The AM Forum

I just bought from eBay a new in the original box, untouched ARC-5.  It has a date of June 1943 on it.  Frequency range is 5.3 - 7.0 MHz.  This radio is 74 years old and no ham has had their paws on it to modify it.  Everything is original.

I'll post pictures of it once it arrives.  I want to carefully take the covers off to look at the innards (in color, in person and not from a 1940's black-and-white photo). 

I was thinking about making some minor modifications; just enough to put it on the air.  But then I thought, nah, what's the point?  It's a little 10 watt transmitter.  Most everything nowadays can run circles around it.  Once I start clipping, it's no different than all the rest of the junk ARC-5's out there.  I'm going to put it back in the box and store it in my closet for as long as I'm able.  The historical value is worth more than a few QSO's with it.

Jon

  Wow, its like the unbuilt kits I see people run into.  But you can't have your cake and eat it to so your right once
you start snipping, virginity lost!  await pics!

So I have to ask, how much did it sell for?

$127 plus $35 shipping.

Jon

Box sealed or open? Yeah Jon, I'd leave it original. Even though it's not in the ham bands, it's still a fairly rare piece of history. Get a beater to fix up and play with

It would be pretty easy to modify the frequency range, but I am keeping it all original.

The box is open, but it looks like he opened it for eBay picture purposes. I'll see for sure when I get it.

These were sold for next to nothing after the war. One of my coworkers was telling me he bought one in 1974 for $3. You see these at hamfests and they're always in junk condition.

The radio is 74 years old and I should be able to easily carry it to its 100 year mark.

Jon

The necessary original things to make it functional are still available:  Mount, dynamotor, tuning knob or remote control.

Ferret out those items and you'll have a neat RX without any mods.

73DG

Yeah, after this last building spurt, I was told that I need to return to the family. I guess time flies when you're having fun. Also, I need to cool it on buying stuff.

Jon

I misread your post and thought you had a receiver. 

Change that list to a modulator, mic, and antenna matching/ammeter.

That would really make the setup super collectable.

Take your time and buy easy.

73DG

Jon,
       Save the nice one for the collectable it is. I've got a couple that are in nice used shape and other than doing a super detail job on them, I'm going to leave them as-is.


Some ARC 5 tx's and a couple GF series tx's.

How times have changed.  In my early years of high school in the early 60's, I bought that 40 meter version of an ARC-5, brand new and sealed in it's box, for $5.00.  I also bought one that covered from 800 kHz to 1300 kHz For $5.00.  That one was rare, because a lot of kids bought that one to use as a bootleg AM broadcast band transmitter.

73
Ted
W8IXY

Probably in some abandon warehouse in the south Pacific there are tons of arc 5s sitting in boxes.  I think I still have some of the shock mount bases for those radios.

Fred

I also got one of those 5.3-7 MHz jobs in black crackle new in the box at Fair Radio back in the early 1980's. Nobody bought it because it had a rattle. It turned out to be one of those little plastic insulator balls had popped out of the tuning variable. I have seen those missing in other hamfest ARC-5 transmitters and sometimes it happens in receivers too. I paid 19.95 of course! That is 50 bucks in 2017 dollars.

I just got it in its original box.  Here's some pictures with the top removed.  All screws still had the ring washers. 

Unfortunately I can't take the bottom off.  The heads broke off of the two screws on the corner underneath the oscillator tube.  I tried to ease them out, but they still broke and the screw itself is preventing me from sliding the cover off.  Maybe the person installed it at the factory too tight, or 74 years of storage seized them. 

Jon

But, I'm not going to do anything to it.  It's now sitting prominently on a shelf in the shack.

Jon

Very nice. Takes me right back. Still have a lot of forgotten components in the junk box. Your pictures reminded me where they originally were placed.

When xmission op. standards are relaxed on 60 meters, fire that baby up as is !  ;D

It's a shame the old girl will never do what it was built for. But...... that's just me!

Interesting to note in the first picture is a piece of string that is cinched in the front panel. It came from the factory that way. Maybe the assembler left it in by accident, or maybe she left in a little good luck charm for the boys. Anyway, it's fun to speculate.

