Ppower on then standby problem Kenwood KR-...

This fault may be similar to a Harmon Kardon AVR1550 fault I recently encountered. I did all the usual checks e.g. testing for presence of DC on speaker outputs etc. but all seemed fine, then the fault cleared! Next day it re-appeared and attention was (falsely) given to the protection circuits as the amplifier circuits themselves were considered to be in order. The HK uses both voltage and current protection circuits and it was discovered that the current protection circuit was operating. Eventually the fault was found to be one of the 0.39 Ohm 3W metal oxide resistors that had gone high in value on the left hand channel. Of course your amplifiers fault may not be due to this but the reason for going into standby would probably be the same i.e. due to amplifier protection circuits operating. You need to check out all the output devices and those resistors on every channel, even surround ones you may not be using. Hope this helps.