The AM Forum

    I bought this last year around this time. Got to get started on something and I believe I have enough parts to scratch up a P/S and whatever else it needs. I know it needs the vacuum relay (a regular open frame should suffice) and autotune lamp. I'm thinking of tearing it down and starting with just basic chassis needed to generate carrier; get that part right first, then proceed. Does all the subchassis just unplug or will I have to unsolder?

I have taken out all the toobs and meters and gave it a good bath. Looks better now, but still rather ugly.

Phil

A lot of times they work with out any changes. Tearing it down might be a lot of extra work for nothing.

You need a low impedance mike with fairly high output as the audio gain is marginal.

There are suitable CB mikes out there.

Or a carbon mike

NOS vacuum relays show up on ebay frequently, that is where I got my spare.  I use an amplified D104 which works great.

Rich

Electric Radio had two nice ARTicals a few years back.......

klc

PS, anyone have a auto tune hand crank???

I redid the audio amp for a D-104 per one of the conversion articles and opened up the bandwidth a bit. I didnt want it to sound like an ART-13 ::)

The main thing is to clean and relube the autotune so you dont fry the motor; it wasnt necessary 60 years ago when the conversion articles came out.

Carl
KM1H

In addition to Carl's clean/re-lube advice you also should perform the ER mod which removes voltage from the autotune motor when it is not tuning.  This will greatly reduce the heat generated in the now senior citizen motor.

Good point Roger, I didnt read ER when I did the work and havent been into it since  its rarely used these days unless 17M wakes up. Its on my to do list.

Another autotune warning......dont try and force anything even in manual....if its jammed/gummed up fix it.

Carl

   Thanks for the link Brian and to all the others who replied. The biggest problem now is to interpret all the J.S. haywire of the added "pigtail" someone added. They probably didn't have the Cannon plug for hookup, so they cut all the wires; even the ones going to the accessory connectors.

I have most of the upper cabinetry removed except for the part that contains the switches and meters. The audio amp and MCW/CFI units have been removed to simplifiy testing. Hopefully, my bonehead method of testing will be to first figure out the wiring, then get the tube fils glowing and check the voltages at the sockets. Then, get the osc. percolating, doubler section, then the final. Looks like the bandswitch timing needs to be adjusted, as well as a good cleaning of all the switch and relay contacts. Would the control L.V. ckt work o.k. at 24 VDC, or does it have to be exactly 28 V?

Phil

The motor is powered when it is not moving?

Rich

From what I gather to keep the motor pre-warmed at high altitudes. Probably the same reasoning for the vacuum relay used in ant. switching.

Phil

"Would the control L.V. ckt work o.k. at 24 VDC, or does it have to be exactly 28 V?"

I suspect the control circuit (relays and autotune) would work fine.

But the tube filaments use series dropping resistors so you would want to check the filament voltage -- particularly on the 811s and 813 to be sure they are within spec.

Rich,

I don't have the article handy right now but as I recall it is the field winding that is continuously powered whether or not the motor is running.  I made the modification in mine several years ago and it is very simple to do.  Cleaning and re-lubing the auto tune mechanism wasn't :)

Phil,

The unit looks about normal for an old ART13. Return the audio to original, lube, finish the contact cleaning, stick in a relay and fire her up!

Start with the 28VDC and see if everything lights up and the relays and autotune works.

Mike WU2D 

O.K guys, filaments lit and autotune motor runs, but I initially made a very stupid mistake. While I was trying to figure out the connectorless J.S. ratsnest of wires from a previous owner; I had temporarily unhooked the F2 field hot at the motor. After running everything down and building a temporary 28v supply; I lit the filaments. After about 15 seconds, I began to smell that magic smoke --- THE MOTOR! I quickly shut it down and let it set for 5 minutes, remade the F2 connection, and hesitantly ran the variac back up. The motor began to run, even set on MANUAL. I shut it back down quickly as soon as I heard it because I had the controls unlocked; so I locked them, ramped it back up again and let the motor run. It seemed O.K., so I tried several presets and let it run out. I hope I didn't hurt it too bad with that dumb move, probably a little rough on the brushes --- stinky!

Phil

Phil,
    That was the smell of all the crude that will bind the motor burning off.  The heat from what you did re-emulsified gummy oil in the motor so now it is properly lubricated.  The contact points of the brushes are now all "electrically" cleaned and ready for operation.

I live in my own special world, it is perfect here.

Rich

Ahhh yes... that's the ticket. I meant to do that; it's called electrical burnishing of the brushes to eliminate any buildup that had formed over the years of sitting unused.

I was looking into an ART 13 and was advised against buying coz they drift a lot.
So maybe there's a freq stability issue.

Fred

Your adviser must have wanted it for hiself ::)

They do drift while going from sea level to 20,000' in an unheated bomber.

Carl

I had an ART-13 when I was in high school.

A couple times I zero beat it with WWV at 10 MHz and then left it running all day in tune mode (final not running) and came back to check it eight hours later.

Still zero beated with no noticable drift.

It was more stable then most tube rigs of the 50's and 60's era.

Still zero

Plan on adding external loading caps to get the transmitter to load correctly into low Z coaxial loads. I used a 400 pf var along with switched blocks of 400 each for a max total of 1600 pf. On 75 meters feeding a matched 50 ohm antenna I use about 800-900 pf.

