Dave,
You are on the right track - you should have near 8 volts on the anodes
of D2 and D3 during receive. Check RFC2 with an ohmmeter - if it is
open, request a replacement from [email protected]. OTOH, if it shows
a low resistance, check that both leads are properly soldered.
73,
Don W3FPR
On 8/24/2014 2:08 PM, David Doar wrote:
Hi guys. I could use a little help tracking down the cause of a weak receiver
on my newly built K2/10.
All of the test and alignment procedures were satisfactory at each stage of the
build. But unfortunately, when I got on the air, the receiver actually seems
rather deaf. I do hear a few signals, but rarely do they move the S-meter.
After going through the trouble shooting section of the manual with no luck, I decided
to use the N0SS, Tom Hammond (SK) “Cheap ’N Dirty “ signal tracing method to inject a
signal at the suggested test points. I found the headphone volume drops off slightly
when injecting a signal at the junction of D2 & D3, and almost totally disappears
at the junction of D3 &D4. That got me checking the voltages in the T-R switch.
I found that I was only getting about 50mV at the junction of D2 and D3 (anodes). I’m
also getting 0 volts at the cathode ends of D1 and D2. Backtracking from the anodes of
D2 and D3, I get the same 50mV at RFC2. But on the other end of RFC2, I have the
full, supplied 8 volts (receive).
So I’m thinking that RFC2 is defective, and is the cause of the low switching
voltage for the diodes. Does it sound like I’m on the right track?
For reference, here is Tom’s “Cheap ’N Dirty Signal Tracing in the K2” article:
http://www.mmccs.com/mmarc/n0ss/k2_signal_tracing.pdf
Thanks for your help,
Dave
WB4BIN
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