[MRCA] Looking for BC-AL-430 Transmittter Info and Related Items

[Jack Antonio]

Hi Chris

Just got back from Dayton (and Fair).

Yes, I have an SCR-183. I'll have to look at the
books, but I think the B+  is around 350 to 375.
Did you get the right tubes for it?  VT-25s are
not cheap, but can be had, but the VT-52s are
stratospheric in prices, when you can find them.

Dave Stinson did some work and found that triode
connected 6AQ5 can be substituted, but the problem
is that they are *too good*.  The problem is this.

All bias voltages in the transmitter are developed
from the grid of the PA stage, and the 6AQ5 oscillator
develops much more bias voltage than the original tube.
So, I had to shunt some resistance to lower the bias
voltages down to allow enough plate current to flow.

I'll dig up the details and let you know what I did.

I am trying to find the time to try some other tubes
like maybe some 6V6, 6Y6 or similar tubes.

You can test the transmitter outside the case, but the
tuning will be different.

Another problem is that the can type capacitors are
starting to show problems, like leakage (both electrical
and oil), and need to be bypassed, or rebuilt. This
applies to both the tx and rx.

The SCR-183(283) (BC-229(429))receiver does not have a BFO, so is
limited to voice and MCW, but the tx control box does
have a key jack, built in key, and mode switch for
Voice, CW and MCW.

You know, I didn't try mine on CW, next time I fire
it up, I'll check the note.

I don't know if the coil set can be padded down, I'm sure
the oscillator could be brought down with an added cap, but
not sure of the PA coil. Just would have to try it and see.

BC-229(429) receivers are not too scarce, and most of them will have
a dual coil set that covers 200 to 400 and 2500-4700. There is
a coil set that covers roughly 4500 to 7700, but they are somewhat
uncommon.

Connectors are available, try Steve Williams.

One myth that you will run into, is that you can use the Navy
RU and GF coils, as they will fit mechanically.  They will
*not* work in the Army set.  The transmitter circuit is
completely different, and the Navy coil sets have a BFO.

(Note that the very, very early sets might have had
interchangeable coils, but most sets you see today
do not have interchangeable coils).

Hope this helps, let me know if you need any more information.

Jack




On 5/14/2014 5:47 PM, Christopher Bowne wrote:
> Picked up an apparently un-hacked BC-AL-430 at Near-fest.  Missing
> tubes, but otherwise in good condition.  Looking for info on getting it
> on the air, figure I can run about 400 VDC  for B plus, I believe it
> uses 12V DC for filaments, even though it is designed for use in 28V DC
> aircraft.  Jack, WA7DIA, don't you run one of these?  Surprised that the
> original application was voice only, with no CW or MCW mode.  Can it be
> made run on CW without bad chirp?  I came with a 4 to 4.something
> megacycle TU, can it be pulled down into the 80/75 meter band with that
> TU?  I would definitely be interested in a TU that actually covers the
> 3.5 to 4 mc.
>
>
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