RadioBanter - View Single Post - Power Mod for AN/GRC-9

October 30th 03, 05:27 PM

In article ,
(Ron) writes:

But it works!! the 1.4volt heater has lead me astray, seems its
not 1.4volt but actually 3volt? the 3A4's in the Tx have a tapped
filiment I think, working a bit in the dark here, anyone else familiar
with these old beasts??

I still don't know if we're talking about the same radio -- mine has a big cast
dial with adjustable tab stops around it, and was half of a Tx/Rx combo in one
case. If I knew where to look, I'd go check its model number :-)

But ISTR that in mine, the heater is indeed 3V, and the 8-plus tubes are wired
in parallel-series. Four 1.4V tubes in parallel, in series with the other
four, and the 3V tubes wired across the whole thing, maybe with their center
tap connected to the "floating" junction of the two parallel strings. But
don't take my word for *anything*!

The usual trick when dealing with a 3V tube, when running from 1.4V source, is,
as you know, to power both sides of the filament and ground the center tap.
Hope this helps -- Mike K.

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