Need help on my Pioneer SD-P4691

Hello....I have a Pioneer (SDP4691K) rear projection TV, that has developed a "power on, power off" problem. With the main power on, I can turn the set off with the remote, but cannot turn the set on with the remote. When I power the set off completely, I can then turn it back on. I do not have a component diagram for this set, or service manual. Can anyone offer assistance, as to what I should check first? Thanks for any and all help! Vincent