I would respectfully suggest that people are jumping to conclusions without logical thinking.
Perhaps if the original poster bothered to read answers, it may help.
I have asked what size PSU he is using, as did another, but no reply.
I asked if it did it on FM, no reply.
It is displaying symptoms of drawing too much current, hence my questions.?
If PSU is too low a capacity, it will cut out. FM being a full current mode, it will cut out. Ignore the FT8, go back to basics and fault find. Put the radio on a dummy load, connected to a known good PSU, and try it again.
You could even check the power lead for dirty fuses or connections, as that is known to cause problems.

Yes, I agree, the power on switches are known as a fault on many radios and would cause this problem. Not that I’ve ever had one fail on me like that. But if there was a problem with that, you would have an idea how it felt and behaved.

Sent from Jeff M0UHF?

On 14 Jan 2023, at 17:50, Doug via <rinsewind79=[email protected]> wrote:

?I've seen that symptom sometimes on the 847's when the power switch is becoming intermittent.
They are a known failure item.

Doug
N7BFS