[Elecraft] K2/100 - Hi Curr and loss of power control - help! de VK7JB

[VK7JB]

Thanks Don & Mark,

That's what I suspected, but I wondered about U5 & 6 too, whether they may
may have been stung  further down the schematic.  I'll replace the diodes
tomorrow when it's light.  I have a small supply of 1N5711's here in my junk
box.  Then it'll be clear if there's more than just the diodes that've
turned to toast. 

Mark, looking at the dismantling involved to get to the fiddly location of
D16 and 17, I think it'll be just as easy to replace the diodes and be done
with it.  Lifting one end to check would be a good idea though, if they were
in a less awkward location.  

This is an interesting failure.  I wonder if the high voltage you'd expect
on the capacitor of this small loop antenna might have caused this
diode-frying??  I did disconnect the coax from the back of the loop tuner
(de-energised of course) at one stage to connect my antenna analyser to
retune it to another band.  The problem manifest after reconnecting the coax
to the K2.  The SWR was low throughout, but I guess that's not related to
high charge on the variable cap, which would be several kV.    I won't be
using the K2 on this loop antenna again, just in case.  Pity, because it's
great to get a 57 reports working into Austria and Russia and 59 into
Florida, running 50W into a diminutive 1m diameter loop sitting on my picnic
table :)

I'll report on the patient after the surgery...




73,
John
VK7JB



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