(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.

I am thinking this VFO 457 was modified and working many years ago. This VFO
457 was hooked up to the 20-A when I got both units. Thanks for your help on
the VFO 457 or any comments about the 457 vs the 458 since I will be trying to
get both working but focused on the 457 for now.

73,

Bill Bird
KG0YJ
Chesterfield, MO

Q. Instead of a 0C3 tube the unit has a 0D3.

A. Just a different regulated voltage. No magic about voltage. In fact,
the builder may have found that the different voltage may have offered
better stability - or it could have been he had one on hand.

Q. Instead of a 1626 tube the unit has a VT135/12J5GT tube.

A. Should be an equivalent tube. No big deal. A triode is a triode.

Q. The second 1629 tube has not been removed (no wire to top cap)

A. You apparently mean the 1625 power output tube. Should not make much
difference. Maybe the builder did not have a place to put it. The original
BC-457 had tubes in filaments in series - parallel so it could operate on
the aircraft 24 - 28 volts. Most hams converted the wiring to 12 volts by
paralleling everything. I recall most conversions supplied a separate
filament transformer, and as long as the voltage required is equal to the
transfromer voltage, you are fine.

Hint, if it worked once, and no one rewired it, it will still work - unless
one of the components has died due to aging.

All the BC-457 conversion does is to use the triode oscillator circuit as an
external vfo. Output from the vfo is taken from the grid circuit in the
BC-457. It is a very easy circuit to understand.

For 80 and 20 meters, you use 5 to 5.5 MHz. For some of the other bands,
you must multiply the frequency of the vfo. That was often done in the 1625
section. But, much of the operation of the CE was done on 80 and 20 and the
fellow who installed it may not have gotten any further.

Colin K7FM

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

Thanks for the help Colin and Chris. The BC-457 is working fine. I'll put the
BC-458 on the shelf for now.

Bill Bird
KG0YJ
Chesterfield, MO
kg0yj at arrl dot net
www.billbird.com

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.

I am thinking this VFO 457 was modified and working many years ago.
This VFO 457 was hooked up to the 20-A when I got both units. Thanks
for your help on the VFO 457 or any comments about the 457 vs the 458
since I will be trying to get both working but focused on the 457 for now.

73,

Bill Bird
KG0YJ
Chesterfield, MO