Monday, September 5, 2011

1920s Radios A Hobbyist Observations

I got interested in 1920s radios by listening to my father as a boy talking about the first radio the family owned. It was an Atwater Kent he always said. He even remembered it ran on some sort
of batteries. Of course he couldnt remember much detail as he was born in 1924 making him
pretty young to remember much. For many years I wondered about these radios. What did they look like, and how did they work? I knew nothing and nobody that could help me.
Then came E-Bay! There they were for sale in pretty descent quantities.
Good grief they were even affordable. Im not a rich guy at all but just a working class guy
that happens not to really need another expensive hobby. I had never even bought anything on E-Bay! To make a long story short I found a Atwater Kent radio circa 1924 and bid $102.50.
I won the thing. My goodness what had I won I wondered as I waited out the 2 weeks for it
to get here. I found a schematic, refinished the beautifull REAL mahogony cabinet. It was fun.
Finally I bought a power supply to eliminate the need for all the batteries. Hooked it up AND
absolutely nothing. Wow what a disappointment! But wait, there was hope. I found an Atwater
Kent forum on another site with troubleshooting help. I found a audio transformer open and replaced it along with a couple of other parts and tried again. If you get into this hobby and are not a
electronic genius (very few are and that includes me for sure!) rest assured there are some
rather simple approaches to finding the problems.
TECHNICAL CONSIDERATIONS
ALWAYS check your audio transformers and replace them if you have to. Buy a simple ohm meter at radio shack. Check the primary and secondary winding for an open. Usually you will find a relatively low ohm reading on the input or primary and a relatively high reading (several thousand ohms) on the output or secondary. The exact numbers arent critical but the continuity must be there. Every set has its input voltages (90,22 etc) Make sure you put ALL the proper voltages where they belong. MARK THE WIRES! Remember that if theres a AC plug sticking out the back then I dont own it! This means lots of wires to the power supply. There were standard colors in the 20s, but who cares. Any good stranded wire will work BUT dont mix the spaghetti farm up or you will be buying more parts. By the way, if your going to get into this hobby for any length of time buy a ARBEiii typeregulated power supply on E-Bay. Yes I know they cost a little over a hundred dollars or so but spend the money. If you hook one of those type power supplies up and theres a short it will simply shut off the power until you hopefully fix the problem. They are well worth the money! As a quick safety note KEEP YOUR PAWS OUT OF THE POWER SUPPLY. These old radios can run 180 volts at times. Now dont get scared away from the hobby. TURN THE POWER SUPPLY OFF before tinkering around. gemon sense rules this hobby. Expect different voltages on different old radios and supply them accordingly. Once they are hooked up and working its a no problem deal. Give the radio a reasonable antenna (20 foot copper out the window minimum) and provide a simple ground (small piece of copper pipe drove in the ground outiside the same window). It should work fine as modern AM stations have a lot more power than in the 1920s!
All your power sourcesusually go through thetransformers to the plate of the tube. No continuity no path to tube and you guessed it nothing works.There will be RF transformers as well but they are not often as big a problem as the audio transformers. Try to leave the RF transformers in the first several stages after
the antenna input alone. They are delicate and of light wire. Usually they are ok if undisturbed. Neutrodynes are great radios as well ,but beware the interconnecting circuitry in the first several stages. Again, if its got continuity as in your schematic leave it alone. Before you power anything up be sure to measure between ground and your input voltage terminals. If theres a short STOP dont power anything up until you find the problem. Capacitors are the first suspect in a short situation. Make sure yourcapacitors are rated for the voltage applied. Slightly higher values of capacitance are acceptable if you cant find the exact one, and expect them to be much smaller in some cases.
Leave the old capacitor in the set if removing it seems inappropriate. Just remove its electrical connections entirely.
DOES YOUR GRID LEAK RESISTOR LEAK?
The small cartridge mount device you see in many old radios prominently displayed is your grid leak resistor. These things are mounted for easy no-solder replacement. That should be your first clue. Replace it if it doesnt read correctly. They usually read up in the meg (million) ohms so you must change to the high scale of your ohmmeter. Its best done with the resister removed. This is the number ONE cause of 1920 radio failure! If you dont like the look of the modern replacement solder one the bottom out of sight! These things carry little power so even a quarter watt rating will work and try to get as close to value as you can per schematic. Also be advised that Zenith actually put in some real fuses in those days that are snap in cartridge fuses. Please dont confuse a grid leak resister with a fuse. If you replace the fuse make sure its the same amperage rating.

