Feeding 20 Volt to a K3, not good!

Fried D12 in K3

Here is a short update on my fried K3.

The drama happened in the last hour before CQ WPX SSB when we where about to kick off a Multi Operator Single station effort from SE0X. Patrik SM0MLZ was practice running on 40 meter when I noticed the the shack lights flickering. When Patrik keyed, the 12 volt shack lights lit up with dual intensity for a fraction of a second. I immediately pulled power and we measured the PSU which now delivered 20 volt.

After replacing the PSU with a new one, the K3 never came back to to life and we were forced to run the whole contest without a multiplier radio. (Always bring a backup).

When returning home I contacted Elecraft support and got instructions from Gary AB7MY to check two over voltage protection diodes. D28 located on the main board and D12 on the KPA3 amplifier board. The photo shows how D12 on the amplifier board being almost unsoldered by the heat emitted from the diode when shorting. Both diodes where replaced and the K3 came back to life again.

The radio is now back in service and performed great in CQ WPX CW. Thanks to Elecraft for great support!