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@aol.com wrote:
In a message dated 7/29/2006 2:46:36 A.M. Eastern Standard Time,
ke6cvh@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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