1936 RCA RR-359B Restoration

[bandersen]

OK, how about that tuner?
As mentioned earlier, the mixer is on the mains chassis. There is also no active RF front end.
The only active device on the tuner is a type 76 tube used as the local oscillator.
It is continuous with three ganged capacitors. Tuned antenna, mixer and Hartley VFO for the LO.
Those coils are wound next to each other on a common form for coupling.
Dead simple and badly radiates the LO back through the antenna!

Darryl to the rescue once again


Here's the schematic from the original "A" version.
Note the use of an experimental A-305A tube. Mine is missing, but a 6D6 may work well enough.


Later revisions used a rotary switch 6J5 and 1852.
Big thaks to Dave AKA "streetmechanic14" for this photo


Very similar to the Meissner design.


I'm going to experiment with a ganged cap salvaged from a Hallicrafters shortwave radio with similar range to the original.
Not necessarily going to be the final tuner I use in the set, but I figure it will be fun to try and get something going.


Darryl also kindly identified the parts in the photo using designators from the schematic. This will be a big aid.
L1/2/3, L45 and L4 are the coupled coils wound on a phenolic form.
I'll also examine one in person at the Early TV museum soon.

[Mr Hoover]

I'm surprised they didn't use RCA acorn tubes/valves in the
tuner,these were developed by RCA and available by the mid
1930's.Performance would have been way better.954 955 956
series
https://en.wikipedia.org/wiki/955_acorn_triode

[Penthode]

Originally Posted by Mr Hoover

I'm surprised they didn't use RCA acorn tubes/valves in the
tuner,these were developed by RCA and available by the mid
1930's.Performance would have been way better.954 955 956
series
https://en.wikipedia.org/wiki/955_acorn_triode

I agree. I have an RCA frequency calibrator from 1935 which used the acorn triode 955. And a 1939 Hallicrafters S27 UHF radio which uses the pentodes. Maybe 1935/36 was a bit too early?