BAKELITE
That black front cover may very well be what is known as bakelite. One of the first things to know about antique radios is DONT DROP THEM. Bakelite cracks! Can you fix the cracks? Well maybe but its easier to be carefull and DONT let the chassis slip out of your hands and fall cracking a corner for example. Use both hands when turning the chassis over for inspection and always hold firmly with one hand. By the way ,CORNERS of wooden cabinets and bakelite boards are very prone to breakage. I always check the corners on a prospective purchase of the case and boards. DO NOT OVERTIGHTEN chassis screws as you will CRACK the bakelite. If you break it buy some good epoxy and good luck. With any luck you can hide the repair, but this then begees an art and not a science. Bakelite came in limited colors so perhaps a clear light epoxy will put things back together again. Humpty Dumpty could NOT be put back together again. Try not to get in the broken bakelite problem if you can avoid it. For polishing bakelite there are a lot of people selling a lot of chemicals out there. Clean it well with a wet soft foam swab (or a bunch of them) and take your time removing all the dirt you can at first. Water is a solvent, but a mild one you know. I use Brasso after that and gently polish the bakelite to its original gleam. Dont over do it and use a soft toothbrush to get into the small places around the knobs and decorations that you cant get to otherwise. Get all that white residue out of the crevices , and DONT remove lettering or decorations on the bakelite. Be carefull to get the BRASSO ONLY on the bakelite areas.
Chassis styles
Be AWARE of chassis types and styles BEFORE you buy a 1920s radio. How will you remove the chasis to work on it? Some gee out the top. Some gee out the back of the set. When you remove the chassis screws place them in a clearly marked bag like a CSI detective so you will have them when its put together time. Make sure when you remove the chassis you WATCH OUT FOR THE RF COILS! They are of light contruction on light forms and easily damaged. They can broken by hitting the wooden case. Some chassis construction is Bakelite such as some of the earlier Atwater Kents. RCA used a lot of metal chassis contruction. Zenith also liked metal chassis.I found easy grounds avialable in a metal chassis a plus, however I really hate removing rust! Metal parts that are removable can be removed and soaked in JASCO to remove rust overnight,but non removable parts are a problem requiring a steel brush. Its a lot of work to remove rust. I avoid buying a set with a lot of rust. I suppose its a personal preference. If you do remove rust with a brush be sure to use a little clear lacquer where appopriate for future protection. Be carefull NOT to get clear lacquer where it will NOT CONDUCT such as on electrical contacts!
WHAT DO I DO ABOUT THIS OLD WIRING HARNESS?
When you choose a radio to restore from the 20s remember they will probably be battery sets.Usually the case will have multiple holes in the back for all the wires to enter and hook to terminals hopefully marked inside. There are basicly two styles. The type you ID and connect the wires to terminals and the second type (sometimes used by RCA and others) where the wires are physically soldered somewhere deep in the recesses of the chassis. You WILL spend a lot more time replacing a wiring harness that is soldered in the chassis. I would NOT recgeend it for a beginner unless you have a lot of soldering experience. Start out with a chassis that you simply hook up your own wires through the holes and to the power supply,antenna and ground. When you take on the challenge of the wiring harness remember you will need multi-colored wire and ID each one meticulously.


