Re: tube-noob question

In message <f4pisq$3vn$1@xxxxxxxxxxxxxxxx>, Scott Dorsey <kludge@xxxxxxxxx> writes
Ross, NS7F <rjtucke@xxxxxxxxx> wrote:
In a circuit with two 6.3V tubes, can I just series the filaments so
that I can use a 12-13.8V supply? Or are there subtleties that I'm
missing?

You can, but the tube filaments won't last as long because of the turn-on
surge. If it's a circuit where the tubes fail with poor emission long before
the filament fails, that's fine.
--scott

I don't get it. Maybe I'm a bit thick, but why would the turn-on surge higher? Provided the filament current is the same for both tubes, I wouldn't have thought that it would have made any difference. In the good old days, I'm sure that I have connected up 12AX7/12AU7/12AT7 heaters (12.6V centre-tap) to run off 12.6V (pinout = anode-grid-cathode-heater-heater-anode-grid cathode-heater CT). Would the switch-on surge be less if they were run connected for 6.3V?
Ian.
--

.

Relevant Pages

  • Re: Surge protector
    ... But the surge only selects one circuit and pretends other ... a surge protector magically absorbs what three miles ... Effective protection earths those thousands of joules harmlessly ...
    (rec.gambling.poker)
  • Re: AC Power filter and phone line filter (homemade circuit breaker)
    ... Do you think that tiny circuit will stop what three miles of sky ... Notice the ground wire simply carries the surge completely around ... And other components divert that surge energy into the ... Internal appliance protection assumes that surge energy ...
    (sci.electronics.design)
  • Re: AC Power filter and phone line filter (homemade circuit breaker)
    ... Do you think that tiny circuit will stop what three miles of sky ... Notice the ground wire simply carries the surge completely around ... And other components divert that surge energy into the ... Internal appliance protection assumes that surge energy ...
    (sci.electronics.design)
  • Re: Surge protector
    ... But the surge only selects one circuit and pretends other ... a surge protector magically absorbs what three miles ... Effective protection earths those thousands of joules harmlessly ...
    (rec.gambling.poker)
  • Re: Fastest AC Electronic Fuse
    ... Shunting the load to burn a fuse on the AC line would be ok too.. ... Load: The load on the line is not a transformer and is not inductive. ... Surge rate: guessing 45Amps in 1uS ... The load circuit has a power bridge rectifier. ...
    (sci.electronics.design)