PowerBook 5300cs Boot Loop

Hi,

Any change if you try to start up with the (main) battery temporarily removed? A bad battery could put a heavy load on the power supply.

Have you checked (with a multimeter) that the power adapter delivers 24 V DC?

Also, you may want to check whether the DC jack on the computer is loose (one can wiggle the plug). If so, resoldering may be required.

Addendum

A output voltage reading for this power adapter could possibly deviate as much as +/- 10 % from 24 V DC.

It may be a good idea to reset the PRAM (and the Power Manager):

a) Turn the PowerBook 5300cs off.

b) Ensure that Caps Lock is not down.

c) Start the computer. At the startup sound, immediately press and hold down the four keys Command(Apple) + Option(Alt) + P + R.

d) Normally, a startup sound should be heard again when holding the keys. However, with this model, you may notice that the computer shuts itself off with a green light instead. If so, release the keys, and then press the Reset button (below the video port) to turn the computer on.

http://manuals.info.apple.com/Apple_Support_Area/Manuals/powerbooks/0306895APB5300UG.PDF

http://manuals.info.apple.com/Apple_Support_Area/Manuals/powerbooks/0308615PB5300Update.PDF

I have a feeling it has something to do with the internals like the battery or the memory. Try replacing a few parts and if it dosn't work your laptops a goner.