[Elecraft] K2 PA runaway current

[Damon Wascom]

Hello elecraft list,

     I need some help with troubleshooting my K2. I destroyed my finals (twice) due to a shorted cap (C4) in the KAT2. For troubleshooting purposes, the finals have been temporarily replaced with 2SC2078's ($0.68 vs. $6-11 for the 2SC1969's). My problem is when I TX at any band and any power setting the current starts to build until I get a Hi Cur warning. 

     At this point i've: re-worked ALL solder joints on the RF board, performed signal tracing per the manual, inspected every component visually, checked the resistors and semiconductors in the TR switch and PA with my DMM (power off and voltages during TX) and pulled out my remaining hair. 

     The same problem happens with the 2SC1969's in place so the substitution of the finals has been ruled out. I just don't want to fry any more (I can't tell my XYL oops, I did it again...)
She is already upset with me about this. 

     Here is my K2 configuration:
K2 #: 06351 (15W), KNB2, KSB2, KAT2, KAF2, KIO2, K160RX, K60XV and KBT2.
In other words, "Fully Loaded". 

     I have been conducting tests with my MFJ-969's dummy load. My belief is that the problem is in the PA but that's just a guess. 

Thanks, Damon KC5CQW


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