[Elecraft] K2/100 - Won't Turn On

[John Sims]

Fellow Elecrafters--

I've gone and done something to K2/100 #5023.

Symptom:  rig won't turn on.  Heat detected atop heat sink with Samlex 
power supply cable attached.  Hum from power supply after attaching the 
power cable to the K2.  Normal voltage detected at the end of the power 
supply line; 2 volts or so detected when checking the J3 leads inside 
the radio.  Normal continuity between the + and - power supply posts and 
the + and - leads of J3.

Power supply:  Samlex 1223.

This morning XU7ACY was on an 80m power supply birdie and I never worked 
him.  This afternoon when I got home I decided to switch to a regulated 
supply I've used before with this K2.  After attaching the rig to the 
regulated supply it received normally for about 45 minutes while I 
tested an 80m receive loop.  I turned off the rig, went outside to work 
on my transmit antenna, returned inside and tried to turn on the rig -- 
nothing.  While checking to see if all cables were installed properly I 
noticed the KPA100 heat sink was warm.

The only other anomaly recently has been a stiffness in S1, the power 
switch. 

I've tested and cleaned the power pole connectors and all is well there. 

I'm a decent builder but _not_ experienced at troubleshooting.  Any 
ideas where I should start?

Thanks in advance and 73,

John, N7ON