[ARC5] BC-230 on 40 and 30 Meters: Now Good to Go

[David Stinson]

Using Ben's 9-pin sockets, one of Bry's 10.108 crystals
(and one for 5055 KC), 5763s and four other parts
 my BC-230s are clean and making contacts with
a mighty 4-Watts out on 30 Meters
and with the 6AQ5s and various crystals,
8-Watts out on 40 Meters crystal-controlled.
Here's how the 30 Meter rig sounds now:
http://home.netcom.com/~arc5/SCR-183/BC230on30.mp3
(I didn't mess with the 80 meter rig because when run as
designed, it's plenty stable.)

As you know, my "rules of the road" are no changes that
aren't 100% reversable.  Assuming all the prelim work to
get the set functional has been done (Hi-Z grounds,
recaps etc.)  we just change the Oscillator plate
circuit from series-fed to shunt-fed and insert the
crystal into the feedback loop.  It's quite easy.
Check out this photo:
http://home.netcom.com/~arc5/SCR-183/BC230toXtal.jpg

Between the Osc and the first modulator tube are the
connections for a dual oil-filled bypass cap.  The connection
nearest the coil mount is the bypass for the B+ feed to the Osc.
So this is the "B+ Point."  There are two wires connected here-
one running to the Osc B+ dropping resistor in the front of the
transmitter and the other running to the coil mount.
Remove the wire that goes towards the coil mount and solder
it to the crystal socket.  Connect a wire from the other end
of the crystal socket to the B+ point.  Don't worry- we're
going to "shunt" the current away from the crystal.

Connect an RFC (1mH or better) in series with a 100 Ohm
resistor and connect it between the B+ point and pin 2
(Plate) of the Osc. tube.  That's all it takes to put the rig
on Xtal control.  Series lamp is not needed if the rig is
run with as-designed voltages (mine runs on the dynamotor).

If using the 6-7.7 MC coil set for 40 meters, set the freq.
dial to around 1520.  Crystal should oscillate in that area.
Strangely enough, this freq dial acts like a VXO in my 40
meter rig, giving me about 5KC of "swing" before the crystal
becomes "hinky" and chirpy on each end.  Find the peak
output and detune about 10% off the peak on whichever
side gives better keying.

On 30 meters, the xtal oscillates with the Freq dial
at about 500.  It doesn't swing nearly as much as the 40 xtal.
Since I'm doubling in the final, I don't know why that is.
For 30 meters, I used a 5 MC coil:
http://home.netcom.com/~arc5/SCR-183/BC230-5MCcoil.jpg

The Osc coil is unchanged and runs at 5MC.
The leaf springs that held the Ant.tap broke on the PA/Ant. coil.
 Unless you have some way to work exotic spring metal,
that pretty-much finishes a coil.
So I re-wound it to resonate at 10 MC and it works great.
Good use for what was a useless coil.
I will write details about that if anyone actually cares.

One strange thing:  All crystals in this rig oscillate at
1 to several KCs lower than they do in a typical ECO ham rig.
For instance- the 10.108 KC crystal works at 10.107
and the 7.117 KC crystal swings from 7107-7115 KC.
Anyone have any ideas?

Also- since the original feedback is still in place,
if you de-tune the Freq control enough the set will
oscillate variable MOPA, but with much reduced output.
Stay with the Xtal oscillation area.

I'm really becoming a fan of this neglected rig.
My ARC-5 sets are threatening to divorce me for adultery.

73 OM DE Dave AB5S