Replaced logic board, system will still not turn on.

Customer came to me with a macbook pro medel # a1226, late 2008 early 2009 model withthe split back panel. system would not turn on in any form, not even a blink. Cx claimed tehre may have been water damage to teh system and with no electricity running through it we replaced teh logic board, install went greta all excited to start it up and nothing...have triple checked every connector and pin and everythin, no issues, the Old possibly damaged power relay unit that connects the board to the power supply, can it be replaced/ordered and is it possible there is anything else in the system that may dictate a replacement if electrical damage occured? Unfortunately i have only the one unit and the one power supply right now, so i cannot test the unit, with other parts. the power supply is only running about 7 volts through its pins with a voltmeter test. The power module in the upper right corner that magnetizes to the power supply has power running through it if we voltmeter it. is it possible the power switch itself may need replacement? thank you for the replies i wholeheartedly appreciate it. thank you and anyone who replies for your time and assistance.