[Elecraft] K3 won't power up... ???

[Todd brady]

Hello.....
I was using my K3 this morning and suddenly it just shut off. I thought it may be the power supply ..... so I switched to another one.
when I hook the red/black DC power cord up to power supply .... the power supply won't turn on ...... but if I unhook the power cord, the power supply will work as it should. Both power supplies work fine with my little FT 857D. I checked the fuse on the back of the K3 to see if it had been tripped .... but all seems to be ok. When I turn the power supply on ... it will turn on for a spli second and go right back off. 
Any suggestions on how to get the K3 to power up again ?
Thanks... N4LA / Todd