My LK 500 ZA gets very hot when operated for any length of
time. I do not think that the stock fan is adequate for the
job. I am planning on adding at least one fan externally to
pull out some of the hot air from the 3-500Z's. >>
Pulling air out is a bad idea. Fans do a terrible job of
sucking air. Think of them as pressure amplifiers.
If you pressurize the inlet of a fan or blower, it greatly
increases outlet pressure. If you draw on the outlet it
hardly changes airflow. The inlet fan largely sets the
volume of air. The same is true for restrictions. If you
restrict an inlet, there is a huge air volume change. If you
restrict and outlet the same amount, there is much less
Has anyone else had this problem? With the amount of heat
generated I am sure that some other components inside that
box are stressed from the extreme heat. I just want to
alleviate this condition before other parts start to fail.>>
The priority of the owner of Amp Supply was always noise.
It is understandable why, since noise generates many more
complaints than heat.
I'm sure that the bandswitch problems associated with this
linear are a direct result of the heat retained within the
Not a chance.
Catastrophic instant bandswitch failures are the result of
excessive voltage. Excessive voltage is almost always caused
by an antenna system arc or failure or improper loading for
the drive power applied. Poor relay sequencing is another
Many bandswitches (by all manufacturers) are rated very
close to the failure voltage to minimize cost, and they
assume people run the amplifier correctly. Amp Supply also
had a history of not using the best contact arrangements in
Long term gradual failures that do NOT involve arcs are
caused by excessive current. They are usually associated
with RTTY operation or heavy duty cycle modes especially on
Parasitics are very rarely the cause of a failure in a
bandswitch. Measurements can prove that. That's the fantasy
of one California Ham.that has some people fooled.
If I wanted to improve bandswitch life, I'd be sure the
amplifier was loaded heavily enough and everything in the
antenna system was top shape, and that the switch itself was
wired the best way possible without sharp points in the
connections. Also make sure it is not a make before break or
"shorting" switch. Amp Supply had a history of using
shorting switches, but what they really should have been
using was a non-shorting switch with pick-up and hold
You do want to short all the unused taps on lower bands, but
that is called pick up and hold or progressively shorting.
What they ordered was generally a shorting type switch,
which has significantly lower contact to contact voltage
rating. Sometimes you can bump the alignment of a shorting
switch wafer and turn it into a non-shorting wafer.
I think many people assume the switch is misaligned when it
actually was the wrong type of switch. By cranking the wafer
alignment to the end, you can make it look like a
non-shorting. But it was really the wrong part.
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