Won't power up after last shutdown?

Apple Ibook G4 - 14"

I have a refurbished Ibook G4...I have successfully replaced the dc inboard and the superdrive and all was well....the battery stopped holding it's charge and I only used it with the mac ac adapter which I also replaced with another identical mac adapter when the first one died. Recently the adapter would sporadically work and then not work with the ring color going out...I could move the adapter in the dc board and it would work again, then the adapter stopped all together.

I shut down the computer on the last of the batteries power...the battery would run the computer for a few minutes when the power supply stopped functioning. I replaced the adapter with a third party adapter which was recommended as a replacement on ifixit. Now the problem...the computer will not power up...no noises, no fan, nothing...the battery only does the blinky light thing while in the past it would do a charged lighting response...the present ac adapter does not have a lit ring on it, but when tested at the mac store no ring light on their adapter either and no power up. I have done all the hold this press that for this long restarts and also attempted to reset the PMU etc...

I'm tempted to replace the dc in board but also wondering if I should just get a case for the drive and purchase a newer mac...I'd like to fix it...maybe test the dc inboard to see if that's the problem but not sure how to do this with my multimeter....any help would be great...I thought the only problem was the adapter at the time I last shut down...???...I love using ifixit as I've always been successful in the past...thanks....