[Elecraft] Help with defective KFL3A-400 needed

[Marcus Busch [DL1EKC]]

Hello everybody,

I have a friend's KFL3A-400 on my bench which shows a 20 dB passband attenuation with 
high ripple. The fault was originally detected by a 3 S units signal drop in the K3 
compared to its other crystal filters. The filter was working perfectly until 
recently.

I disassembled and measured all crystals and they seem to be OK, with the exception 
of crystal no. 6 showing a higher ESR. But is this an issue?

The input and output transfomers seem to be OK as well, although checked only for DC 
conductance and isolation. All solder joints have been checked.

These are my measurement results:

passband: http://www.dl1ekc.de/LinkedContent/DL3QQ_KFL3A-400.png
crystals: http://www.dl1ekc.de/LinkedContent/DL3QQ_KFL3A-400_Quarze.pdf

Any filter expert around here who can point me into the right direction? Any help is 
greatly appreciated.

VY 73

Marcus