I just purchased a 455 Command receiver on EBay. It appears to be untouched and included the Dynamotor. Reading something on a command page gives me pause. My intention was to get it working for my use. Everything I do to one is reversible, ie: mounting controls on the front is a plug unplug mod and the filament mod from 24 to 12 volt is reversible, no drilling needed anywhere on the set. The web page says there are so few untouched sets left that they should be preserved. So, that is a dilemma. Should I preserve it or use it? If I am to preserve it as original, what for? Perhaps I should find another set and pass this on, but to who?

Thanks for your opinion.

Ed

Good Morning Ed, I to have a few new Command sets. I am working on an R-19 (118 - 148 MC ) receiver project now. I was able to find information that is allowing me to run the radio as it was meant to be used with remote gain and speaker connections. If you can find a set of rear connectors, you can use the radio as designed. Without hacking up the radio.

Since its a 6-9.1 MHz radio, and has the dynamotor, why not just get a 28V switcher supply and use it? No mods necessary. You probably need a manual for the unit, and there are several available on the net, including the three old CQ Mag "surplus manuals".

Hi Ed,

I haven't done this with a rx but have with the command series tx. The rear socket gives you access to all of the connections you need the control the rx. The problem is where do you find a plug? Well I made one out of a few of the larger molex pins, red solo cup, and a bit of bondo. May have to expand the pins a little to get a tight fit in the socket. I'm pretty sure you can feed the the HV and heater voltage thru the back plug too. You could just pop the dynamotor off and power it w/an ac power supply. GL

Terry N3GTE

Yes, all the connections needed are available at the rear connector. A mostly compatible plug and pins can be found under each IF transformer in a junker set. (see pic)

I restored a pair of these, one with capacitor replacements (chicklet-sized capacitors, leaving the originals in place). The other was completely unmodified since it worked fine at the full B+ voltage.

I powered them by temporarily pulling the dynamotor and using a 24 volt transformer for both filament and B+ by way of a voltage quadrupler. Connections were to the three dynamotor contacts (ground, 24 V and B+) The simple quadrupler uses four 1N4007 diodes and four recycled 200 volt electrolytics from a couple of junk computer power supplies, 330 uF each but not critical, see schematic. The RF gain control can be much less than 50K. A 5K or 10K will work fine. The simple BFO switch just shorts out the BFO when not in use.

My articles on the restorations and powering of the Command receivers were in the January and February 2021 issues of The Spectrum Monitor

A lot of great information. Thanks to all of you. I need to take some time to absorb it and decide how to proceed. These little radios are interesting. I have three, I think and a couple of power supplies. I have a 25 volt transformer in my stash and I may build another one for 24 volt filaments instead of 12 like the ones I have. That way, this one would require no modification.

I have never heard one run on the dynamotor, so that is on the list of things to try. Seems like they would be pretty noisy, we will see.

Ed

Those dynamotors are pretty quiet. By now you should re-lube one. I use Polyrex Grease which is what the aviation industry currently uses on rotary converters and so on.

Bear in mind that the flower pot capacitors along the chassis aprons are probably all leaky by now. Cutting them open and re-stuffing is a lot of work but there are other methods.

An un-hacked one is getting rare. I cheated and just got some beat-up $ 5 ones at hamfests and they already had the controls and jacks on them from some previous owner. Then I didn't need to feel bad about the holes or how I refurbished the paper capacitors.

I have been pretty lucky with the capacitors so far. Most of the caps test like new. I have a parts set with mostly like new capacitors. I was able to swap out leaky ones in the sets I am using, so they all look original. I don’t care how old a capacitor is, if it does not leak, I keep it in these military sets. No regrets.

I had not thought about lube on the dynamotor. It’s probably like glue at this point in time. I will lube it first thing.

Ed

Reminder to those that work on these sets: invest in a set of spline wrenches, as most of the knobs do not have standard allen setescrews.

