[ARC5] R-392 B+

[Meir WF2U]

Another 28 VDC primary power aircraft transmitter-receiver also uses
"standard" high plate voltage tubes at 28 VDC plate voltage in the receiver
section with the exception of 2 tubes. In the Collins 18S-4 HF TX/RX the
tube complement of the receiver is 2 x 28D7 dual beam power tube (rated for
28VDC plate voltage) - one as the high frequency oscillator and the other as
the audio output amplifier. The rest of the tubes are 6BA6 RF amplifier,
12BE6 mixer, 3 x 6BA6 as the first, second and third IF amplifiers, 12AL5
noise limiter/AGC, 12AU7 audio driver and CW sidetone oscillator, 12AU7 BFO.
The transmitter section is basically the ART-13 circuit, with a 12AU6
crystal oscillator instead of the 837 VFO as in the ART-13. Only the
transmitter section gets high voltage, from the built-in dynamotor,
identical to that in the DY-17A/ART-13.

On the other hand, some R-392 owners feed the filaments and the plates
separately, because some claim that the receiver performs better with around
36 VDC on the plates, instead of the specified 28 VDC.
I haven't seen any performance measurement result with 36 V plate voltage,
and I'd never inflict that on my R-392's...

73, Meir WF2U
Landrum, SC

-----Original Message-----
From: arc5-bounces at mailman.qth.net [mailto:arc5-bounces at mailman.qth.net] On
Behalf Of Robert Eleazer
Sent: Sunday, March 10, 2013 10:26 AM
To: arc5 at mailman.qth.net
Subject: [ARC5] R-392 B+

My impeccable reference source  (Fair Radio catalog from 1973) says the
R-392 has 25 tubes consisting of 26A7, 26A6, 12AU7, 26C6, and 26D6.

So my answer to your question would be "Yes."

You have tubes that are designed for HV B+ (12AU7 and 26A6) and others
probably never used for anything but LV B+ (probably 26D6) but with the
right dropping resistors will work on B+.

Wayne 

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