K2/100 with Total Loss of Sensitivity

[Ray G3XLG]

I've noticed the last few days that the K2 seemed to be only working on a few bands eg 10 metres for the RTTY contet recently was fine but 20 metres seemed totally "dead". Then on Sunday I found 80metres was fine for some CW but 40 metres was dead as well.
Today all bands on the K2 just appear to be noise with very few signals. I tried to tune in the antenna with the KAT100 but couldn't gett any matching on any band. I suspected the antenna or co-ax cable but when I plugged in my K1 to the antenna there was no problem with the internal atu and there were loads of stations on 40, 30, 20 & 18 metres.  So, its definitely the K2 which has a problem.
I'm going to study the troubleshooting section of the manual now but does anyone have any ideas where i should start?
73
Ray, G3XLG

[Ray G3XLG]

My thanks to Geoff LX2AO & Mike K8CN, both of whom replied direct with suggestions to feed the antenna direct to the K2 bypassing the KAT100 & see if there is an improvement.
There was & I found a suspect relay connection. In the meantime I also found I had somehow managed to change the receive antenna setting on two bands in the K2 menu from "Off" to "On"!

Thanks to all
Ray, G3XLG