Push Pull Power supply. to Tube or not to?

[hacknet]

i thought chokes make it worst?

 

[Eli Duttman]

Is there someway to cure the turn on surge?

There a number of techniques you can use. A hybrid bridge using indirectly heated heated vacuum diodes is excellent. Vacuum damper diodes are nice because they turn on very slowly and exhibit a relatively low forward voltage drop. A 2nd technique is to use negative temperature coefficient thermistors. Jim McShane puts NTC inrush current limiters into H/K Cit. 2 amps. Without the NTC devices there is a bang from the power trafo at turn on. Add the NTC parts and the bang goes away. NTC thermistors provide only a few seconds of protection, but that is enough in an amp with a bias supply.

 

[DrDeville]

I regretted my choke idea almost as soon as I posted it
Putting a choke on a choke is perhaps not particularly inspired.

Thanks for the negative temperature coefficient thermistor
suggestion. Now for my flurry of questions:

Would it make sense to put them on the HV secondary?

Is their residual resistance when "on" significant, compared
to the HV secondary's internal resistance?

Put another way, how does a good NTC's voltage drop
under load compare to a good vacuum damper diode's
forward voltage drop?

Can you suggest a part/source?

Thanks for your guidance,

George Ferguson

 

[Eli Duttman]

Thanks for the negative temperature coefficient thermistor suggestion. Now for my flurry of questions:

Would it make sense to put them on the HV secondary?

Yes, that's where Jim McShane puts them in the Cit 2.

Is their residual resistance when "on" significant, compared to the HV secondary's internal resistance?

Put another way, how does a good NTC's voltage drop
under load compare to a good vacuum damper diode's
forward voltage drop?

A properly sized NTC part has a very small insertion loss hot. For vacuum diodes, the forward drop in dampers is small, say 15 V. NTC devices do NOT provide protection if the unit is turned off and back on quickly, while IDH vacuum diodes do.

Can you suggest a part/source?

Mouser (www.mouser.com) and Allied (www.alliedelec.com) carry NTC devices. Thermometrics is a brand.

 

[DrDeville]

Thanks Eli!