[Amps] switching power supply for tube amplifier

[Hsu]

Actually, some microwave oven was using switching PS.
Maybe we can find a very good switching PS in it.
  I think the switching power supply will be more popular in tube
RF amps.In 1990s, most of  Chinese TV and broadcasting station use 
 switching power supply for  the filament of transmitting tube.
but now most of them was replace by solid state transmitter.
    I just got a micrwave oven transformer, I have test it in no load, I found a 
problem, even work in no load, the transformer is very hot few minutes later,
 So I'm  doubtful of its  capability of work in continuous condition.I have read 
an article in QST about using microwave oven transformer in parallel connection 
as HV power supply, anyone using silmar PS?how about working?
 my transformer's weight is 5.2kg  Could someone can tell me its CCS rating?
      73!Hsu