Bill,
Remove the shield and give it a good visual inspection first - look for
any evidence of overheated components.
Then check the diodes in the T/R switch - preferably with a diode test
function of a DMM, but the ohmmeter will work too - check both the
forward and reverse connections.
Check the 2 small diodes in the wattmeter section (T4 area) while you
have the DMM set to measure diodes.
If you find something awry in the above tests, fix it, but if those
tests/checks reveal nothing, proceed as follows:
If you are not driving a dummy load already, directly connect one to the
KPA100 and try a quick test. If you can get power on without blowing a
fuse, then set the K2 in CW TEST mode and check the PA bias voltage -
you should have 0.6 volts on the base of the PA transistors.
I it is still drawing a great amount of current, temporarily lift one
end of Z1. That will take the 12 volts off the PA transistors and allow
you to see if something other than the PA transistors is causing the
problem.
Tell us what you find and we can go from there.
73,
Don W3FPR
nz0t wrote:
After performing flawlessly for over a year my KPA100 has died for the second
time in about 3 months. I was finishing a nice 20 minute QSO on 10M CW last
week when the rig's lights flickered and the power supply shut down. Now
the power cord fuses blow and there appears to be a short when the power
supply is turned on - even with the rig off. The K2 itself is fine and
works great QRP but I need help with what direction to take with diagnosing
the KPA100 trouble.
May be the KPA100 is upset that my K3 will be here in a couple of months and
it and the K2 will no longer be center stage in the shack?
Any and all help greatly appreciated!
Bill NZ0T
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