Capacitor ID help - Printable Version
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Capacitor ID help - ODPILOT - 10-07-2014
I'm not sure if this is a paper cap or a mica cap. It's from a 1954 Philco radio model B 1750. It's shaped like a kidney bean, not like any of the other paper or mica capacitors in the radio. The tip of one side is yellow, then the stripes are:
orange, violet, green, white, white.
The schematic says it is 7.5 pf (mmf) - just want to confirm this is what the capacitor is saying. Thanks
RE: Capacitor ID help - morzh - 10-07-2014
Well, purpe and green are 7 and 5.
Judging by that it is likely 7.5pF.
Now this capacitance is not likely to be paper.
It is either mica or ceramic, given the 50s, likely the former.
RE: Capacitor ID help - Steve Davis - 10-07-2014
I wouldn't change it unless you are sure it is bad.
Steve
RE: Capacitor ID help - morzh - 10-07-2014
Exactly. Micas are fine unless you troubleshoot and find them misbehaving. It is paper and lytics that have to go.
RE: Capacitor ID help - ODPILOT - 10-07-2014
This cap reads 18 pf on my meter -so if it's supposed to be 7.5pf, then I guess it's gotta be replaced. Thanks for everyone's help. [Image: http://philcoradio.com/phorum/images/smilies/icon_angel.gif]
RE: Capacitor ID help - morzh - 10-07-2014
What meter do you have?
before you discard anything, measure your leads' capacitance; it very well might be you are measuring them plus your cap.
RE: Capacitor ID help - ODPILOT - 10-08-2014
Meter is a New Cason XC6013-L. You are EXACTLY right. If I measure the capacitor by putting the probes right next to the capacitor - it reads 7.4 pf - (should be 7.5) but is well within tolerance. Never new that where you put the probes on the leads can make a difference. Live and learn. Thanks,
RE: Capacitor ID help - Joeztech - 10-08-2014
Yes, small value (less than 100pFd) capacitors have to be measured very carefully, often it becomes necessary to remove from circuit and use the shortest leads possible. Any lead capacitace value needs to be zeroed out before measuring the capacitor. That particular cap may be a tubular ceramic that has been dipped in an epoxy coating, then painted. There were a number of low value capacitor types used in that era.
Joe