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@hourglass.com>
To: "'k7fm'" <k7fm@teleport.com>; <amps@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@contesting.com [mailto:amps-bounces@contesting.com] On
> Behalf Of k7fm
> Sent: Wednesday, March 28, 2012 11:23 PM
> To: amps@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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