Fw: [Boatanchors] rotor starting capacitor

[Mark Foltarz]

Brian,

  Yes,if you apply a reverse DC supply to an electrolytic you will over time
dissolve the aluminum oxide crystal layer that is the dielectric. With this
layer gone the cap esentially shorts out.
 
 However, the "trick" of putting two polarized caps back to back and applying
an AC voltage seems to yield good results and also exhibit a  remarkarbly long
life. It is my belief that the Al oxide layer influenced by an alternating
voltage does not degrade in a similar fashion as with a  reverse DC voltage.

 I don't have the compressor any longer, but a starting capacitor was cobbled
up like Peter's arrangement and worked without the predicted ( and expected)
Boom. It ran for several months before the tank was condemmned.

  And the idea of using the back to back elecrolytics for rotor boxes has been
circulating for years.

 Sometimes any port in a storm is a good port. I imagine it just depends on the
circumstnces.

  de KA4JVY

  Mark

 

--- Brian Clarke <brianclarke01 at optusnet.com.au> wrote:
> 
> Sorry, Peter,
> If you wanted a non-polarised or ac rated capacitor, wiring two polarised
> capacitors back-to-back is NOT the same a non-polarised or ac rated
> capacitor.
> What you have done is increase the risk of depolarising BOTH capacitors,
> with
> attendant consequences.
> 73 de Brian, VK2GCE.
> 
> You said:
> I use the real cheap and lazy way to replace these caps. Either rummage
> the junk box for two "regular" electrolytics at double the capacitance or
> pillage them from discarded computer or monitor power supplies and just
> wire them back to back. PC mounted or wire leads makes no difference as
> long as I can get to the leads. No one looks inside my rotor box but me.
> This has always worked for me in all the CDE/CDR rotors I used over the
> years including the CDR TR-4, which I bought in 59, and still turns a TV
> and FM antenna.
> 
> On Tue, 6 Jul 2004 19:15:11 -0700 (PDT) Glen Zook <gzook at yahoo.com>
> writes:
> > As a result of my recent need for a control box for my
> > 45 year old CDE AR-22 (hopefully have one on its way)
> > I discovered a very inexpensive source of a
> > replacement for the starting capacitor that is used in
> > most brands of rotors.
> >
> > The cheapest place that I found these was W. W.
> > Grainger Company.  They have branches in many areas of
> > the country.  However, they no longer sell to
> > individuals.  But, if you have a company, or work for
> > a company and have a business card, they will open you
> > a "cash" account and you are in business.  Also,
> > Grainger has all sorts of other things that you just
> > "can't live without"!
> >
> > Anyway, Grainger part number 4X064 is a 110/125 VAC,
> > 50/60 Hz, 233-280 mfd capacitor that works perfectly
> > in place of the same range in capacitance but 50 VAC
> > capacitor that is used in most rotors.  The price is
> > $4.07 in single quantities.  The capacitor is made by
> > Mallory and their part number is 3534B2A0233A110.
> >
> > I would suspect that the capacitor is available from
> > motor rebuilding shops, etc. under the Mallory part
> > number.  However, the price may be a little bit
> > higher.
> >
> > Since the capacitor is rated at 110/125 VAC they are
> > slightly larger than the original capacitors.  But,
> > they will fit in most control boxes.  Also, they had
> > terminals for "slip on" connectors.  But, I had no
> > problem soldering on wires to make the connections
> > inside the rotor control boxes.
> >
> > Since I was quoted prices up to about $15 for a
> > replacement capacitor, I definitely could solder a
> > couple of short wires to the capacitor and save well
> > over $10!
> >
> > Grainger's web site is
> >
> > http://www.grainger.com/Grainger/wwg/start.shtml
> >
> > and the description of the capacitor can be found by
> > using the "search" function at the top of the page.
> > Just "click" on the arrow next to "keyword(s)", click
> > on "Grainger item number", and then put in 4X064 in
> > the box to the right and click "go".  It will take you
> > right to the item!
> >
> > Anyway, if you are a firm believer in the principles
> > of the conservation of your finances and labor (you
> > can read "cheap and lazy") like me, and if you are in
> > need of a starting capacitor to repair your rotor (the
> > capacitor going bad represents at least 90% of the
> > problems with rotors), then this capacitor is a viable
> > alternative to paying what the rotor manufacturers
> > want!
> >
> > Glen, K9STH
> 
> _______________________________________________
> Boatanchors mailing list
> Boatanchors at mailman.qth.net
> http://mailman.qth.net/mailman/listinfo/boatanchors
> ** List Administrator - Duane Fischer, W8DBF/W9WZE **   
> ** For Assistance: dfischer at usol.com **         
> $$ For vintage radio info, see the HCI web site $$      
> http://www.w9wze.org    
> 
> 


__________________________________________________
Do You Yahoo!?
Tired of spam?  Yahoo! Mail has the best spam protection around 
http://mail.yahoo.com