>In the early broadcast days, when broadcast power
>could only be achieved by running many tubes in
>parallel, it was common to have "reasonably" separated
>feed systems for the tubes.
>
>The power supply had to be stiff enough to feed all
>(sometimes 16) of the anodes in parallel. An arc or
>other fault in one tube, therefore could suffer the
>entire current capability of the large power supply.
>This huge current surge not only could destroy the
>tube that arced, but if that tube's parasitic
>suppressor could not handle the entire power supply
>current, the suppressor would be vaporized as well.
** A typical parasitic suppressor's inductor has 0.0005-ohms to
0.03-ohms of DC resistance. The stock parasitic suppressors in a TL-922
will carry 50-amperes DC 24/7. Vaporizing parasitic suppressors with DC
seems a bit unlikely.
>
>The separation method involved using a separate
>current-limiting resistor per tube, the far side of
>which got its own bypass capacitor, then feeding the
>anode choke for one tube. Each tube had to have its
>own DC blocking capacitor, else all 16 feed networks
>ended up in DC parallel anyway. The benefits all
>arose from considerations of DC and arc current, and
>there were articles written about how to do the
>multiple feed network without causing instability. In
>other words, in the days when it was commonly done, it
>was known to have drawbacks.
>
>In current designs, there's a separate suppressor per
>tube already. One could design the amp with only one
>suppressor, but I've not seen it done for a long time.
>
** the 30L-1 used 1-suppressor per 2-tubes. I have heard about squirrel
infestations therein, especially with current production 811As. Seperate
suppressors reportedly helps.
>In a two-tube ham amp, it's hard to imagine that
>there's a benefit to be gained. You're basically just
>adding another anode choke and bypass capacitor per
>tube. But there is a potential drawback. If the two
>anode chokes couple to each other, it is possible to
>create a tube-to-tube feedback mechanism,
** been there, done that. No exciter is needed.
>the results
>of which are not likely to be desireable.
>
>73,
>
>Dave W8NF
>
>
>>kenw2dtc wrote:
>
>>> I want to build a grounded grid amp with two
>triodes in parallel.
>>> Would there be a problem if there were two separate
>sets of plate
>>> chokes and suppressors and glitch resistors and
>combined the RF
>>> output of the tubes by connecting both plate
>coupling caps to a
>>> common point at the entrance to the pi-network?
>
>To which Vic K2VCO replied:
>
>>Probably not, but the really interesting question
>>is "why?"
>
>>Vic K2VCO
>
>
>
>__________________________________
>Do you Yahoo!?
>Free Pop-Up Blocker - Get it now
>http://companion.yahoo.com/
>_______________________________________________
>Amps mailing list
>Amps@contesting.com
>http://lists.contesting.com/mailman/listinfo/amps
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|