[ARC5] AN/ARC-5 R-23 Question

[Mark K3MSB]

Back in August I picked up an R-23 Navigation receiver.   I was delighted
to find this as I do NDB hunting and wanted to play with this receiver on
the LF band a bit this winter.

Externally the radio was in nice shape with original connector on the back.
  I removed the bottom cover and immediately saw modern wiring.  Lots of
it.   Oh crud....

The first thing I did was to check the filaments and, as expected, they
were wired for 12/14 volts.  No problem there.

The thing about the new wiring was that is was very nicely done, not your
typical hack job you find in these radios.     I did some preliminary
circuit tracing and it looks like some of the new wiring just replaced the
old wires.

I am using AN 16-30ARC-2 dated 15 Dec 1954 as my reference manual.   It is
of course a copy from the web.

I note in my R-23 that C-30 is insulated from the chassis, and the
capacitor case goes through a 100K resistor to ground.

In AN 1630ARC-2, Figure 6-3 (page 56) shows the underside of the radio.
It looks like C-30 is raised from the chassis – but since my manual is a
copy,  all I see is black in that area.   Can any of you verify it is
lifted / insulated from the chassis?

Also, at the top of C-30 are 4 resistors (R4, R9, R11, and R-27).  My R-23
has a 5th resistor in that group, and that 5th resistor is the 100K that
goes from the case of C-30 to ground.    The 5th resistor is original – It
wasn't added later.

My Figure 6-3 says it's of an early production set.  The schematics in the
manual show the case of C-30 directly grounded, but I assume that is also
for an early unit.  If any of  you have a different copy of the manual, can
you check the schematic for this?

Thank you & 73

Mark K3MSB
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