I have the 3-5mhz sets 2 of them got both working by recapping them and i use 12 volt lawnmower battery to run the dynamotor .They are quiet when running i did relube the dynamotor !I use a LS-3 speaker and single unit rack ,i did put a fuse inline! Sounds pretty good for what it is .They are as built other than the recapping.Angelo

Ordered the capacitors for the power supply mentioned above. I have used voltages near 200 in the past, so hopefully this lower voltage supply won’t matter. TubeR, I am figuring that bleeder resistor at 10K to 12K, is that what you are using? I am starting to work on a plug for the rear socket as suggested above. Tried some brass tubing left over from a WD11 tube project, but even the smaller is too large, so looking through my stuff for suitable pins. Thanks for the ideas.

Picture really has nothing to do with the subject. It’s just to keep the thread from being too boring for followers. My latest restoration by repairing then nickel plating components of the Lionel Key.

Ed

Unless you put it in a shielded box, what about RF interference?

John

Toober on eBay has NOS ARC-5 connectors from time to time. A good guy to deal with, too.

Hi Ed

You used to be able to get pins to insert into the back of the SCR-274N transmitters and receivers on ebay; a fellow sold them in lots of 10 or 12.

I just checked and didn't see them, but I think seller was kb4dmf -- just search for SCR-274N or ARC-5 and you'll see his connectors for sale; I suggest you email him and ask if still has any left.

They are gold plated, easy to solder to, and fit snugly into the rear connectors. I built up a few wiring harnesses with them and they were well worth the price (to me....)

Dynamotors -- I occasionally run my system with dynamotors for TX and RX. I find the dynamotor hum to be annoying for actual on the air contacts so I just use a base plate and feed in 28V and 190V from an old HP-23 power supply. If you decided to use your dynamotor, I recommend ground straps between the dynamotor and receiver base; that definitely helps cut the hum down.

Thanks for all of the good information. My parts set does not use the plug in type IF transformer, so I was out of luck on those plugs. I was able to find some things in my junk box that would work for both the upper and lower rear socket/plug. Attached is a photo of one. Parts for this one came from an octal tube socket. Those pins have to be exactly in the right spot!! I found a clear bottle cap the correct size which allowed me to see through and mark the exact spots for drilling. I have a habit of using what I have or can scrounge, but ideas came from above. I used a casting epoxy that I have previously used for making knobs

Ed

My B+ and Filament hook up for my R-19 receiver project. Three small binding posts, a piece of G-10 epoxy board, and a small aluminum box to hold the strain relief for the power cable.

All of the pieces of my latest round of ARC-5 gear were pretty sad when I got them. I wanted "JUNKERS", the best ones I could find for cheap or course, simply because I didn't want to invest much money in the project, so thoughts of preservation weren't part of the project, just wanted to get them on the air. Some took quite a bit of time getting them somewhat back to stock. The 160 meter transmitter was HIGHLY modified probably 50-60 years ago, but the workmanship was very good and it performed well as received, so I used it as is.

N2LXM, . I have to laugh at mine after seeing how professional yours looks, but the epoxy and shrink tube does a good job at strain relief. I do wonder how you managed to get those three pins lined up perfectly?? I am not that good at measurements.

The set arrived yesterday. I am not so lucky on this one as I have been in the past. Every paper type capacitor checks bad. All leak electrically and several are leaking green slime. Fortunately I have good originals on all but two and I can re-stuff those. Attached is a photo of three capacitor cans in this set. The one on the left is a replacement. The one in the middle has been re-stuffed and the one on the right is next for replacement. I think the re-stuffed one passes the grade as original looking.

It will take considerable time to get this one playing as well as maintaining originality, but it will happen.

Ed

The plate was easy to make. I first used a piece of cardboard. Pushed in down onto the pins and flex mounts. Then transferred the indentations to the G10 and drilled as needed. A coat of gray primer was then put sprayed on.

Mike, I like those “Junkers�, especially the Collins TCS 12!! LXM, thanks for the info. I can use it next time.

Used an old power supply just for the fun of it and the receiver works!! Now to button it up and build a power supply for it when the parts arrive. It’s going to appear totally original since no one can see inside the cap cans. It is not taking as long as I expected.

Ed