DATA DISCREPANCY PART N. 4231 FILTER CHOKES
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DATA DISCREPANCY PART N. 4231 FILTER CHOKES
I have a model 20. The choke was open. According to the Philco catalog from 1936, the resistance is 400 ohms. According to the information that appears in the library in its CHOKES section, a value of 4,000 ohms appears. Which one is correct?
One way to fix it is to rewind. Or replace a resistor with the correct value of approximately 4W.
What do you recommend? It's not easy to rewind.
I appreciate any information. It is important to correct the value if there is an error in the library.
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OK, thanks for pointing that out. I'll alert Nathan who manages the library.
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Other folks will have to comment on whether a resistor of proper value would be OK, I don't know. As far as replacement, I have replaced a filter choke with a Hammond choke in one of my restorations and it went just fine. Here's a link to the discussion on the 66B restoration. Terry (radioroslyn) does suggest a resistor replacement as you'll read in the threads but I opted for the choke replacement.
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OK thank you very much
Regards,
Ferran
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The circuit in the 20 is different than the 66 in that the 20 the choke is all of the HV @ 50ma or so. In the 66 it's just used for about a few ma up in the mixer.
When my pals were reading comic books
I was down in the basement in my dad's
workshop. Perusing his Sam's Photofoacts
Vol 1-50 admiring the old set and trying to
figure out what all those squiggly meant.
Circa 1966
Now I think I've got!
Terry
(This post was last modified: 02-01-2022, 07:06 PM by Radioroslyn.)
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Thanks Terry, I wasn't clear. I didn't mean that the choke I used would be the one for the 20, just that the Hammond folks do have chokes that could be used as long as you select the right one.
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I looked back at the original source Philco parts catalogs.
Philco 1933 parts catalog:
Philco 1936 parts catalog:
All of the later Philco catalogs (1937, 1938, 1942) that we source from also say 400 ohms.
I'd say that 400 ohms the correct value. For the Library Chokes table I've updated it to be that value too.
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hello Guys,
If I remember I am fairly sure that it should be 400 because I believe that what my 20 is.
Sincerely Richard
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This is the closest product I have found:
https://www.mouser.es/ProductDetail/Hamm...TtYRvn8nru
14H, 75mA, 429 ohm
I am concerned about the 75mA
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I would not be concerned about the 75 mA rating because the total power supply current drain of the model 20 is only 72 mA or less.
As shown in the attached service note chart, the total power supply current through the 80 rectifier is 36 ma per plate, for a total of 72 mA. The actual total plate current drain of the other tubes is only 48 Ma, the remaining current being dissipated in the bleeder resistor and associated circuits.
https://philcoradio.com/library/download...n%2036.pdf
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You are right. Thanks for the help. I will buy the choke.
Model 20 is one of my favorites.
Regards,
Ferran
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