I contacted the seller to see if he knew the history of the radio. He said that it was owned by a ham in NJ. He owned lots of ARC-5's and had many on the air. When he died, the widow gave it to a guy who worked at Bell Labs in NJ. When that guy retired and "moved south," he asked the guy I bought it from to sell it for him along with a bunch of other gear. So, lots of OM's in this story.

To put this on the air the right way, you do need to update some caps and move some variables around. To do that, I'd need to break the paint on the screws. I just can't bring myself to do it.

Maybe when it hits it's 100 year mark I can light the filaments. To do so, I'll have to have Marconi exhumed and use a piece of his hair and clothing in the ceremony.

Jon

My father in law was a radio man /rear gunner on a PBY in the pacific during WW2...He reconized some ARC-5 radio gear in my shack..When I asked him how those radios were when they were new, he said "About the time the station comes into view, you can work them."

Yeah, a very short antenna strung from behind the cockpit to the rudder add to that about 20w out, I could imagine the performance.

Jon, to do the required surgery to fire it up into a DL wouldn't hurt. It may possibly run without exercising the internal adjustments (which would require breaking factory paint seals), and the only thing left is to address the 3x.05 cap can in the rear. A plug can be made for the rear with a piece of G-10 and if IIRC some #10 solid copper wire. Dealing with the broken bottom screws would be the biggest thing, very careful surgery that would require a slow and steady hand with a drill press.

You know you want to see it work. ;D ;D

   

Few drops of ATF onto the screws before you try to take them out will usually help.  ATF is better than any 'threadbuster' made.  If needed, use acetone to thin it to get it to seep into threads.  I don't like the acetone though:  Seems it will take paint up, too.

Otherwise, a very short bit (to protect from wander of the drill bit point) will allow you to drill the old ones out.  Then you can either tap a new thread, or insert PEM nuts and move forward.

--Shane
KD6VXI

It's like opening Pandora's box.  True, I may not have to exercise the VFO variable adjustment cap (I would though if I wanted to cover a good portion of 40 meters).  After that, the only "necessary" replacement would be that 3-cap assembly in the rear.  But once I started, it would be hard to stop incremental modifications.  

As for the two screws with the broken head, I'm going to try to use a smaller left hand bit to remove them.  I'll give it a quick shot of WD-40 and let that set for a while.  Then, I'll use the #47 drill bit to try to extract the remnant of the screws.  

Replacing those two screws will be the only modification I do to this.  Besides, a 10-watt chirpy signal?  After playing around with QRP for a while, I've come to the firm conclusion that it absolutely sucks.  Sucks to the max...  gag me with a spoon.

https://www.youtube.com/watch?v=AhBTtM6rexw (https://www.youtube.com/watch?v=AhBTtM6rexw)
(the reference for people who weren't around in the 80's)

Jon

NO! Don't do it! I thought about LH drill bit for about 5 seconds the other nite. It works FB for large fasteners, but if the bit got snagged and it broke, well, tool steel is a b#tch to cut out! That small of a bit is sure to snap.  :o :o   I'd use a center drill or a mechanics length bit like Shane said, the correct dia. and using a drill press, carefullly center and take light bites till the remnant of the screws will pass the holes to take the bottom off. You can then get the remnants out with other means without the worries of wrecking the paint on the chassis, or heck. just flush them up a little and don't worry with those screws; they're on the rear anyway. 

Have you ever had the chance to read WU2D's ER articles on the tx? Mike has spent a lot of time with the ARC-5 stuff and has the dope on them up front. We can all play around and figure them out, but all the info is there already. Get a copy fo the articles, I think 3 or 4 total, and read them; very informative, especially the mods for the out of band units.

Hey, you paid the money for it and we all know you wont butcher it up, so do what makes YOU happy. I'm not happy with non functioning shelf queens either. I'm slowly working on an ARC-5 setup for 75m phone. Have all the stuff on hand finally, now the hard part, putting it all together. 

Tranny fluid werks ok....  An enjiner I knew use to swear by Diesel.


KLC

You know, that's a good idea.  I used a drill press to carefully eliminate the screw head that was sticking out, enough to get the bottom plate off.  I'll then just file off the remaining screw material.  I'm not interested in machining out the rest of the screw to make it perfect.  I'm not that good enough of a machinist to do it right anyway.  But yeah, doing this much definitely required a drill press.  Doing it by hand certainly wasn't going to cut it. 

