03-13-2017, 03:05 PM
(03-13-2017, 02:50 PM)Steve Davis Wrote:Quote:Don't use electrolytic's in the filter can, use 630 volt poly caps.
I have read this many times but, I don't understand why. When I look at the 20 schematic, I see the power supply is virtually identical to the one used in a 70 or a 90 or just about any of the other Philco models. So why are electrolytic capacitors OK in a 70 or a 90 but not in a 20?
Steve
There is one big difference if you look at the values of the caps the 20 uses much smaller capacitance. Electrolytic caps in these small values don't hold up well. I replaced the caps in my 87 which uses these small values w/ 4.7mf@ 450v (two in series to give me about 2.3mf @900v). Lasted about 4 month and the input cap shorted! Since then I've been using polys and haven't had a problem. Methinks it has something to do with something called ripple current.
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
