[Elecraft] K3 no effective TX on 10MHz bands

[Michael Carter]

Hi Andy,

I looked back at your previous posts, but think I overlooked anything that suggested that your K3 receiver is deaf on the 10 MHz band.  Is it deaf on 10 MHz?

If you can inject a signal at 10.125 MHz and hear even a bit of it, that would be useful information.
I'd leave the soldering iron in its holster until you have a better diagnosis.

IF, and that is a big IF, relay K4 is not switching in the additional capacitors for 30M in that bandpass filter section to change the filter center to that band, that would certainly cause relative deafness in the RX.  As Rick, NK7I suggested, pressing or tapping on the relay case of K4 might reveal an intermittent contact, either internal or on the PCB.  Relay K5 is likely working properly if you can hear and transmit on 20 meters - it switches in that 20M/30M bandpass filter, but the selection of K5's contacts is the same for both bands.  The K4 relay itself may be OK, but if the relay coil driver has failed, then the relay may be stuck in the 20 meter position.

Another, more remote, possibility is that the synthesizer is not selecting the appropriate capacitor and coil option for the VCO.  I'd focus on the bandpass filter first, then consider synthesizer issues if you can verify proper bandpass filter selection and continuity at the K4 relay contacts.

73,
Mike, K8CN