Hi to the group and Gary at Elecraft,
A week or so ago I queried this group about a problem with no SSB audio when
transmitting. Several people offered helpful information. I've also
corresponded with Gary three or four times. The problem has been solved.
Note I said solved not completely corrected. More about that in a moment.
My thanks to everyone who helped and especially to Gary for his patience and
useful guidance.
As it were, there were two audio problems making this one a particular
difficult nut to crack. Initially the U3 stage was dead. Putting audio on
U3-4 from any number of sources produced no audio out of the stage and some
of the DC voltages on the IC were grossly beyond tolerance. After extensive
troubleshooting and replacing U2,3 & 4 on the KSB2 with no progress I
replaced C31 and C14. Once removed the capacitance of C31 checked okay at
2.2 uf.....eliminating shorts and opens. However, upon removal of C14 the
negative lead had about a quarter inch play inside the cap. So apparently
it was open. But, still no audio out with the microphone. However, when
injecting audio from my computer at microphone level into U3-4 I now had
transmitted audio. That was a nice sound for a change. Thru a coupling
capacitor I injected audio thru pin one of the microphone connector and
audio was again transmitted. So the Elecraft/Heil MD2 microphone is
apparently defective. The coupling capacitor was used because of the bias
voltage on the "AF" line to power the preamp in the MD2. (In broadcasting
we called that "phantom" power......didn't like it then and have more reason
to not like it now.)
So at this point I am looking for suggestions for a suitable microphone that
has the correct output level and does not need the bias (phantom) voltage.
If you have suggestions I would sure appreciate it. I'd like to get this
going in time for Field Day. I'm thinking about gutting the MD2 and putting
the parts of an old Radio Shack microphone in it. I'll have to make sure
the RS microphone element will work with the K2. It doesn't need phantom
power so I'll take out the resistor.
Again, my thanks to everyone who patiently offered their help and especially
Gary. Have a good day.
Jim, AB0UK
K2/100 s/n 4787
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