Audio Systems: Kenwood ampllifier flashes p-off, sansui amplifier, circuit resets

Question
I have an old Kenwood stereo system model KA- 791.
The display on the amplifier shows normal for a few seconds, and then swiches to a message that blinks "p-off". I disconnected ALL cables  and turned it off and on again , and still, the same message.
I assummed that if the transistors were damaged, it would have blown a fuse.  
Do you have any suggestions on how to troubleshoot this problem?

Answer
Dear Carla,

What does the manual say?

I can't find one on line, so I'll guess that you've tripped the thermal protection ("p") circuits. Generally, this kind of circuit resets itself once the event which tripped it has passed. However, with older units (I have an old Sansui amplifier that's cranky like this), sometimes they can't. I recommend taking the unit into a qualified repair service to reset the circuits and for a general check-up: something tripped the circuits in the first place.

Good luck. And thanks for choosing allexperts.com!

Kindest regards,

Kevin