[Elecraft] K2 K60XV K1 is not switched on

[gt-i at gmx.net]

Hello,
I recently decided to upgrade my K2 to 60m and ordered the K60XV.
After building and installing the module and all the mods, I could hear 
signals on 60m, but very very weak. Using the XG3 showed a difference of 
8 S-points compared to all other bands. I tried to isolate the problem. 
I checked if the relay K1 would switch at all (removed U1 b4), ok. 
Checked if capacitance changes when turning C1/C2 - looks good. Then I 
installed the module without U1 installed - 60m not recognized any more. 
Seems that U1 is working, basically.
Then I fooled the K2 by installing U1 without pin 11 connected (by 
applying the IC-socket-sandwich trick). And ok, I could now tune 60m 
properly and to the same level as 40m.
So I got stuck now. Is U1 only "half-way" working, that is it does 
communicate on the AuxBus, but cannot drive K1? BTW, I also checked the 
transverter setup to see if relay K2 would be driven - and yes it clicks.
Any ideas welcome!
Thanks/73
Gernot DF5RF