[Elecraft] KPA100 U6 voltage issue

[Catherine James]

I recently began building a just-purchased KPA100 kit for my K2 #5191.  All was well until I reached the voltage checkpoints on page 26.

U5 pin 1 is 0.8 volts (not 0 to 0.1)

U5 pin 7 is 0.9 V (not 0 to 0.1)

U6 pin 6 is 17 volts (not 0 to 0.5)


I am much more concerned about U6, but perhaps the U5 voltages give you more information.


The no pa pa message comes up as expected, and the current indicated on the k2 display is less than 400 ma.


The keys are in the correct places on the ribbon cable. Nothing has ever been plugged into the DB9 port, so this is not the issue where a standard serial cable damages the kpa100 through the aux port non-standard wiring.


The K2 appears to work fine with the partially built KPA100 disconnected. Voltages on D9 of the K2 RF board (my proxy for V RFDET) are much lower than 17 volts (kpa100 not connected) so the high voltage appears to come from the KPA100, not the K2.


I have the KSB2 installed, but haven't explored that its voltages, and haven't tested whether it still works following the "17 volt incident".


I don't see any obvious solder bridges on the KPA100.


Where would voltages near 17 volts normally be found on the KPA100 board?


Thoughts on next steps?


Cathy

N5WVR

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