[Drake] Head-scratcher R-4B

[w7fe]

Hello Group,

I have an R-4B that's a real head-scratcher. Here are some of the goofy 
things I've observed:

1. No chassis markings..no triangle QA ink stamps, no labeling of the jacks, 
tubes, or trimmers. Some coil cans are marked (50KC IF, filter match, etc.).

2. Passband tuner is open frame, no can over it like on other R-4B's. Tuning 
shaft operates a butterfly cap, not the coil slugs. I don't have an 
R-4A...maybe this is from that design.

3. No 5595 KC crystal in the V3 second mixer circuit. Only R10 (150K) to 
ground from the grid and a coax which goes up thru the hole where the C61 
piston trimmer should be and disappears under the passband tuner (can't see 
where it goes without some disassembly).

4. An extra board is mounted between the two boards behind the AVC switch. 
This board has a 5644.999 crystal on it, three transistors, a diode,a big 
RFC, and many other R's and C's.  Circuit side of board says 'R-4B Osc-Mix'. 
A piston trimmer is mounted in the chassis near TP-2 and connected to this 
board. I expected that adjusting this cap would pull this 5645 KC oscillator 
to net with my T-4X when transceiving, but it has no effect.  The TX and RX 
freqs are different by about a KC. Have to operate separate and talk the 
T-4X on to the receive freq.

5. Probably an unrelated issue: I can only get to about
-2.25V at TP-2 with R111 (RF Gain) and R87 (Rcvr Sens) pots at zero ohms. 
With AGC off  it goes to near
the specified -1.35V. S-meter therefore reads low as the circuits fed by the 
AGC lines over-biased and cut back.

Is this thing weird or what? Has anyone else ever seen an R-4B anything like 
this?

Comments? Conjecture? Questions?

My best guess is that it's a lab prototype, but a fellow who worked at Drake 
told me that those never left the factory. He did say that Bob Drake allowed 
the employees to buy parts and build their own rigs at home, but he said 
that he was the only guy he knows of who ever did that, and he didn't build 
one like this.

This sure is a candidate for "...things that make you go Hmmmmmmm..."

73 de Stu W7FE
Phoenix