Another similar problem with IC-7800, sn 0201781, mfg in 2007, sold March 2011 (new at old price).
Operation for 2 hours on 18MHz, one hour CW and one hr. SSB using 200watts into 2:1 or less antenna.
No problems and working great.
Immediately went to CW to test SWR on 24, then on 10.1, ALL OK AT 200 WATTS AND KEY DOWN 1.5 MINUTES EACH BAND, and then on 7.0-7.2.
On low end of 40meters, with key down at 200 watts (30 seconds) the rig shut down completely with the POWER switch going blank; radio totally dead. Switched off the rear AC switch, waited 30 sec and switched rear switch back on and the radio came back on to receive immediately with green ON POWER light on.
Changed RF POWER knob to full CCW (lowest power), listened to 40meter signals are ok. Key down and radio turned off completely, again.
Now, rear AC ON POWER switch on, but no function on the front switch ON POWER, no orange light, and
no green light and negative function on all.
Dead at $10,000 (or more).