[Elecraft] Different max power on different bands

[Robert Hayes]

 Hi Keith, 
I don't think so.  Everything worked fine during the NA SSB Sprint on Saturday evening and I was using the amplifier.  Then when I went to use it Monday I noticed the power output was lower.
But based on what I am seeing it does appear to be the LPA.  If it was an issue with some sort of RF Energy Kickback and I was using the amplifier with the output set to 100 watts, would it really damage the LPA and not the HPA?  Regardless, I will either need to swap out the LPA itself or replace the transistors in the LPA I have here, which I am happy to do.  Is the transistor different from the ones used on the K3 LPA?  Since I have some K3's here I could grab one out of them in the short-term.
Any other ideas or suggestions for repair?
73 Bob KW8N
    On Thursday, March 27, 2025 at 01:33:53 PM EDT, Keith Trinity WE6R <keith at elecraft.com> wrote:   

 Hi Bob;
Did you have an "event" with an external amplifier? Like transmitting 
with no load causing an oscillation and "kick-back" of RF energy back to 
the K4.
I see you confirmed the LPA is damaged and posted on the groups.io forum.
Keith WE6R K3/K4 Tech