Hi Dick, Does your K3S receive OK if the TX Power control is set to less than 12 watts?
Do you have transmitter output if the TX Power control is set to less than 12 watts? If the answer to both of those questions is 'Yes,' then you're looking at one or more of the following issues in the KPA3A 100 watt PA module T/R switch: - failure (shorted) of PIN diodes D5 or D8, OR - loss of DC bias to those diodes, which can arise from a lead break in one of the red toroid RF chokes (L1, L3, L4, L5) OR - failure of bias switch Q6 on the KPA3A board which turns on the bias to D5 and D8 in transmit mode. Even if one or both of the final PA MOSFETs failed shorted, those are isolated from the receive signal path by PIN diodes D5 and D8 being turned 'OFF'. The PIN diodes D2 and D3 are biased 'ON' in receive mode to provide the thru path around the 100 watt PA module. Signal attenuation on receive can be due to problems in the D2/D3 path OR to loading of that path by an unintended connection to the PA module input or output via D5 or D8. I suggest you remove the KPA3A PA module and inspect the red toroids comprising the RF chokes in the T/R switch section. If those are intact and you're comfortable testing the PIN diodes, that will give useful information. Alan, W3DVX has offered repair services on the K3/K3S radios for some years now. You can find him at https://wilcoxengineering.com/. 73, Mike, K8CN ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
