PARTIAL power? possible? intel imac

Does a power supply have to be either dead or alive, or can it be weak / failing?

i am having a screen flicker issue with my intel imac 24" 2.33ghz.
after replacing the inverter board and still having flicker problems, but none on external monitor i am starting to be convinced it is the power supply. i will try to keep my story and symptoms short and simple.

if i turn down brightness flickering goes away.

if i do anything processor intensive, the flickering comes back until "strain" is released. for example, decide to play command and conquer 3, it will start flickering but go away after i shut down game. it doesn't matter which monitor acts as primary. ( if external is primary cnc makes other monitors go black)

if i use quicktime to simultaneously play avi movies, flickering increases in frequency as i add more and more. i have even been able to make imac shutdown.

if i play a movie and flash an isight pic from photobooth imac shuts down.

i should also mention, internal hard drive is not detected, ive been running off an external. however last night internal groaned and came on. even after rebooting a couple times to see if it would remain, but browsing its contents is usually slow as if it needed more juice. i can only assume it TOO is not getting juice it needs. i have already tried the data cable with a known working one.

i should also mention i have the paneling and case open with the screen sitting seperate connected only by its 2 connectors, and have gotten a fan control utility, and app to monitor temperatures, so cooling it NOT an issue here.

i have also noticed upon bootup when the flickering begins, sometimes the machine will just shutdown unless i leave the internal screen disconnected. i can then "hot plug it" after bootup. maybe coincidence, maybe not, but while playing with it (thru software usage, games,movies etc) i noticed after changing inverter board sometimes the bottom backlight would go out completely while trying to initiate flicker, putting it sleep then waking it brings it back.

whooooo. i hope that was short enough.

anyway insight, helpful experiences, or comments?

i have a multimeter if anyone knows pinout and voltage draws etc. i would love to do some hard testing. i cant afford to throw any more money at this thing.

 

is there any way to check for sure? perhaps w.multi-meter?
ive checked ATX boxes before but it was to see if they were dead or alive. in this case i'm not sure what the technique would be

 

SOLVED. It WAS the power supply