RF Cafe Software
About RF Cafe
1996 - 2016
BSEE - KB3UON
RF Cafe began life in 1996 as "RF Tools" in an AOL screen name web space totaling 2 MB. Its primary purpose was to provide me with ready access to commonly needed formulas and reference material while performing my work as an RF system and circuit design engineer. The Internet was still largely an unknown entity at the time and not much was available in the form of WYSIWYG ...
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At the left is a photo of a 1941 Crosley Model 03CB floor model radio. This one I restored a couple years ago, but I restored another one 20-some years ago, which was given as a wedding present to my sister-in-law (Melanie's sister).
Robin Sparkes just checked in with a Capehart Radio restoration project that he is getting ready to undertake. Please click on the link to view his page. Maybe you can provide some assistance.
Here is a page of links to companies that provide restoration services and parts.
Paul's Tube Radio Restoration website has lots of good photos of restoration processes.
RF Cafe visitor Bob Davis, whom I have known for many years, recently sent me (at my request) photos of some of the antique radios that he has restored - it is one of his hobbies. That these radios are still available is a bit miraculous since Bob lives in New Orleans, very near the levee system along Lake Pontchartrain. Fortunately, his home was on higher ground and was spared the worst of the flooding during Katrina. Here are Bob's restoration stories for his Midland and Lloyds shortwave radio, his RCA 86T, and a few other radio restoration projects.
RCA 86T Restoration Project
This is a really nice, art deco looking set. I got it from a friend. It's on the list to restore, but haven't found a really good schematic for it. I turned it on so you could see the dial. It hums a bit, so I'm worried that the caps may blow up.
Read Bob's complete write-up on the 86T restoration project.My Christmas  holiday project was to start restoring my RCA 86T radio.
This fellow came to me through a friend of a friend as a forewarned basket case. For the 50 bucks I gave him for it, I didn't care what I had to do to it (at the time my car took more than 50 bucks to fill up!).
I took a few pictures showing the dangers of just connecting one of these old fellows up to the AC mains and going for it (they were on a current limited power supply, with one hand holding the camera and the other poised over a kill switch).
I wonder how many people buy these old sets off of the internet or antique shops and are told they are "re-capped" and ready to go without such obvious hazards like these repaired? Heat and rubber coated wire + 70 years = fire! Cloth covered wire gets brittle too, as one of the pictures show.
There are many businesses where competent folks sell radios that are refurbed safely (and professionally). Some auction sellers One will find on the popular sites are amongst that number. Be careful to check credentials and get a few referrals before you buy unless you're going to gut and rebuild the radio yourself. The pro's will be happy to show off their work, with pride. Whatever one does, a disassembly and a safety check beneath the chassis of any old set one may buy is good advice before plugging it into the wall. It may be pretty on the outside and not be so pretty underneath the chassis.
Airline 62-437 "Movie Dial"
Here is an Airline 62-437 "Movie Dial" tabletop radio from the series that was sold by Montgomery Ward in the 1930s. It uses a self-rectifying vibrator DC-DC converter for changing 6 Vdc to 145 Vdc. See a complete article on the restoration here.
This is a wonderful set, circa 1936. It has been fully restored. The magic dial glows in the dark ready to navigate the user around the world. It has a wonderful tone and is a real DX hound.
Post WW2, late 1940's. This set is a little unique. Most you will see have the 8 pin 50L6 output tube. This one uses a 50B5 which is a newer mini tube amongst the locking 7 volt filament tubes (fun to get those out of the sockets). This unit came to me in a shopping bag with about 5 coats of various types of white paint on it and many insect nests in it. Every wire in it had to be replaced as they all crumbled when I flexed them. About 100 hours in this little girl. I stripped off all the paint to reveal a beautiful, "swirly" cabinet.
You can still pick these up on eBay once in a while for under $100.00 (make sure you restore them or they have been restored if you want a player, their wiring and their capacitors don't age well). This one probably isn't worth the $300 some of them go for totally restored, but it was owned by my Uncle Pete and it was the first radio I remember that could get AM stations in Iowa that were farther away than any other radio I had access to at 6 years old. Let's just say it HAD to be restored as it helped to launch a long career of yours truly making sensitive receivers for a living.
They call these "Hippopotamus" radios, one can see why with a quick look at the face.
Bendix Model 75P6U AM/FM
"A late 1940's Bendix AM/FM set. Now that she's all re-capped and re-tuned it's a very nice receiver. Look at how labor intensive the wiring is underneath. This one would have survived a Russian attack for sure... I still have a little cabinet work to do. Trying to find a good pinstripe brush to re-do the frequency dial where the paint wore off after 60+ years."
This is the next challenge for restoration. Say...where's the FM dial?
Nice little set. Dual band unit pre WW2. Best I can tell from what I've seen it was around 1939. I'm sure someone will tell me exactly (the Riders diagram on this one doesn't have a date).
I had one of these when I was a kid and it was an AM DX hound. The TC-62 had a extra tube in it for an RF amp over the other, cheaper set that looked identical to it. The tube wasn't too well shielded however and the radio would squeal if you got the signal strength and the tuning cap just right (which was pretty cool to a 7 year old). Neither of these have that issue as I shielded the tubes.
