> Tom,
> Thanks for the reply. On my pasted response from my
> buddy, he states they chose the lowest life (2,000) hours
> caps out of the line. Also, I think the quality has gone
> down since you left Ameritron as they changed to different
> caps from what you mentioned. As far as military over
> rating their caps being foolish, I was recently on a web
> page discussing how many junior engineers are put in
> supply design because it is thought to be simple and it
> also discusses how the Navy talked about how readiness
> could be improved through better power supplies. My
> experience as a 24.5 year electronic tech is that a vast
> majority of problems in fact are power supply related. On
> ships where the engineering load is dropped without
> warning, there is a surge as it is brought back up due to
> surges. This is where the power supply fries. On shore
> (I have loads of experience with mobile comms) we have
> generators that fluctuate. I also have repaired many a
> piece of home electronics that
> have had the varistor fail due to surges at the house line
> power for whatever reason. Over rating capacitors is a
> good thing not a foolish thing. "an ounce of prevention
> is worth a pound of cure" why tempt Mr. Murphy.
Mike,
I'm not posting this to pick at you, but just to show how we
can leap to very wrong conclusions that sound very
authorative.
If people were paying $50K per amplifer and using them with
navy generators I'd probably use the same headroom.
As for your friend changing all the parts, someone should
have suggested checking the resistors right away. By far
most electrolytic problems are caused by bad equalizing
resistors.
They won't blow if there are bad caps. It's nearly
impossible. The caps WILL blow with a single bad resistor,
not the other way around. The resistors are running at about
half the CCS dissipation and are in an airstream. A
capacitor would have to go to 600V just to reach rated
dissipation in that environment, and probably 1200 volts to
fail in a short period. That won't happen, I can assure you.
The caps would be long gone before they took out a resistor.
I certainly can't answer how MFJ does things, but for all
the crying and whining from a few people.....Ameritron
managed to increase sales year after year, often doubling or
tripling every year. When Prime took Ameritron to settle
back debts from DJH, it was selling 5-10 amps a month. Last
I knew it was selling about 150 amplifiers a month.
Had we not slowed the blower and "ticked off" people like
W6WRT, the AL12 series sales would have absolutely died. The
number one complaint was blower noise. It was killing sales.
So we pulled the blower back to the very minimum possible
and still hold seals below rated temperature, and made all
the air go through the tube so we could use the least amount
of air possible.Sales went right up, and "I don't want it"
complaints virtually died.
Most of the things people find fault with are actually
things that would not change reliability in any way to the
typical customer, and many of them actually would have had a
negative impact on sales. Some changes people want actually
decrease reliability.
The only amplifier design influenced by Richard Measures
sold a grand total somewhere around 50-100 amplifiers before
going belly up, and during its life had just as many field
failures from arcing and bad tubes as any other amp using
the same tube brand. As a matter of fact it was tube
failures that killed the only nichrome suppressor amp that
was commercially manufactured.
The 30L1, compared to the 811H a while ago, had a constant
series of factory mods for stability issues. You can still
take most 30L1's, remove the antenna and close the TX relay,
and make a 30L1 into a dandy oscillator. There isn't an
amateur amp out there that does not have some sort of
shortfall because it is a cost driven market.
People should keep all this in mind when they listen to the
backyard Quarterbacks who have never designed and sold
anything into this market. As some of the most vocal experts
what they have done and where they have worked. Have them
point to some product that has sold well up into the
thousands and made a profit in a cost critical market like
this.
BTW, CB amplifiers don't count. Almost anyone can cobble
together a single band 27MHz 4CX5000 or sweep tube amp for
the occasional skip talker. So let's not pretend people get
fired from engineering jobs or companies go bankrupt for
exceeding tube curves in CB amps.
We should all stick to facts and not play silly games about
how much better any one of us is than the rest of us. There
isn't anything or anyone that is perfect.
Now let's all play nice and we can learn something FACTUAL
for a change.
73 Tom
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