[Milsurplus] BC-1206 and its kin (R-76/ARR-13 Power)

[Mike Morrow]

Jack wrote:

> ... anyone have a schematic for the R-76/ARR-13 receiver?

I wrote:

>Chesson says that it is a **12** vdc unit.  Chesson lists the "RCA AV-126"
> with it, which presumably means that the AVA-126 vibrator supply (which
>can be set for 12 vdc input) was used to power it. ....


I just checked my R-76, and it is indeed connected for **12** vdc operation.
The filaments of all five 14-series loctal tubes are in parallel.  Don't
apply 24 vdc to this one!

It is now very apparent why this set requires a HV supply, while the BC-1206
series used 24 vdc for B+.  Applying 12 vdc to the plates just wouldn't cut
it.  Those 12 vdc B+ "space charge" submini tubes used in late 50s car
radios were still well in the future.

A quick comparison of the BC-1206-C schematic to the R-76 wiring shows the
circuits are very similar except for the 278 kc button, and the fact that
the on-off switch simply grounds one side of the tube filaments and pin 2 of
the power plug.

Power plug functions are:
Pin 1   Ground
Pin 2   Power switch grounds this to pick up remote power relay in the
vibrator supply
Pin 3   12 vdc to filaments
Pin 4   B+

The RCA AVA-126 vibrator supply had a resistor voltage divider which could
be tapped for 67, 165 or 250 vdc output.  I'd guess that the 67 vdc value
would be best.  The paper caps appear rated as low as 200 wvdc (assuming
they are still good).

73,
Mike / KK5F