The external loading cap also helps with second harmonic reduction. I looked at the output of my ART-13 with my HP spectrum analyzer and without external cap or if using low values of of cap (200-300) the second harmonic might only be down 35 db. Using 800-900 pf on 75 the second harmonic was down >55 db. That's with 140 watts output and 1200 volts B+.

Good luck.
Steve,
WA2TTP

"
P.S. The old CAF, (Confederate Air Force) use to give rides in the bombers. I don’t know if the new CAF does or not. They probably do, but its not the same organization anymore.                "

Funny u said that ......  It's not the CAF, but,

http://www.libertyfoundation.org/index.html

klc

My uncle flew in B-17's out of England and they used headphones with foam rubber surrounds. You could even pick them up NIB surplus in Radio Row, NYC in the 50's which is exactly what I did. The noise in the plane couldnt have been too bad as he didnt have any hearing loss even into his 80's. He was a little guy and he gave me his flight jacket when I was about 12-13 and grew out of it a few years later; I still have it along with his cap and various other items.

I found a set of "cans" at a fleamarket years ago; seems like they were made by Superior? and had what seemed like a mil-spec # on them. The earpieces were bakelite, but the cans were chromed metal and they did have ear cushions on them made from leather and filled with cotton fiber. They were so badly deteriorated I had to scrap them (cushions). They were my first set of hi-Z phones and I still have them; they work F.B. but get to be annoying after 15 minutes wearing them.

Phil

I'm a little puzzled by the earphone comments, because properly configured WWII earphones actually perform quite well in a noisy aircraft.  They were never meant to be worn without cushions (or sockets, as they were technically called back then), and considerable effort was given to designing them at Bell Labs and Harvard.  The USAAF favored an all rubber Bell Labs design called the MX-41/AR, while the Navy used a different approach with a larger diameter and chamois pads for greater comfort, known as the Harvard Design 5, or NAF-48490-1.  Either one provided isolation comparable to today's sets, and in fact were the direct engineering predecessors of same.  The breakthrough was a series of Bell Labs studies that concluded that the ear needed to be totally enclosed by the socket.  I have more at http://aafradio.org/flightdeck/Peripherals-headsets.html for those so inclined.

"more at http://aafradio.org/flightdeck/Peripherals-headsets.html for those so inclined"

Nice site. First time I've heard about it.

Dave

One of my favorites. Mike has unwittingly contributed to my delinquency on more than one occasion.  ;D

Probably the most comfortable and good sounding earphones I ever used were a set of WWII surplus with the large rubber cushions that looked like a giant suction cup. One of the CW guys had them at Field Day years ago. Never had any luck finding a set, though I saw Fair was selling the cushions for $25 a while back. The other smaller, more solid rubber cushions look more like a toilet plunger and though the phones sound good, comfort goes away fairly fast. They press against the ear and don't seal.

Those chamois cushions are nice and seal around the ear well. I've got a couple sets of those with the pic attached ala 'Strategic Air Command' with Jimmy Stewart. They also work fine.

Phil, I wonder if the set you found were maybe cobbled together from pieces? I've seen some of the bakelite ear cup versions, some were used up through Viet Nam for training and such. Same basic design, canvas strap headset with the adjustable poles on the side, metal earphones clipped inside. I don't recall ever seeing the 'shiny' types with rubber or padded ear cushions.

Always happy to contribute to delinquency...at least of the radio variety.  :)


Possibly the Harvard Design 8-C "dual seal" cushion, a combination of the circumaural and supra-aural designs.  I don't have a ready reference for the JAN designation, but like you, I have seen them occasionally at hamfests.  


MC-162-A.  I think these are the most familiar to hams, since they were usually supplied with surplus earphones after the war.  They are profoundly uncomfortable because of the rubber hardness, and don't do a very good job of excluding outside noise, either.  I guess that's one of the reasons they were dumped by the millions on poor unsuspecting radio amateurs who may have thought they were getting "authentic" aircraft headphone assemblies.  Well, to be fair, they were getting them, I suppose - the cushions were just obsolete.   ;D


These NAF-48490-1 cushions seem to be the most common on the 'bay, probably because they became the Joint choice for quite a few years.

Ouch!  I had a feeling the headset had no cushions from your mention of Bakelite - that isn't easily visible from the ear side if a cushion is in place.  

I don't doubt you had ringing in the ears.  The power required from an earphone for normal speech comprehension is a function of the volume required to be excited by the earphone diaphragm, and that volume is effectively much larger without a cushion to contain the sound, not to mention the introduction of competing broadband noise.  You're fortunate that you didn't have a permanent hearing loss... :-\

I bought HS-33's with ordinary plastic earpieces on them and slapped surplus Chamois cushions from Fair Radio onto them back in 1972. I figured that they used these in the WW2 planes. Very comfortable. The H3 shot is from AAF site. HS-33's look similar when you put the cushions on.

Mike WU2D

Like the B-17, here is the radio op position in our C-47 paratrooper jump platform "Boogie Baby" located in Frederick Army Air Field, OK. BC-375, BC-348 on a reproduction table built by Fred WA5QAQ. The LS-7 is not installed but for ground demonstrations. Hoping to make some aeronautical mobile contacts soon!  :D

Nice ke5o!

Thanks John!
Here is a photo taken last Friday. You can see the HF antenna above the fuselage going up toward the tail.
73,
Steve

http://www.wwiiadt.org/ (http://www.wwiiadt.org/)