The lombard ans wallstreet use the same PSU; but the wallstreet's processor module can become pretty easily unseated so I'd give that a try, also try pressing the power management keycombo thats printed on the back. If nothing works there could be a ton of things causing the problem; bad power board, bad connection between connector and power board, bad mobo, bad proc, etc.
If the PMU reset does work, it will light the sleep light for several seconds and rev up the fan, which will produce an absolutely horrifying screeching noise. After that the screen will blank for several seconds as it tests the ram, it'll chime, and hopefully you'll get the grey screen and all that stuff.