Need help with a Western Electric, pre-Command set Rxvr

[signalcorpsoperator]

Hi there fellows---
I have a friend here that recently made out lucky at a hamfest, came home with a BC-AR-429 radio receiver. From what I could tell by a fast look, the radio is in mostly unaltered shape, there are a couple of alien front panel holes, but for the most part, electronically it is unscathed. There is a large power, remote control ?? jack on the front panel, with several pins, about the size of a banana jack in diameter and length. I believe that there were about 7 ?? or so of these pins, inside a large metal ring that composes this monster plug. The plug itself would be about 2 inches or so across.

This radio has a plug in coil unit that is to the best of my knowledge intact, and it is a pre-Command Set ( got it there Curt ), design. From what he knows, this radio design dates from about the early 1930's or so, which seems about right. I know that it used some kind of remote control tuning setup, for setting the radio away from the pilot, yet still being able to be used.

The information that I am trying to find is a manual, schematic, or even a pin out of this weird plug, so that he might be able to build a power supply in order to test it with. I would greatly appreciate any and all help with it, thanks guys !

Regards---
Tom
_________________
Civil Defense + CD Exercises = a population that is prepared!

[AAFRadio]

It's part of the SCR-283, Tom. And it's okay to call it a command set - several flight operating manuals of the period call it that very thing. I have a manual I can scan the schematic from, but won't be able to do it until this afternoon. The connector provides 28vdc filament and B+ for the receiver, along with audio and lines for the remote control. It normally uses a dynamotor that provides B+ for both the receiver and its companion BC-**-430 transmitter, through a junction box that distributes power and control lines. It is similar to but not identical to the Navy RU series receiver.
_________________
- Mike KC4TOS
http://aafradio.org

[Curt Reed]

No problem calling it a Command Set, for sure! After all, it was the original Command Set for the Army Air Corps. While the Navy had their RU sets, the Army bumbled along with the SCR-283 sets.

They were mainly used in flight trainers like the PT series of aircraft. I have only seen one complete set in my life, and it was in a Vultee Vibrator and the transmitter was mounted low on the firewall to the right of the rudder bar and the receiver was behind the pilot. I do not know if that was the standard way to mount them or not, as there is so little information available for them. today.

When I was a kid I had a cardboard box that someone gave me and it had the junction box and about a dozen of the large pin connectors in it. Today, the lack of those junction boxes and the connectors is what dooms a lot of these sets to not being assembled like I did with my SCR-274N set. How I wish at times that I would have kept that box of goodies!

Fair Radio Sales were selling the complete receivers for $7.95 new in the boxes back in 1963. I was about to order one, as I was studying for my novice ticket, but was advised against it, as the receivers are TRF designs and very poor on selectivity.

Also in that box of goodies was a dog eared manual for the sets. Over the years it got more and more dog eared so it was finally discarded also.

However, there is one thing to keep in mind. There were both 12 volt versions and 24 volt versions made. I may have a couple numbers crossed, but I think it was the SCR-183 that was 12 volts and the SCR-283 was the 24 volt model.

The BC-AR-429 and BC-AS-430 transmitters were of the 24 volt type and the BC-AR-229 and BC-AS-230 were the 12 volt versions.

At the time they were used, mainly in the early 1930's most trainer aircraft had 12 volt electrical systems if they even had an electrical system in them. I think 24 volt systems for trainers did not come out until sometime around 1935 or maybe even later.

Also the primary developer of these sets was Western Electric. I do not know of any subsequent manufacturers of them other than W.E.
Curt
_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!

[signalcorpsoperator]

Hi there guys---
Wow, thanks so much for the information ! Good deal on being able to call them actual Command Sets, neat radios.....

I think that intact ones, modified or not, are getting to be pretty scarce these days, as I have only seen one or two at a past hamfest here, high prices on them predictably. I would really appreciate a copy of the schematic for this little set, thanks Mike ! Could someone use 24V on the filaments, instead of the original 28 ? I don't think any damage would be done, just that 24V is easier to come by for a newbie to the hobby. Thanks again gents, I appreciate the help !

Regards---
Tom

[Curt Reed]

No problem with the voltage. Just like an automobile, the voltage when the engine is not running sits at about 12 volts, but with the alternator charging, it runs 13.8 to a bit over 14 volts. And older cars with six volt systems mainly ran about 7.2 volts when the generator was charging.
Curt
_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!

[AAFRadio]

Tom, I've just emerged from an hour in the chaos of the radio shack after we moved down here, but with only an SCR-183 manual. Not a problem, really - all the later models share the same circuitry except for filament strings. My good friends Dave AB5S and Michael WH7HG have been researching the RU/GF and SCR-183/283 series from its inception around 1932, and interestingly enough both are Aircraft Radio Corporation designs based on the ARC Model B, responding to different Army and Navy contract requirements documents. It is unclear when Western Electric muscled in on the program, but that 900 pound gorilla had a habit of doing that when large quantities were needed.

