Hi Chris
That is pretty bad luck. I have been operating QRP labs radios without any mods almost constantly since 2018 and never had any issues with finals. One was also working WSPR non stop.
It is very odd why only some folks suffer from blowning finals, given the vast number of sets Hans has sold.
I would be curious to learn about your antenna and PSU. Do you use an ATM?
I really hope you find the cause.
73s Ted
2E0THH
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Ted 2E0THH