Emerson 25A Cap to drop voltage - Printable Version

+- The PHILCO Phorum (https://philcoradio.com/phorum)
+-- Forum: Philco Radio Discussions (https://philcoradio.com/phorum/forumdisplay.php?fid=5)
+--- Forum: Philco Electronic Restoration (https://philcoradio.com/phorum/forumdisplay.php?fid=8)
+--- Thread: Emerson 25A Cap to drop voltage (/showthread.php?tid=26245)

---

Emerson 25A Cap to drop voltage - GRG - 01-30-2026

I was reading this thread https://philcoradio.com/phorum/showthread.php?tid=18900 .  Radioroslyn suggests using a  6.8 mf cap to replace the  R7 305 ohms voltage droping resistor.  See attached schematic.

I have two questions, 1) My line voltage is 120V so should I use something greater? 2) I assume the cap is non-polarized, is that correct?

Thank you.

---

RE: Emerson 25A Cap to drop voltage - radiorich - 01-30-2026

Hello Glen,
Well Here is a link to the math formula and talks about dropping capacitor.
Yes a Non-Polarized capacitor like a film capacitor can be used.

https://www.vintage-radio.com/repair-restore-information/valve_dropper-calcs.html

plus here is link to ARf forum about radio using 

https://antiqueradios.com/forums/viewtopic.php?p=3934848&hilit=line+dropping+capacitor#p3934848
Sincerely Richard

---

RE: Emerson 25A Cap to drop voltage - GRG - 01-30-2026

Excellent, thank you!

---

RE: Emerson 25A Cap to drop voltage - morzh - 01-30-2026

yep, exactly 6.8uF for 120V AC.

---

RE: Emerson 25A Cap to drop voltage - GRG - 01-31-2026

Installed the capacitor voltage dropper with caps on hand (made a capacitor bank with 2 x 3 uF and 2 x .4 uF). Also added a 100k discharge resistor.  The radio is working well and cool as a cucumber. 

Thanks again gentlemen.

---