Philco 20 Cap Values - 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: Philco 20 Cap Values (/showthread.php?tid=23005)
+- 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: Philco 20 Cap Values (/showthread.php?tid=23005)
Philco 20 Cap Values - wabr101 - 11-16-2021
It's been discussed many times..but..
My 20 has the 1 1 1.5 and .13.
I used the 20a values os 2 2 1.5 and .47.
The original can was still in spec with one cap measuring .8 instead of 1.
Normally going over a bit makes for less hum..but others have mentioned higher voltages for this early power supply..that and the choke..field coil etc..it seems finely tuned.
Most who add higher values do 4 6 8 or 10.
I uses the 20a values good for 25-60 hz.
That said should I open the can ans replace the 2 with 1 etc...
Thoughts? Will using 20a values raise the voltages that much? Hum was minimal before rebuilding cap can. I have not tried it as speaker is getting reconed.
RE: Philco 20 Cap Values - mikethedruid - 11-16-2021
From years of experience, I wouldn't worry about it if those, the second numbers mentioned, are the values you used. If you're worried measure the plate voltage on either of the 71A output tubes to terminal 1 of the condenser block. Perhaps someone else here can give you the exact voltage to look for, but here is the spec sheet for the tube, https://frank.pocnet.net/sheets/021/7/71A.pdf . My guess is the voltage you are looking for is about 135 volts, no less than 90 nor more than 180.
RE: Philco 20 Cap Values - morzh - 11-16-2021
When using larger cap vale in the rectifier filter (the very first cap after the rectifier tube) you will end up with higher rectified voltage. This might make tubes run hotter.
Other caps (after the choke) are indeed not as important.
20A used higher values to compensate for 25Hz. But give it 50Hz and the average voltage goes up.
RE: Philco 20 Cap Values - Steve Davis - 11-17-2021
Remember your 25 cycle radio is now a 60 cycle radio. Higher value film capacitors are available at a reasonable price. I would use a 1.0 for the first cap after the rectifier and increase the value of the rest, except the cap across the choke. That cap, should be the value shown for the 60 cycle radio or better yet, delete it. Using a larger value here can actually increase the hum.
Steve