[Elecraft] High SWR in to dummyload on 6/10M

[Peter]

Hi

I have a K3 that needs some maintenance.
The SWR on 10 and 6 meters is high (1:2).  On the bands below it is OK 
(1:1).
The ATU had a burnt L  (L10 (IF stage trap)). Both the C and the L have 
been removed and a jumper has been installed.

After reinstalling the ATU, there was hardly any change. The SWR was now 
1:1.9 on 10 and 6 meters.
After this, the ATU was swapped with another ATU from a properly working 
K3.
However, the SWR on 10 and 6 meters remains unchanged and high.

A second test was swap the output pin from ATU to PL259. On ANT 1 the 
SWR remained bad and on ANT 2 it was good.

Then, I directly connected the PL259 on the back to P70 on pins 17-20.
Now the SWR is OK on all bands.

In my view, the cause lies in the control via the P70 pin 1-5 because I 
tested it with 2 ATUs that react the same way.
Does anyone have a tip on how to check its operation?

73 Peter
PC2A