[ARC5] R-27/ARC-5 Hookup Question

[Neil]

> Connected normally, the final audio stage B+ does not go through the
> choke. If it's biased Class A, the final stage could draw more than the
> rest of the set. If it idles at 50 mA, the transformer will dissipate 1W
> roughly.

I doubt it runs anywhere near 50 mA. It's connected as for Class A, but
is starved for current by virtue of the high cathode resistor (1500 ohms
if I remember correctly). The 12A6 will deliver 3.4 Watt of audio if
biased at about 35 mA, which implies a cathode resistor of 390 ohms.

With headsets and even in a noisy aircraft, the 12A6 is never called on
to deliver more than a few dozen milliwatts.

73 de Neil ZL1ANM