The PHILCO Phorum
Model 41-221 pilot socket - Printable Version

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Model 41-221 pilot socket - electricroo - 04-27-2026

What is the difference between socket 37-9825 and 76-1177. As the schematic states to negate with modulation hum either install a .05uf capacitor across the pilot leads at resistor 4S, or replace the socket with part 76-1177. What is the difference between the two sockets?

Ron S.

RE: Model 41-221 pilot socket - klondike98 - 04-27-2026

Welcome to the Phorum!
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I don't know what the difference is between the two lamp sockets but suspect the new one might have a capacitance incorporated into it. The capacitor would be across pilot lamp leads at resistor 48 (the 8 looks like an S on the schematic seen at https://philcoradio.com/library/download/service%20info/yearbooks/1941/split/Part39-Philco%201941%20RMS%20Year%20Book.pdf ).

I did look in the 1942 parts catalog that we have in the library but did not see those lamp sockets listed.

RE: Model 41-221 pilot socket - DaleHCook - 04-28-2026

klondike98 Wrote:  I did look in the 1942 parts catalog that we have in the library but did not see those lamp sockets listed.

I have previously looked through all of the parts catalogs which we have, and I do not recall seeing lamp sockets in any of them.

RE: Model 41-221 pilot socket - morzh - 04-28-2026

It is probably the resistor 48; there is nno such thing as an Alphanumeric designators in the sch.

I looked at the sch of this radio (code 123) and at this point I do not understand how a 0.05uF capacitos across the pilot (it is #49) would do anything to the hum.
Introducing a ripple current that leads the current through the 53 Ohm by 90 degrees (and is lower by 3 OOM)...not sure how effective that would be.
But does not hurt to try....

RE: Model 41-221 pilot socket - RodB - 04-28-2026

Mike, that's exactly what the original designer said.

RE: Model 41-221 pilot socket - morzh - 04-28-2026

What? The ripple current out of phase?
The cap's impedance is such that it would not affect it that much.

RE: Model 41-221 pilot socket - electricroo - 04-29-2026

Well, it doesn't really matter but I was just curious about what the different socket was. My radio had the capacitor across the resistor. I did a total rewire including sockets and had to eliminate the field coil / choke speaker because the speaker was not on any condition to be used. I'm about to go through alignment then I will post a full video on the chassis restoration. In the meantime here's a 30 second clip of it working. Good reception in the basement even though the alignment wasn't done yet.
https://youtu.be/LyrYHvJR8AI?si=9hZFPxJfE40MgTTq