[Amps] How to know when filter caps begin to fail

[Jim Hargrave]

My old Eico model 950 still works great. It goes to 500v and covers most
common electrolytics.

    73s de Jim
       W5IFP


  > -----Original Message-----
  > From: amps-bounces at contesting.com [mailto:amps-bounces at contesting.com]On
  > Behalf Of Carl
  > Sent: Thursday, March 29, 2012 8:28 AM
  > To: Al Kozakiewicz; 'k7fm'; amps at contesting.com
  > Subject: Re: [Amps] How to know when filter caps begin to fail
  >
  >
  > Very few have access to a ESR tester that works at 45V or more
  > and these
  > hand helds are completely useless for this since they use 9V or less.
  >
  > Mine are a military ZM-11 and a Sprague TO-6A plus a 1940 model
  > 16 (Postwar
  > renamed the TO-3) that goes to a bit beyond 1000V and that one
  > has caught
  > several oil filled over the years.
  > Nothing lasts forever.
  >
  > Carl
  > KM1H
  >
  >
  > ----- Original Message -----
  > From: "Al Kozakiewicz" <akozak at hourglass.com>
  > To: "'k7fm'" <k7fm at teleport.com>; <amps at contesting.com>
  > Sent: Wednesday, March 28, 2012 11:42 PM
  > Subject: Re: [Amps] How to know when filter caps begin to fail
  >
  >
  > > ESR is a good indicator for end of service life.  With an
  > ample current
  > > source, increased resistance = more power dissipated in the
  > component =
  > > more heat = more boom.  Increasing ESR is usually accompanied
  > by decreased
  > > capacitance.  If you can't measure ESR, an electrolytic significantly
  > > below the normal -20% tolerance probably means it's
  > approaching the danger
  > > zone in addition to losing effectiveness.
  > >
  > > Although not directly related to the mac daddies used in amplifiers,
  > > apparently there has been a major problem with electrolytics
  > in general
  > > starting the late 1990s, mainly with components labeled as
  > manufactured in
  > > Taiwan (though counterfeits may be a major contributor).  I
  > know that I've
  > > taught the network techs at work how to salvage a large
  > number of dead
  > > monitors without a schematic or any diagnostic tool other
  > than examining
  > > the electrolytic capacitors for bulging.  Replacement almost always
  > > resurrects the device.  There's a wikipedia entry on this
  > problem called
  > > "capacitor plague" or some such.
  > >
  > > Al
  > > AB2ZY
  > >
  > > -----Original Message-----
  > > From: amps-bounces at contesting.com
  > [mailto:amps-bounces at contesting.com] On
  > > Behalf Of k7fm
  > > Sent: Wednesday, March 28, 2012 11:23 PM
  > > To: amps at contesting.com
  > > Subject: Re: [Amps] How to know when filter caps begin to fail
  > >
  > > So, after all the horror stories of exploding caps, I want to
  > mention that
  > > a few months ago, I removed each original capacitor from one
  > of my Alpha
  > > 76A amplifiers.  It was fairly low time and had been sitting
  > on the shelf.
  > > I reformed each capacitor, measured the capacitance, and they
  > were all
  > > within factory specs.  I then formed each one, working up to
  > 450 volts,
  > > the rated voltage.  Each one had very low leakage.  ESR on
  > each one tested
  > > as good as new.  So, I put them back into the Alpha.  I was
  > also surprised
  > > that the original carbon composition resistors were each
  > within tolerance
  > > and quite close to each other.
  > >
  > > I could have installed new capacitors, but after passing all
  > these tests,
  > > I did not hesitate to reinstall them into the amplifier.
  > Heat contributes
  > > greatly to the aging process.
  > >
  > > Unless I was comfortable with the results of these tests, I
  > would have
  > > replaced them.  I own and fly an old wood aircraft.  Things
  > get replaced
  > > if they need replacing - but if they are still good, they do not get
  > > replaced.
  > >
  > > 73,  Colin  K7FM
  > >
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