I like these not only because they remind me of the one I had (that my Dad gave to me when it was retired from the kitchen counter) when I was a kid, but they also have some nice 1950's styling. These are circa 1954.
I bought this on eBay and brought it back to life thanks to the BAMA site I see you have a link to on your site now (wow, great folks who provide the schematics for us). I went through it with a fine tooth comb and refurbed all the electronics with new caps etc. and then did a full re-alignment on it using my fancy test equipment. It's a real player and a fine shortwave set. If you look, there is quite a bit of band spread across the dial (i.e. the frequency change versus dial travel is small), makes it really nice to DX with.
Bob says: "I'll probably have a really neat one for you in about 3 months Once I get it restored. It uses a projection system to display the station Information, they call it a 'movie dial'.
If you take this further, perhaps a warning on your hobby page that if you buy one of these things (especially off of eBay) have it inspected by a qualified tech or rebuild it yourself Or you may burn the house down. I don't quite know how one would word that, but It's probably a good idea. Old caps explode, old cords are frayed and short, transformers short And the insulation starts on fire, you know, cool stuff! Also a note about knowing what you are doing, using an isolation transformer and variac so you don't kill yourself or set off an explosion hitting 70 year old caps with a 120 volt (or higher) transient by just plugging the radio, in may be an idea.
I worked on an old Aetna radio a few years back and the IF cans had 200 volts on them, ouch!"
Here are some pictures of some of the radios I have. All but the White Capehart and the Wards Magic Dial have been gone through thoroughly although I haven't done the full cabinet restoration on most.
I usually concentrate on the insides and bring them back to life and make them safe. I leave the cabinet collecting to the collectors. I just do this for fun, and to re-learn some of the old secrets the RF engineers of the past used to make these radios use fewer parts but still perform so well.
I will say it is fun to tune them up with my Rohde and Schwarz test equipment. The engineers who designed these never could have foreseen a 7 GHz spectrum analyzer and a 3 GHz high fidelity signal generator aligning their sets I am sure.
Well, that's about it for now, I have a few hangar queens that I'm working on, namely a 1936 Wards (Wells Gardner) "Movie Dial" set and a 1931 Westinghouse/Philco grandfather clock radio. Both are real basket cases, but will soon be back in shape. I hope you found this interesting.
|Kirt Blattenberger's Radio Restoration|
This 1941* Crosley floor console radio model 03CB was given to me as a Christmas present in 1983 by my wife, Melanie. It was found by my sister, Gayle, and her husband, Mike, in a barn on Kent Island on the Eastern Shore of Maryland. It sported a couple shortwave bands and AM (no FM in those days). Unfortunately, I did not take any detailed pictures of the unit, so the best I could come up with is this shot of my two children (Philip & Sally) sitting with my father-in-law, Marlet Goodwin, on Christmas day of 1990.
Its original finish was peeling off, and all the metal parts - the dial and trim plates, electronics chassis, etc., was rusting. It sat in our house for a couple years and then I tackled the refinishing project. Every bit of of the stain and shellac was removed from the case, and paint from the metal parts, using naval jelly (the good, caustic pink stuff). Hours of scraping, filling and sanding took care of the wood, and then a Minwax stain was applied, with a top coat of a few coats of Deft lacquer. The dial was carefully cleaned and lacquered. The dial trim plate was primed and painted gold (the original color). I removed all the tube and primed and painted the chassis gray (its original color). All the paper capacitors were replaced, and the tubes were tested on a portable tube tester that had been given to me by überengineer Jim Wilson. Only a couple needed replacing. Those were the days before eBay and the Internet, so finding replacements took enlisting the help of Ham friend who found them at a Hamfest. The antenna was a solid rectangular coil that ran around the rear outside edge of the entire chassis.
After doing a good visual and continuity check of the electronics, I plugged the radio into the wall. No smoke - that was a good start. A beautiful warm glow appeared at the base of all the tubes, and before long there was a welcoming 60 Hz hum coming through the huge electromagnetic speaker (no permanent magnet). I turned the dial and, voila!, the local AM stations came in clear as a bell (well, as a bell with a 60 Hz hum). The hum was eventually tamed by adding a couple caps across the coil. It probably killed some of the bass, but who would notice on AM? I pushed the "Japan" button and picked up some foreign station, but it definitely was not from Japan. Similarly, other far away broadcasts were received on the other bands, but I cannot recall the details.
Melanie and I gave the radio to her sister as a wedding present in 1993, since her sister's home was decorated in a Victorian theme. It has since, shall we say, "moved on," and I now have no idea where it resides. Oh well, that's the risk I took in gifting it. Here are a few of my other projects.
* I originally had 1926 as the year since I remember seeing the date on a label inside the radio, but research has shown that it is most likely 1 1941 model. The 1926 date was probably for one of the patents listed.
- 1941 Crosley 03CB Floor Console Radio Restoration Project
- Tesslor R-601S Vacuum Tube Radio Teardown
- Tesslor R-601S Retro Vacuum Tube AM/FM Radio w/Bluetooth 3.0 Modification
- Crosley 03CA Floor Console Radio for Sale
- 1941 Crosley Model 03CB Radio Photos (Tim O.)
- Radio & Electronics Restoration Projects
- Vintage Ads with Science / Technology Themes
- Vintage Magazine Ads from Duke University's Ad*Access Website
- Vintage Radio Control Systems