[Kenwood] no Tx on my 940

[Marc Bruvry]

Hello group:
My TS-940SAT has been trouble free (until now, despite the "troubles" we 
are burdened with) and all of a sudden it is ceasing to transmit after a 
few minutes on the air???
It starts out fine and then there's nothing.  I noticed however that it 
still will transmit CW, and my SM-220 shows a carrier when I try SSB, 
but no modulation???  After I shut it down for a few hours, everything 
seems to work again - for a few minutes...
Any ideas?
Thanks, Marc / KF6VNT