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

[Carl]

They have also received transformers with more than normal HV Gerald. I dont know how many got out to customers but they were for the 3 big amps.

The Amp Supply 3-500 amps also get on the edge with a high AC line since they use only 7 caps.

Carl
KM1H





  ----- Original Message ----- 
  From: TexasRF at aol.com 
  To: km1h at jeremy.mv.com ; gene-may at hotmail.com ; amps at contesting.com 
  Sent: Wednesday, March 28, 2012 10:12 PM
  Subject: Re: [Amps] How to know when filter caps begin to fail


  Hi Carl, as you know, there are only eight of those filter C's in the Ameritron amps. When AC line voltage gets up around 245vac or so, the unloaded plate voltage gets close to 3600vdc. That leaves very little or no headroom with a string of 450v caps, let alone ones that top out at 440v.

  I learned all about this the hard way when an AL1500 was strapped for 200vac operation in an attempt to get more power output.

  Not a pretty sight! Dumb! Dumb! Dumb!

  73,
  Gerald K5GW





  In a message dated 3/28/2012 8:12:58 P.M. Central Daylight Time, km1h at jeremy.mv.com writes:
    After a short time reforming of modern caps anything over 1ma at 450V I 
    consider junk.
    Ive also rejected new caps that started acting up at around 440V which 
    caused Ameritron grief when I told them. They found out their supplier was 
    short changing them on the aluminum and have been testing....and rejecting 
    since.

    I buy large amounts of repair parts from them so they listen when I report a 
    problem.

    Carl
    KM1H



    ----- Original Message ----- 
    From: "Gene May" <gene-may at hotmail.com>
    To: "Amplifier Mailing List" <amps at contesting.com>
    Sent: Wednesday, March 28, 2012 8:19 PM
    Subject: Re: [Amps] How to know when filter caps begin to fail


    >
    >
    > 1.  I, too, have shared Bob K6UJ's experience with an electrolytic cap 
    > exploding, and the mess was awful enough to make me conservative about the 
    > issue of replacement.  The goo between the foil seems to be somewhat 
    > corrosive, was slow to clean off, and  damaged some of the metal it got 
    > on.
    >
    > 2.  I'm cheap, and have used many surplus electrolytic caps.  Along with 
    > Glen K9STH's suggestions, I suggest that anyone also using surplus caps 
    > connect them in series and place some DC across for a few hours, then see 
    > how much they leak.  I toss anything that gives off any more than a few 
    > watts -- I've seen leakages of 20 - 30 mA at voltages of around 300V (6 - 
    > 9 watts) on surplus caps -- and know others who are even more conservative 
    > than I about throwing them out.  They can be so much cheaper than new that 
    > I think it is cheap insurance being conservative.  Along with Glen, I have 
    > found that frequent usage tends to make electrolytic caps last longer, not 
    > go bad faster.
    >
    > 3.  Finally, particularly if you use surplus caps, I suggest that AFTER 
    > THE CAPS ARE THOROUGHLY DISCHARGED, every so often it is worthwhile to 
    > simply feel them after they have been under power for a few hours, and 
    > replace the whole batch if any one of them is particularly warm.
    >
    > Gene May
    > WB8WKU
    >
    > _______________________________________________
    > Amps mailing list
    > Amps at contesting.com
    > http://lists.contesting.com/mailman/listinfo/amps
    >
    >
    > -----
    > No virus found in this message.
    > Checked by AVG - www.avg.com
    > Version: 10.0.1424 / Virus Database: 2113/4900 - Release Date: 03/28/12
    > 

    _______________________________________________
    Amps mailing list
    Amps at contesting.com
    http://lists.contesting.com/mailman/listinfo/amps


------------------------------------------------------------------------------

  No virus found in this message.
  Checked by AVG - www.avg.com
  Version: 10.0.1424 / Virus Database: 2113/4900 - Release Date: 03/28/12