DO MY OLD TUBES WORK?
First the good news. If they are intact and have good filamints (thats the two large pins on the bottom of an 01a tube) then theres a good chance it will work. If you buy tubes from a reliable source that tests them for functionality with a tube tester its a much better possibility. This is NOS (new old stock) folks so you probably wont find a source for new 01a or 112 (12a) amp tubes. If you have one good radio simply swap the tube for a known good as a basic functionality test. Let it run for a good long time and listen for problems. If the tube arrives with the glass top ajar (loose)but still basicly a sealed intact glass tube DONT THROW IT AWAY. Simply epoxy the top to the bottom and you may still have a good usable tube. Expect to pay about $10 for a good 01a tube. They dont give them away! 12a tubes are usually used in the last stage as an amplifyer. It will probably operate with a higher voltage on its plate such as 135 volts and feed your speaker or horn. Basicly your going to want a lot of good 01a tubes and a few 112a tubes. RCA,Cunningham,or other major manufacturers made these tubes by the thousands and all will work well so buy what you find at a good price for a good tube. Shipping can easily and safely be done with wrapping the tube in bubblewrap and surrounding with peanuts in some quantity. You should NOT lose a lot of tubes in shipment. Yes I know they are GLASS. DO NOT SHIP THEM IN THE RADIO SOCKETS! You will be vacuuming glass shards from your new radios insides.Take the tubes out and pack them well! Make sure you purchase 01 "A" tubes and not for example a 201 without the "A" designation. The earlier variants without the "A" draw a lot more current so try to avoid them if possible. BEWARE of "tube stuffers". Tube stuffers sell radios with ANY type tube in the socket whether it is correct or not. Read your schematic and put in the proper tube only!
DOES MY ON/OFF SWITCH WORK?
Yes it moves still but does the corroded old thing still work? Easiest way to tell is to first measure for continuity to ALL the filaments of your tubes. Each tube must have a plus and minus 6 vdc available to "light up" and perhaps glow a little red filamint. For those in the know thats called the "A"supply or A battery. If NONE of the filamints have continuity jumper out the main on off switch and measure again. (You will have to then turn off your power supply to shut down or disconnect the battery for control). If you still have nothing everywhere check the rheostats inline with the tube filaments.If they are open they could also be the culprit. There are usually two rheostats (or more) that control tube gain through their resistance and resulting voltage applied. Replace if neccesary. Try again until you have 6vdc where you need it! Follow your schematic to connect voltages together when required but keep clearly in mind that you can never directly short a supply voltage. For example,dont directly short A- to A under any circumstances. For most of my old radios I simply leave the aging on/off switch ON and control ON/OFF with the power supply. After all, these old switches are pretty much aging mechanical devices with increasing usage of the switch leading to eventual failure. Just leave it in the ON position but for safety reasons DONT FORGET! Begee accustomed to turning the radio On and OFF with the power supply.
The ABCs of Batteries
A is filament. About 6.2 volts usually works. In the old days any old tractor battery put out 6vdc.It was used for the filaments (,25 amp per tube) so it went dead first. Kinda like a light bulb. They draw a lot of current. For fun get the tech specs on a RCA 201A and read the parameters.
B is plate voltage. Used on the plates of the tube. Its a high positive potential about 90 vdc usually. The grid of the tube usually operates with a much lower negative voltage applied. B voltage can be 67 0r 45 volts as well. Follow your radios schematic. It is only about 50 milliamp so the B battery will last a while.
C is used on the grid of some but not all radios. Usually a NEGATIVE 4 or 9 vdc to the grid. Some sets simply put the negative 6 vdc of the A battery on the grid SO DONT BE SURPRISED IF YOUR PARTICULAR RADIO DOES NOT HAVE C BATTERY. I recently rebuilt a beautifull Stromberg-Carlson 1920s radio (my favorite by the way) and found the original C battery still clamped under the bottom of the beautifull wood cabinet. IT would have NOT been easy to get to so Im assuming they lasted a while! It was a 4.5 volt C battery. Surprisingly it still measured 2.5 volts. Not bad for 80 years!



