t on the bench right now. Customer had someone tell him it had to run off 220v. Its been working with 120vac for a while. I don't see a problem as long as voltages are correct/corrected. Any issue running off 120v vs 220v? Schematic says both!
The N52t is by no means a “universal voltage”-design as you often find with todays switched mode PSU’s.
The schematic even shows, there’s no 2nd tap on the transformer to switch to the other mains voltage.
So, it’s either 117 V or 220 V.
Running a 220 V model on 117 V just won’t work.
Running a 117 V model on 220 V (or todays EU 230 V) overvoltage would at least blow the fuse, or break the PSU.
As Klaus mentioned, calibration is mandatory and denoted in the schematic.
Both, anode and heater voltage are regulated in the t-model.
Anode V by the Zener GR3, heater V by the active two-transistor circuit.
So, once calibrated, output voltages are independent of mains voltage variations within reasonable range.