08-31-2018, 02:58 PM
Hi Bob,
<But...I'm confused...
I didn't realize we are from the same state[Image: http://philcoradio.com/phorum/images/smi...on_eek.gif]
<36, 37, 38 and 39 tubes (a 38 is included in the article example) have DC heaters don't they??
No. They can be use with both ac or dc. The short answer is that a tube w/a cathode can use both a tube that doesn't have a cathode (aka directly heated) only use dc.
> Capacitive voltage drop circuit yields an AC voltage.
Correct as long as the input voltage to the cap is AC.
> Or can they run on either AC or DC since the radio schematic sure looks like the heaters would be AC if you used AC line voltage.
Yes you can! BUT only a resistive dropped will drop the ac or dc voltage by the same amount. You could use a resistor and a diode as the dropper. Will work w/ ac applied to it but if you apply dc to it depending the polarity one way tube won't lite at all. The other way the diode will conduct full on w/o any drop. You can get abt a 40v drop across a diode.
A capacitive dropper w/dc on it I would think it won't conduct so the heaters would lite at all.
Hope this answers your questions.
<But...I'm confused...
I didn't realize we are from the same state[Image: http://philcoradio.com/phorum/images/smi...on_eek.gif]
<36, 37, 38 and 39 tubes (a 38 is included in the article example) have DC heaters don't they??
No. They can be use with both ac or dc. The short answer is that a tube w/a cathode can use both a tube that doesn't have a cathode (aka directly heated) only use dc.
> Capacitive voltage drop circuit yields an AC voltage.
Correct as long as the input voltage to the cap is AC.
> Or can they run on either AC or DC since the radio schematic sure looks like the heaters would be AC if you used AC line voltage.
Yes you can! BUT only a resistive dropped will drop the ac or dc voltage by the same amount. You could use a resistor and a diode as the dropper. Will work w/ ac applied to it but if you apply dc to it depending the polarity one way tube won't lite at all. The other way the diode will conduct full on w/o any drop. You can get abt a 40v drop across a diode.
A capacitive dropper w/dc on it I would think it won't conduct so the heaters would lite at all.
Hope this answers your questions.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got it!
Terry
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