WD-11 vacuum tube base

I collect, repair, and restore antique radios. I have a few that date to the 1920's, and two of them - a 1921 W. estinghouse Aeriola Sr., and a 1924 RCA Radiola III (also made by W. estinghouse) used a tube called the WD-11. WD-11 tubes were poorly engineered - when they burned out, the filament often drooped and contacted the vacuum tube's plate, which had high voltages running through it (okay, not high by today's standards - 22.5 to 135 volts, depending on the usage), but enough to damage parts of the radio that were not meant to receive more than 1.5 volts or so. Later, RCA provided a service bulletin telling how to utilize the UV-199 tube in place of the WD-11 with some modifications and an adapter in the radio.

Needless to say,UV-199 tubes and adapters are rather expensive now, and as for WD-11 tubes, used ones that still work often sell for over $100, and collectors are hesitant to use them for obvious reasons! However, common CK5676 hearing aid/radiosonde tubes from the 1960's have similar electronic characteristics (if you solder a 22-ohm resistor across the filament leads to make the correct current draw), without the physical deficiencies, of the WD-11.

Most people using 5676 tubes either obtain WD-11 bases, or make a template to drill holes in the correct size and pattern in the bases of more common tubes, then use brass tubing of the correct size for the pins to fit the tube sockets in the radio. I decided to make it even easier, and used my Mendel90 to print WD-11 bases. 1/8" and 3/16" brass tubing would be soldered to the leads on the 5676 tube, then the brass tubing would be inserted into the holes in the printed tube base and held in with epoxy or super glue for added security. A cut-off 1" test tube would then be glued in over the 5676 tube for the appearance of the original tube envelope.

My boss did the drawing in Autocad with the dimensions I provided (I don't know how to use CAD software at all), then I used Freecad to convert the .igs file to .stl format and sliced it with Cura.

Nice! I used to do a lot of old radio restorations, too. 3D printers are great for replacing things like buttons and knobs that are lost/broken and hard to find.

I usually started with refinishing the cabinet, because if that wasn't possible, there wasn't much point in rewiring the chassis. It also provided inspiration/motivation to do the rewiring. I used to replace old electrolytic caps by taking the guts out of the old ones and installing newer, more modern, always smaller caps of equal or greater voltage and capacitance ratings. I also replaced all paper/foil/wax capacitors with polyester caps and then rewired with teflon insulated wire. Tested and replaced bad tubes, too, of course (I have a TV-7 tester I picked up at a swap meet for $50 before the tube audio nutz pushed the price on all things tube related through the roof). The final step was to tune up the set using the old service instructions from the Beitman's manuals. Most of the time I got them working as good or better than new.

Edited 1 time(s). Last edit at 03/14/2015 10:29AM by the_digital_dentist.

Good job! And....real radios glow in the dark and keep you warm and cozy at night.

Quote
the_digital_dentist
I used to replace old electrolytic caps by taking the guts out of the old ones and installing newer, more modern, always smaller caps of equal or greater voltage and capacitance ratings. I also replaced all paper/foil/wax capacitors with polyester caps and then rewired with teflon insulated wire.

I'm sorta off topic for this thread, but have a look at the latest issue of 'Nuts & Volts' magazine. There is a series running about restoring old radios and this month is how he reuses the old capacitor bodies. Interesting article.

And, to the OP of the thread - NICE JOB!

---

"I have noticed that even those who assert that everything is predestined and that
we can change nothing about it still look both ways before they cross the street"

-Stephen Hawking

Quote
the_digital_dentist
Nice! I used to do a lot of old radio restorations, too. 3D printers are great for replacing things like buttons and knobs that are lost/broken and hard to find.

I usually started with refinishing the cabinet, because if that wasn't possible, there wasn't much point in rewiring the chassis. It also provided inspiration/motivation to do the rewiring. I used to replace old electrolytic caps by taking the guts out of the old ones and installing newer, more modern, always smaller caps of equal or greater voltage and capacitance ratings. I also replaced all paper/foil/wax capacitors with polyester caps and then rewired with teflon insulated wire. Tested and replaced bad tubes, too, of course (I have a TV-7 tester I picked up at a swap meet for $50 before the tube audio nutz pushed the price on all things tube related through the roof). The final step was to tune up the set using the old service instructions from the Beitman's manuals. Most of the time I got them working as good or better than new.

Funny, I tend to do exactly the opposite - I figure if I can't get it working, it's not worth restoring the cabinet! My tube tester is a Heathkit a good friend of mine (and also my ham radio "elmer") gave me, along with my HW-101 HF transceiver. Love Heathkit stuff - it was generally sturdy, and made to be owner-repairable!

Don't the tubes get a bit on the hot side for fdm plastics? I seem to recall my tube bases are ceramic/porcelain.

Ah - ignore me. These are tiny signal tubes with very low power heaters. I was thinking of power tubes for my audio amplifiers - a different sort of animal.

Edited 1 time(s). Last edit at 06/02/2015 09:12AM by JamesK.

Yup, HUGE difference between a 5676 pencil tube running 1.5 volts on the filament and 45 on the plate, and a UV211 transmitter tube running 10 volts on the filament and 1kv on the plate!!!