[Amps] Ameritron Amps

[mike kendall]

OK,
    My buddy, Don, has answered back to me about his AL-1200 problems and it really "says it all".  Like I said before, if you are an appliciance operator you should be able to count on the factory being able to fix things for you.  Here is a cut and paste from his email that also talks about how good another company is. You get what you pay for:
Your fiend with two AL-1200's and an AL-1500 probably has amps that were 
  built prior to MFJ buying Ameritron.  My problem with the AL-1200 was all with the 
  filter caps in the power supply.
      They are just plain under-designed.  There are eight 450V caps in the supply.
  With a no-load plate voltage of 3600V that gives a 0% margin.  For miltiary 
  equipment we typically design anywhere between 40% and 60% margin.  
  When I pointed that out the Ameritron service rep his response was that 
  "Well the loaded voltage goes down to 3300V so there's plenty of margin",
  which is bull&*%$.  In intermittent amateur service the typical duty cycle is 40%
  so the caps are seeing 3600V more often than not.  The caps began to arc
  internally, and then blow the balancing (bleeder) resistors.  The supply blew
  four times.  And one of the big selling points on their advertizing is their
  bullet-proof power supply design - RIGHT!  They currently use the same
  design in the AL-1200 and the AL-1500.
      In addition to that, they are listed by CDE as 2000 hour MBTF caps.  At an
  hour and a half of use a day - three years and they're done.  CDE has 
  500V and 550V caps in the same value at up to 5000 hour MTBF.  The 
  cost of using those would have been peanuts compared to the total cost of the 
  amplifier and would have made a much more robust design.
      Since the last time I got it fixed it's been behaving fairly normally.  But last
  year I bought an Alpha-78 that I just love.  I also just found a set of three spare
  8874's for it for $400.  Not knowing how many hours were on the spares, I'm
  currently running the spares and I'll let them go first.  They're a little softer than
  the ones I got with the amp - the spare gets about 1400W out with 100W drive.
  The tubes I got with the amp get at least 1650W with full drive, but the difference
  isn't that big a deal. 
  73,
  Mike who also owns an Ameritron
  

Gudguyham at aol.com wrote:
        In a message dated 7/29/2006 2:46:36 A.M. Eastern Standard Time, ke6cvh at yahoo.com writes:
  don't want to bash Ameritron but I have a friend who bought an AL-1200 and did have considerable problems with the electrolytic capacitor bank on the HV power supply.  They did not have a good safety margin on their ratings when compared to the output voltage.  My friend recommended a good US source for an electrolytic that would allow a safety margin.  I seem to remember he blew out the caps a couple of times before he got rid of it.  A great looking amp with a problem that needed to be fixed and Amertron unwilling to fix it properly.  I own an ALS-600 solid state linear and have experienced problems with the open frame relay.  I read on Eham.net that others have also had this problem.  I am currently looking into replacing it with a Gigavac device but once again, think Ameritron should either offer a QSK vacuum relay as an option, standard, or some other type of fix.  I have had two Ameritron linears, the AL-80A was OK (also blew a HV electrolytic but plenty of space to
fix it easy).  Overall, my opinion is Ameritron  is good but they need to listen to their customers a little better and fix problems a little quicker.
  73,
  Mike

  
  Probably using the GREEN lead on the transformer which offers HV at 4KV.  It is only for those who have low line voltage.  I'll bet that was the problem. Lou


 			
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