[Elecraft] KXV3 Issues - endless frustration

[Udo Langenohl - DK5YA]

Just got my KXV3-B as a replacement of the former KXV3-A. Installing 
complete after 1 hour. Removing the back panel makes things much easier 
btw. But there's an issue. The 1 mW calibration fails. Thats what the 
Elecraft Utility says:

Elecraft K3 Utility Revision 1.13.5.9
OS Version 6.1 Build 7601 Windows 7/Windows Server 2008 R2
K3 MCU revision 05.26. RS-232 speed 38400 bit/s.
Starting 1 milliwatt calibration
Calibrating at 1.900 MHz
Calibration power settled at " 1.800.00;"
Elapsed time: 5 seconds
Tx Gain calibration failed because transmit power did not reach the 
expected value
1 milliwatt calibration failed

Wait, there's more to come. I made a replacement because my guess was: 
KXV3-A has a damage.
I use my K3 mostly on VHF with transverters, especially on 144 MHz EME. 
I'm running a Xpol configuration with 4 antennas on 144 EME with two 
identical transverters, both in phase and locked by a common external LO 
with 10 MHz GPS control for Hpol and Vpol.
HPol RX is fed to the KXV3 XVTR In/Out while Vpol is fed to the AUX RF 
input. I can listen to both planes simultaneously using diversity receive.
But something very strange happens when I compare signals on both 
planes. I have a 144 MHz beacon nearby (just 25 miles away). That beacon 
is running 8 W on a Hpol antenna. On my Hpol (main RX via KXV3) input 
this beacon comes up to S9+35 dB while on Vpol (second RX via AUX) it's 
endstop (S9 +60dB). The beacon is in the line of sight, there's a lot of 
RF on my location from this beacon.
It's definetely not from the transverters or from mismatched antennas 
because when I change inputs and connect the Hpol transverter output to 
the AUX RF it's suddenly S9 +60 dB too. Both main and sub RX are exactly 
in the same configuration, filters, bandwidth, NB Off, etc..
I checked S/N on KXVR3-A (old board) and AUX few days ago with my 
HP8664A signal generator.
On 28.200 (TVTR IF) I measured:
Top values:
KXV3-A TVTR IN:       -10dBm = S9+25dB
AUX IN:             -10dBm = S9+60dB (!)
KXV3-A TVTR IN:          +3dBm = S9+60dB
Huge difference of at least 13dBm
Low values:
KXV3-A TVTR IN:      -134dBm = signal detectable
KXV3-A TVTR IN:         -140dBm = none
AUX IN:                -140dBm = clear signal detectable
Again a difference of at least 6dB or even more.

Now, with the new KXV3-B it's even worse, at least 22 dB difference 
between the AUX IN and TVTR IN.

What the heck is going wrong here? MAIN RX dead?

73 Udo, DK5YA

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