But, I did get the bottom plate off.  I've attached a photo.  All original stuff, as you'd expect. 

I guess what makes me happy is having a shelf piece.  My wife asked me if I was going to build a power supply for it and put it on the air.  I said no, and she agreed and said that I'd never get another one of these pieces again.

Jon

Does it have that "smell"?

I don't really know... I didn't put my nose down there.  Sometimes it's best not to.  One surprise though was opening the rear cover on top.  My wife said, "Oh, a mirror!"  And I'm like, that's for calibrating the VFO with the seeing-eye tube, not for putting on makeup. 

Jon

It's a work of art. I bet many of you think so too even if you have a four module class E rig sitting in the background. I've never been able to explain to someone not similarly enchanted why pieces like these or other cleverly designed and carefully constructed pieces are things of beauty.

Your right, sometimes it's best not to put your nose down there, but it's just radio equipment in this instance, so it's O.K.

I don't know what it is about old Military electronic gear, but it has that smell. I've learned it over the years, and it is unmistakable. Don't know what it is; varnish, MFP, or maybe some toxic substance, but it does signify that said equipment is of major coolness. And no, it's not the smell of damp basement, mouse pee saturated Hallicrafters S-40. Consumer electronics of the same period does not have "the smell", although they do have a certain scent especially when the toobs are lit.

Who knows? I doubt if any modern US mil. equipment has "the smell", since most of it, or the majority of it's parts, is made in Asia. And we know what Asian electronics smells like, right? Plastic.    

    All my ARC-5 stuff has that smell, or variations on it. By the way I rencently powered up an unmodified 5.3-7 MC Navy unit and at 650 on the PA and 300 on the oscillator with a 22K PA screen resistor got a paltry 35 watts out. The bypassing is not so good either- Touching the power cable coming out of it actually pulled the vfo. So much for running un-modified.

     I have two complete ARC-5 transmitter setups here: one fixed, one mobile. Both easily put out a 100 watt carrier. They are plate modulated."Navy" ARC-5's are using a shunt fed tank circuit and were designed to be plate modulated. The mobile rig uses a modulator built on an ARC-5 transmitter chassis. It uses a pair of 6883's (12 volt 6146) with the grids grounded and the screens driven by a Valiant driver transformer and 6V6. Mobile power is form  GE Mastr-Pro mobile power supply strip. The mod transformer in both rigs is an ART-13 unit. The base uses a pair of 807's resistance coupled in AB-1. Both use inverse feedback around the entire chain and are full on HI-FI audio. It's power supply/modulator is built in an old Wasco AM marine radio cabinet.

  To get 100 watts out of an ARC-5 I update the bypassing on all the tube cathodes, screens etc with ceramic caps, using the shortest leads possible soldered to the tuning cap frames. I shunt the PA plate choke with a National 2.5 MHY choke to cure a voltage drop issue, and add a bypass cap at the bottom. Note that you MUST replace the plate blocking cap with a good ceramic of 500 pF to .001 at 1.2 KV or higher. The stock cap will EXPLODE otherwise (It happened to me more than once). Get rid of the fuse link between the top of the plate choke and tank coil. Next I resonate the coupling link with a large Arco mica trimmer cap of around 1200 PF in paralell with the link located as close as possible to the terminals on the link (this is important). Unlock the PA tune cap and juggle it along with the added trimmer and the coupling control to get to max RF out. With 700-725 on the PA plate 300-325 on the screens and 300 on the oscillator. Use a 22k screen resistor (per the RCA tube manual)and if all is right and you have good tubes you get to 100 watts. The tubes show no color and I have had no issues running them like this. 

     The pictures are of this setup in my 78 Chevy Caprice. Power is from a GE Mastr-Pro power supply strip. The system works flawlessly even on old buzzard transmissions. I stopped using the Icom 718 as a receiver in favor of a Drake SPR-4. So nice to have a world class receiver with noise blanker in the car. The CB with converter it tried didn't cut it in the real world due to really bad image rejection on 75.