"tjbitt" wrote in message
oups.com...
Thanks for the suggestions. I ordred an rca adapter plug today. Do I
need the jumpers for mute PTO lamp etc if I'm using the R4C as a
receiver only ---no connection to transmitter? Hate to be a dummy but
these older radios are completely new to me. Thanks agn for the
help---Ted --KQ4MZ

I would get a good copy of the manual you need - Bob Sherwood has good
copies as well as a couple of the other manual suppliers (be selective).

BTW, there were 4 major changes during the Drake R-4C production run.

Wayne Montague, VE3EFJ compiled this information (below) and believes it to
be accurate, BUT not necessarily a complete dossier on the Drake R-4C
changes over its entire production run.
This is his latest update.
a.. R-4C ser no above 16121
Revision date - Feb 1973
All mixer tubes 6HS6. First and 3rd mixers cathode injected. Second mixer
is a dual gate MOSFET. The IF chain following the first crys- tal filter is
6BA6 1st IF, Noise blanker and then 2nd mixer. 4 posi- tion filter select.


b.. R-4C ser no above 18726
Revision date - March 1974
All mixer tubes 6HS6. First and 3rd mixers cathode injected. Second mixer
is a 6BE6 with a JFET (2N5949) buffer. 5 position crystal filter selection.
3 diodes in series across the S Meter to compress the meter range. 2 S Meter
zero pots were employed - one internal and one external.


c.. R-4C ser no above 21000
Revision date - Nov 1974
All mixer tubes 6EJ7. First and 3rd mixers grid injected. Second mixer is
a 6BE6 with an JFET (2N5950) buffer. 5 position crystal filter selection.
Some intermediate models in this transition period may not have installed
the new tapped IF transformer, T7C.


d.. R-4C ser no above 25900
Revision date - Jan 1976
All mixer tubes 6EJ7. First and 3rd mixers grid injected. Second mixer is
a 6BE6 with an JFET (2N5950) buffer. 5 position crystal filter selection.
T7C IF transformer. Very little electronic difference to the above model
except a 125 volt zener diode at the junction of R12 and R13 (regulated B+
to the plate of the 6BE6 mixer).

This could be the latest model in the series before production was halted.
From the schematic, the differences between this model and the 21000
previous is little.