I am going to have difficulty in scanning the schematic for you this weekend because of other commitments, but to help get you started, here are the pinouts on the connector from the manual:
45 - aircraft battery
56 - 216vdc (derived in the dynamotor base from pin 57 through a dropping resistor and filter)
57 - 260vdc
55 - audio output
53 - ground
46 - manual sensitivity control to arm of 40k ohm variable resistor with 200 ohm R between lower end and ground to prevent bottoming currents
54 - need to ground this pin in order to to enable manual sensitivity control

[signalcorpsoperator]

Hi there Mike !

Thank you so much for the pin out, I really appreciate all you effort here to help me out. That is interesting the way those sets worked, guess that as is typical with military stuff, they will forgive you if you don't give them a lot to work with ! I will get in touch with the owner of this radio, and see what he has to say about it. Might have to make a pack out of a ton of 9 volt batteries for initial testing, but that should work fine for starters, would definitely give an idea if the set is in any degree of working condition.

Thank you again sincerely for the help, no hurry on the schematic, PM me when you have the time.

Have a good one---
Tom
_________________
Civil Defense + CD Exercises = a population that is prepared!

[AAFRadio]

Oh my goodness, if you want to pursue this kind of work for long, you need to build or acquire a variable B+ supply. Nine volt batteries won't cut it for long, and you can't bring them up slowly to reform capacitors. I don't know what I'd do with my old pair of GR 1205B's...

The dropping resistor between the B+ and pin 56 is a 5K 10 watt power resistor, bypassed by a capacitor in the receiver. The RU series receivers eventually moved the dropping resistors to the exterior of the junction box to keep the dynamotor base much cooler. Motors don't like heat, and it was a bad idea to put them there in the first place.

You'll enjoy the -429 once you get it running...it is a classic end-of-life TRF receiver that is beautifully executed, though like all TRF Rx, it is pretty wide on crowded bands. A preselector with decent Q and near-unity gain is a big help, despite the number of stages in the basic receiver. The absence of heterodyne whistles as you tune through the bands is a relief, though. The difficulty is in finding a minimal set of peripherals, like the tuning knob. The system used for tuning uses the larger Bendix spline (as opposed to the smaller diameter ARC design used on the ARA, 274N, and ARC-5 sets.) Luckily those are much more common and less expensive than the ARC pieces.
_________________
- Mike KC4TOS
http://aafradio.org

[signalcorpsoperator]

Hi there Mike---
LOL, OK, sounds like I will have to keep an eye out for one at the next hamfest, would definitely make things easier ! I sent an email to the guy with the 429, have yet to hear anything as yet though. Thanks for the info update, it looks like he will end up making a cable assembly for that thing..... Doesn't look like it would take too much work to get the radio up and running, not a very complex set I would suspect. Since it is a TRF radio, probably not going to be as sensitive as a superhet from the same era, but neat just the same !!! Thanks again !

Tom
_________________
Civil Defense + CD Exercises = a population that is prepared!

[Curt Reed]

I would not say the receivers were not sensitive as compared to a superhet. Actually some people may think just the opposite, that they were more sensitive, but it depends on how you look at it. The selectivity was as broad as a barn door, so every signal within 20kc came thru and all the signals plus the one you are trying to listen to adds up to a lot of noise, which can fool people into thinking they are more sensitive.

An interesting topic of 24 versus 28 volts in aircraft can be said for the BC-375E liason transmitter also. It had a rather complex resistor network to set the filament voltages on the tubes to the correct value and after the proper taps were selected, the change from 24 to 28 volt operation was with a toggle switch in the tube compartment. The manual says 24 volt operation is when the aircraft engines are not running or the generators not turned on. With the engines running and the generators turned on, the supply voltage would be 28 volts, so the switch was provided for both voltage settings.
Curt
_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!

[TomS]

Mike - If you're scanning the manual, I sure would appreciate a softcopy of it. I have the same receivers and the same problems in finding information. TIA - Tom

[Burnt Fingers]

End of life design? Maybe for the Army but the Navy had the RAL HF radio in service well into the 60's as a backup on auxiliary ships such as tankers. Im constantly amazed how well that TRF plays here even on a most simple antenna. Aboard the tanker I was on it used a 200' long wire about 90' above the water. Crank in the regeneration and internal audio filters and the selectivity becomes quite acceptable for CW.

Carl

[Curt Reed]

Yes, the RAK/RAL sets were good performers that's for sure. They had to be to be in service for such a long period of time. However comparing a BC-AR-429 to a RAL is like comparing a Hallicrafters S-38 to a Collins R-390A.
Curt
_________________
Curt, N7AH
(Connoisseur of the cold 807) CW forever!

[signalcorpsoperator]

My point exactly ! They are good radios, but they have limitations. If working though, they present a seldom seen side to radio history in today's world ! I have yet to hear from the guy, but we'll see what he has to say about this information. I have no idea if he has any experience building power supplies, hope that he does, he'll need it. Thanks again guys !

Tom
_________________
Civil Defense + CD Exercises = a population that is prepared!

[Tim Tress]

Fair Radio Sales is still in business, and they just might have something for that set.

http://www.fairradio.com/
_________________
Tim KA3JRT