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Capacitor Identification Needed For A 1935 Zenith 970A Radio
#2

Hi Paul,

First off, welcome to the Philco Phorum, a phamily phriendly Phorum phull of Philco phacts and phine pholks (See a pattern here?).

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Now to your radio.

The capacitor is identified as C10 on the schematic and is a cathode bypass capacitor for the triode 2nd AF (driver). It appears to be a 5uF 25V electrolytic capacitor. The 1st audio amp tube, also a 56 has the same size capacitor between its cathode and ground.

Considering the age of this set, I would definitely replace this and all electrolytic capacitors and all capacitors for that matter especially the cap across the plates of the 2 outputs and from the plate of one of the output tubes to ground. It is critical that the electrolytics be replaced because as they age, they either open (causing hum) or short (causing really bad things like blown rectifier tubes or worse, blown power transformers). Same with the plate bypass caps for the output stage.

The set has a radio-phono switch, according to the schematic, which makes it ideal for playing back old-time radio recordings off your computer, MP3, CD player, iPhone, etc. The amplifier in this set is no slouch. I suspect it is a Class AB 2 and may be good for as much as 10 watts or more.

Hope this helps

"Do Justly, love Mercy and walk humbly with your God"- Micah 6:8
"Let us begin to do good"- St. Francis

Best Regards, 

MrFixr55


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RE: Capacitor Identification Needed For A 1935 Zenith 970A Radio - by MrFixr55 - 11-29-2025, 01:40 AM



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