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#1
12-26-2019, 07:03 PM
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Homebrew help
I need some help with a family battery radio I brought back from Illinois. It was my uncles homebrew build in the 20's. I cleaned it and the coils have continuity. Rehostat is cleaned and around 10k. I presume it was a brass 01A tube which I will find around here. Grid leak is open so I need to find its value. Cap underneath is unknown for now. May be .0005. I also presume the four posts at the top (could not get the photos to go L>R) are power.
If anyone can ID the proper connections, I have an ARBE and an AM xmtr to try to make it work for the first time in 90+ years.
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“Once you eliminate the impossible...whatever remains, no matter how improbable, must be the truth." Sherlock Holmes. Last edited by Dave A; 12-26-2019 at 07:13 PM. Reason: text 
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#2
12-30-2019, 02:18 AM
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Grid leaks were usually 2 meg ohms, with a 100-500 uuf cap.
Are you 100% sure about the pot? 50 ohms would be more suitable for adjusting the filament current of an 01A, which it appears to be wired to do. I am still scratching my head, perhaps it serves another function, such as regeneration control  Do the wires from the coils feed through 6 small holes in the board directly underneath them? Is there any evidence that there ever was a tuning cap in the circuit? Sorry, more questions than answers at this point, jr
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#3
12-30-2019, 04:44 AM
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Hi Dave,
I took a couple of pictures from an old copy of " Radio Simplified " published in 1923. These drawings are very close to what you have. I traced out your wiring and it looks like the tuner is missing and maybe a .001 cap across the head phone terminals. Use 45 vdc for B+ and 6 vdc for filaments. If the grid resistor you have is shot just use a modern one like Jr Tech mentioned. I used to use 250 pf for the cap and 2.5 meg for the resistor. Your circuit is regenerative. Your little radio looks like fun.  A tuning capacitor would connect at the unlabeled green line and ground connection side of your radio. Verify that the filament lights before connecting the B+, just to play it safe. Headphones should be 2000 ohms or greater. Ed Last edited by EdKozk2; 12-30-2019 at 05:11 AM. Reason: revised schematic
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#4
12-30-2019, 12:27 PM
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jr, ed...looking good. The 1923 honeycomb version looks just like what uncle worked from. The honeycomb wires do go through the six holes. And the missing tuning cap makes sense on the two side posts. Long gone so a search begins. Finding a desktop version would be great. Kutztown will help. I put a 2meg resistor under the .0005 cap for now. And the pot is really 20 ohms. Bad meter first time. I'll use a 201A for now. Thanks for the help!
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“Once you eliminate the impossible...whatever remains, no matter how improbable, must be the truth." Sherlock Holmes.
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#6
12-30-2019, 09:14 PM
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init...thanks for the note. It is a great thing to look for at Kutztiown. I am trying to keep this restoration to the uncle construction of the day. The family did have $ in the day (early 20's) and an automotive parts shop which I think he drew on for his parts. Auto shops in the day did sell radio parts. Kjellstrom Auto Parts on 7th St., Rockford, IL
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“Once you eliminate the impossible...whatever remains, no matter how improbable, must be the truth." Sherlock Holmes. Last edited by Dave A; 12-30-2019 at 09:17 PM. Reason: text
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#7
12-31-2019, 08:24 AM
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Hi Dave , just so you know , If the resistor I have (as a display model only) was any good I'd have offered to send it to you for your project , but it is defective in that it doesn't vary the resistance smoothly . Pulling/pushing the plunger with an ohmmeter attached shows the meter's needle fluctuating excessively like the classic dirty potentiometer , just what you don't need in your grid leak circuit .
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Linear Mode
