[ARC5] Use of a Variac

[Tom Lee]

I'm fairly certain that those were not electrolytic capacitors. Just 
plain old nonpolar caps. Oil is a lousy electrolyte, but a good 
insulator. Your description matches that of high-voltage, uF-level caps 
of the WWII era. Heathkit used some war surplus oil-filled caps in their 
first scopes, for example.

--Tom

-- 
Prof. Thomas H. Lee
Allen Ctr., Rm. 205
350 Jane Stanford Way
Stanford University
Stanford, CA 94305-4070
http://www-smirc.stanford.edu

On 4/23/2020 18:33, J Mcvey via ARC5 wrote:
> The ones I'm thinking about are usually bolted to the chassis , not 
> the tab type. Very old
>
> On Thursday, April 23, 2020, 8:42:01 PM EDT, Richard Knoppow 
> <1oldlens1 at ix.netcom.com> wrote:
>
>
>    Oil filled electrolytics are new to me. Are you sure this was
> not a paper cap? There are both wet and dry electrolytics. The
> very early ones were wet, that is, they had liquid electrolyte.
> They were position sensitive. Then so called dry electrolytics
> were developed. In these the electrolyte is a paste.
>    The oil filled caps I know about are paper or sometimes
> plastic dielectric. The oil is used as both a sealant against
> moisture and sometimes to increase the dielectric constant. I
> have seen plenty of WW-2 vintage bathtub oil filled paper caps
> where the seals disintegrated letting the oil out. A mess.
>    I may be wrong but I think electrolytic caps need to be
> ventilated, which oil filling would make impossible.
>
> On 4/23/2020 4:42 PM, J Mcvey via ARC5 wrote:
> >
> > The only ancient electrolytic caps that I ever ventured to save
> > is the oil type. Sometimes the seal can be repaired and
> > refilled..  The dry type just get changed.
> >
> > When bringing up a radio in unknown condition, I check for
> > obvious short issues with a DMM before applying power.
> > I use a 60 watt incandescent light bulb in  series with the
> > line. This does a pretty good job of current limiting and is a
> > visual indicator of the current being drawn. After the initial
> > current drawn by the caps charging, the bulb should be dim. If
> > the bulb stays bright , there are issues. if the bulb is bright
> > at moment the switch flipped on , in a tube set, the
> > transformer may be bad or has a short in or across a winding.
> >
> > I don't have the patience to try reforming caps that may or may
> > not respond to treatment.
> > On Thursday, April 23, 2020, 7:25:40 PM EDT, Mike Feher
> > <n4fs at eozinc.com <mailto:n4fs at eozinc.com>> wrote:
> >
>
> -- 
> Richard Knoppow
> 1oldlens1 at ix.netcom.com <mailto:1oldlens1 at ix.netcom.com>
> WB6KBL
>
>
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