[AMRadio] Capacitators needed

[bcarling at cfl.rr.com]

Bill & Gary,

Don't try telling my old VALIANT that about the dividing resistors not 
being necessary!

I had one Valiant that I used for a few years. When I first got it I put 
it on the air up in the DC area, and I noticed after a while it would 
make this LOUD bang every few minutes.

It seemed to depend on how much plate current I was running. 
Several things threw me off the scent till I finally figured out that one 
of the "balancing resistors" across the series elecvtrolytics, had 
come disconnected. So the cap would charge up until it hit almost 
double it's rated voltage and then: POW!

By the way these resistors also serve as safety bleeders, so don't 
pay too much heed to the Mallory engineer unless you want either 
arcing electrolytics or charged caps with the juice off. Yes you 
could possibly do without them for balancing purposes,
but even if one capacitor gets excess voltage for a few seconds 
while things are first charging up, I can't imagine that being too 
good for it!

I bought new (smaller) electrolytics for that Valiant BTW - just to be 
on the safe side after all that arcing!


On 24 Feb 2002, at 23:07, Gary Schafer wrote:

> Hi Bill,
> 
> Checked ebay and didn't see anything yet. Saw a couple of oil caps though.
> 
> I hadn't heard that it was ok not to use equalizing resistors with a string of
> electrolytic caps ?
> 
> Not using resistors or caps across diodes I know is ok to do. With the newer
> diodes  they all now have an avalanche area that they conduct at with reverse
> current so they equalize themselves. From what I understand they have been
> made this way for about the last 15 or 20 years.
> 
> 73
> Gary  K4FMX
> 
> 
> 
> wwd at netheaven.com wrote:
> 
> > Search on eBay. Electrolytics are offered everyday. Mostly in one of those
> > huge catchall electronics/testgear categories. I still see 1992 Michicon
> > lots. Same as the stash I have here- it was a good year.   :)
> >
> > BTW, just hook the new caps up in series by themselves. Forget that
> > nonsense about the "dividing resistors". These, when connected across each
> > electrolytic, act contrary to the normal "failure-mode" of electrolytics
> > so their use is non-sensical. This from a Mallory engineer, not me.
> >
> > Same goes for "dividing resistors" across each diode in a s/s string, but
> > that is another troll.
> >
> > Test by bringing up each cap individually to its working voltage. No need
> > to tarry-  do it in no more than ten seconds. Let it (them) cook for an
> > hour or more to get a good etching going, or whatever it is they do.
> >
> > Good luck,
> > Bill
> >
> > --
> > -----------------------------------------------------------
> > wwd at netheaven.com           N2KQA
> > --------------------------------------------------------
> >
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