WHAT ABOUTTHAT BEAUTIFUL WOOD CABINET?
Ok heres the secret word. FORMBYS. Go to Lowes and get the face lift kit only if you can,however if you must re-finish they sell the re-finisher as well. IT STINKS and is a caustic dirty mess so dont cheap out and NOT buy the rubber gloves. Do this job outside and take your time. Its a lot of fun actually and very rewarding to find that beautifull Mahogony finish hiding under 80 years of dirt. Horizontal surfaces are the dirtiest. Do you have an air gepressor in the garage? PUT ON A MASK FIRST AND EYE PROTECTION and blow it out first. Air wont hurt things too much if you keep your distance from the RF coils etc. Old varnish flakes into tiny scales so use care not to get them in your eyes! Bottom line is take your time and enjoy the woodworking end of this hobby.Check your corners. Use epoxy and a large clamp to hold the corners while they dry. Finishing nails can be fairly easily hidden by insetting and covering if the old box got damaged in shipment.
WAIT! I DONT HAVE A SPEAKER
Ok your going to have to buy a high impedence 1920s speaker. It should usually measure 1800 to 2000 ohms , but its not critical. It should NOT measure 8 ohms like a modern speaker. Peerless is my favorite speaker. Beautifull wood and sounds almost as good as a modern day speaker. 50 to 100 dollars plus shipping would be a fair price. A lot of folks have no idea if they work. A low voltage battery applied shoud provide a "popping or clicking" noise if its got a chance. That test does NOT guarantee fidelity! Atwater Kent E-2s are good as well as the RCA 100 series A or B. I think the RCAs sound good as well and are inexpensive. If you want a horn buy one. Everybody buys at least one horn. They are cool to look at but thats about it as far as Im concerned. They are kind of "tinny" usually but you might enjoy seeing how they are constructed. AK horns had a pot metal base except the "M" model so if you buy a AK look for a "M" model. Dont refinish horns unless the rust factor is really bad. They usually hold up fairly well over time if stored properly. TRY to NOT accidently pull the little connection "pins" off the wires. They are disigned to plug inon your equipment connections. Good luck on E-Bay to find that perfect speaker. RCA for RCA or AK for AK is a cool display but you can mix and match! Like I said earliler I prefer the Peerless with all my radios!


FOR THE VERY SERIOUS COLLECTOR
Buy Marconi and Deforrest. They hold value well.
However, do NOTHING to them or you will probably degrade the value. They are truly collectors items for display. Now Im wondering "wheres the fun in that" but to each his own.

After 80 yearsmy AK 20 radio came to life before me. It was a lot of fun to turn the old knobs
and hear it work perhaps just like my grandfather had for my father as a boy.
Yes the new transformer is in there and a few new parts hidden in the depths of the radio, but it
didnt matter. Its a living thing of sorts to me. It sits beautiful on the shelf and plays well.
This thing isnt about auctioning something at Sothebys. This is about the satisfaction of
making the old beasts gee alive and see how they worked and were designed.
Its also about sharing it with others.
Operating as philtechltd here on E-Bay I watch and buy the old beasts.
Each one must be made in the 1920s- nothing newer. I like the beautifull wood cabinets,and
am not shy about refinishing. (remember its NOT going to Sothebys!) Its my radio and if I want
to re-finish it I do so. I intend to keep the old beasts. Not re-sell them. There is no profit in
this hobby, just self satisfaction!
I am picky about the appearance however. Its got to be unique in some way.
Different models with different engineering behind it. You can see it and touch it.
Made in AMERICA when anybody could attempt to build a radio!
The varieties are endless. If I could replicate the most gemon models one would find
in a radio store in 1925 now there would be a feat worth pursuing.
I dont bid on earlier or later vintage equipment. Its got to look like a radio not lab equipment.
Its got to look beautiful on the shelf as a work of art. TRF or Neutrodyne ONLY.
NOT a superhet to be found in my collection. If you want a superhet go to Walmart and buy
a plastic one from China for $5.
So thats about it for a simple hobbyist I suppose. I am forever searching the 1920 battery radios
on E-BAY (OH by the way ,batteries ONLY nothing that worked on AC in my collection as thats
much too modern!) for that next 1920s radio that I might could afford.
The only other requirement that I have is pretty simple.
They must be restored to WORKING order. I repair them all.
You can actually listen to them on a horn or era speaker.
After all, if your buying a radio in a 1920s radio store would you buy it
if it didnt work?
Youd want to listen to it wouldnt you? Probably listen to several before paying
out your hard earned money and choosing the best.
So over at philtechltd were still putting together the old 1920s radio store.
One radio at a time and as the money is available.
Someday maybe we will buy a set that uses 110 volts.....but I doubt it!
Thanks and Enjoy the hobby
Phil Holtam
philtechltd
Alll rights reserved 2006

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