Lightning damage result/repair

[Ron ZL1TW]

Hi
     Yesterday a thunderstorm ran through here, and while I didn't think it
was anywhere too close, the SWR bridge diodes in the KPA100 thought otherwise.
A few hours after the storm, I fired the K2/100 up and it was receiving
fine, but my troubles started when I tried to tune up. I don't recall all
the events, but I do know I was quite surprised when the K2 started to tune
and suddenly all the lights went out. A quick check of the fuse in the
power cord showed the 20amp fuse had blown. Replacing the fuse bought the
set to life again, but when I tried to transmit, the display showed unusual
readings and it was obvious there was no power going up the spout.
Immediate panic set in as I visualized sending to Elecraft for a pair of
new finals. However, after taking the shield off the PA and poking around
with the DMM, I quickly found the FWD diode in the SWR circuit open circuit
and the REV diode gave a reading of 2.2ohms both ways round.
The final out come resulted in a repair that cost me two 98c diodes and a
couple of hours work, as Elecraft cunningly put the SWR bridge diodes in
probably the most awkward place they could think of in the KPA100.
Everything works fine again now, but I have to wonder what else may have
been damaged and just waiting for the likes of Field Day to stop working?
Another mystery to me is why didn't the diodes in the bridge circuit of the
KAT100 go as well?? And what made the 20 amp fuse blow? (perhaps the power
being ramped up too high as the diodes were in their death throws?)
Cheers.......Ron ZL1TW


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[Don Wilhelm-3]

Ron,

Proof positive that lightning can and will do 'strange stuff' one never
knows about its behavior.  It is always a good thing to exercize caution
when the sky 'rumbles'.

I just repaired a K2 (no KPA100) for a fellow that was not connected to an
antenna or powered on when lightning hit nearby and it zapped a PC Board
trace at the DC entry and opened the reverse polarity protective diodes and
zapped his internal battery pack with no other damage apparent.

There is always a chance that other devices were damaged and may fail later,
but short of replacing all the active devices in the K2, there are tradeoffs
to be made considering the cost and trouble vs. the potential for failure
later.  It may be wise to say "If it ain't broke, don't fix it!"

73,
Don W3FPR


> -----Original Message-----

> Hi
>      Yesterday a thunderstorm ran through here, and while I
> didn't think it
> was anywhere too close, the SWR bridge diodes in the KPA100
> thought otherwise.
> A few hours after the storm, I fired the K2/100 up and it was receiving
> fine, but my troubles started when I tried to tune up. I don't recall all
> the events, but I do know I was quite surprised when the K2
> started to tune
> and suddenly all the lights went out. A quick check of the fuse in the
> power cord showed the 20amp fuse had blown. Replacing the fuse bought the
> set to life again, but when I tried to transmit, the display
> showed unusual
> readings and it was obvious there was no power going up the spout.
> Immediate panic set in as I visualized sending to Elecraft for a pair of
> new finals. However, after taking the shield off the PA and poking around
> with the DMM, I quickly found the FWD diode in the SWR circuit
> open circuit
> and the REV diode gave a reading of 2.2ohms both ways round.
> The final out come resulted in a repair that cost me two 98c diodes and a
> couple of hours work, as Elecraft cunningly put the SWR bridge diodes in
> probably the most awkward place they could think of in the KPA100.
> Everything works fine again now, but I have to wonder what else may have
> been damaged and just waiting for the likes of Field Day to stop working?
> Another mystery to me is why didn't the diodes in the bridge
> circuit of the
> KAT100 go as well?? And what made the 20 amp fuse blow? (perhaps
> the power
> being ramped up too high as the diodes were in their death throws?)
> Cheers.......Ron ZL1TW
>

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