Paul, The diodes are the most likely suspect, so replace them first and re-check.
You are correct that the problem is that the wattmeter is not feeding the power back to the MCU and the power becomes uncontrolled.
Wattmeter damage is normally a result of static coming in on the antenna feedline. If you do not have an means of disconnecting the antenna when not in use, it would be wise to add that - switching the K3 to a dummy load would be a good addition too.
73, Don W3FPR On 1/21/2018 1:39 PM, Paul Christensen wrote:
Dick & Don, Thanks for confirming. Although unlikely to be the source of trouble, It also appears U6 and U8 are in the VFWD and VREF circuit paths. I'll order up everything and have it on hand when I replace this week. It could also be a passive problem like a marginally-corroded connector, or failed resistor. By the way, the problem manifests with high SWR and power set readings that no longer match anything close to actual output power into known good loads. The SWR reading fluctuates excessively with change in the PWR control and slight changes in the control quickly lead to 120W power spikes when the K3 display indicates 15-20W. This tells me the ALC circuit is not getting a good forward power sample. So, it appears the SWR bridge or surrounding circuitry has partially failed.
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