Topband: .TX Mica Caps

[Rob Atkinson]

My opinion:  the PCB scare is overblown, just like lead in paint,
asbestos, etc.  If you are intelligent about it, taking prudent
precautions, PCB in caps and dummy loads should be fine.  I'm sure
hand wringers will weigh in with all kinds of nanny state far fetched
what ifs, but I have PCBs around here and I'm fine.

>-It catches on fire and fills the transformer vault with thick smoke when the
>monster transformer melts down?

At a ham station?

>-When a few drops leak out of a filter capacitor in one of our radios or
>transmitters?

Mop up with a paper towel and drive on.

>-If an electrician working on very big transformers puts his arm down in the
>oil to make connections and does it for some years?

I've heard of guys exposed that way and they were fine but again, that
doesn't sound like a likely ham radio scenario.

>-If I have a dozen 1000 and 2000 volt oil capacitors in a box in my barn?

Usually these caps use a paper dielectric impregnated with pcb oil.
What happens over time is that the seals around the lugs dry out and
there's a gradual ingress of air which compromises the dielectric and
the cap shorts out.  Store them upside down or better yet, do a
leakage test (methods for this can be found using google), use or sell
the good ones and properly dispose of the leaky ones.

>-If my want list has the RCA AR-88 on it which has oil filter caps?

That set has a one-can three section filter cap bank made of of three
500 v. 4 mfd paper dielectric oil caps.  In the transmit position on
the front panel ("Trans") the high B+ can hit 480 v. with no load on
it.  That will usually cause those old oil caps to fail.  The best fix
is to buy 15 or 18 1 mfd 600 v. polypropylene axial leaded caps and
make three clusters of 5 or 6 each and replace each can section with a
paralleled cluster.  Remove the stock cap unit or leave in place for
looks.  The new caps will fit underneath.  They will not leak and
they'll out last us all.

73
Rob
K5UJ