In article ,
Bill Bird wrote:

(trying to get this posted correctly, quite rusty)

Hi,

I've just gotten my Central Electronics 20-A working nicely on cw into a dummy
load on 3595 KHz using my one crystal. I've got a VFO 457 and VFO 458 that I'm
wanting to begin using for my first time. I'm starting with the 457 and could
use some help.

Instead of a 0C3 tube the unit has a 0D3.
Instead of a 1626 tube the unit has a VT135/12J5GT tube.
The second 1629 tube has not been removed (no wire to top cap)


The "Basic Modification of the BC-457, BC-458 or BC-459 as a VFO for Model 10 or

20 Multiphase Exciter for 12 Volt Operations" states at one point: "Remove the
1629 eye tube and also the 1625 located near the tuning shaft, Jumpers should be

installed across the filament terminals of these unused sockets."

I'm guessing having the second 1625 installed without a wire to the top cap
might be just to provide the jumper across the filament terminal for its socket.

I don't know where the 1629 eye tube used to be. I also wonder why the 0D3
and VT135/12J5GT are installed.

From memory, the 1629 (magic eye) tube was at back left, an octal base crystal
was fitted to the middle socket (the pair of these provided crystal calibration
at 4.6MHz (on the 4 - 5.3 MHz unit), and the 1626 oscillator triode was in the
right hand socket. If it still has the top case, the hinged flap has a mirror
fitted over the 1629 position so that you can see the eye from the front of
the unit.

The 0D3 is just a regulator to stabilise the oscillator HT.

Chris.

--
"George Flynn told us at Ditto that he knew he'd been in fandom too
long when he went to see THE SHINING and found himself evaluating the
hotel's function space." --Richard Brandt