[mdlug] Laptop Hardware issues

[Robert Meier]

Ray,

> The problem: Upon power up a more or less normal POST seems to start,
> but the display never lights, and after about 12 seconds it powers off
> for about 5 seconds, then starts the cycle over.

I suspect a bad power supply.
The display and hard disk draw power.
The power supply may be adequate to start,
but inadequate to supply display,
at which point a "brown-out" triggers shutdown.

> Starting on AC power only, no battery.
> Starting on battery power only, no AC.
> Disconnecting, replacing, swapping all disk drives.
> Swapping in known good RAM (Original RAM passed memtest without problem.)

Good sequence of checks.

> Took the whole thing apart looking for loose or faulty connections.

If you have a bench supply (i.e. external source of regulated DC),
I suggest taking it apart again,
and seeing if it will boot from the bench supply.

Both the laptop battery and laptop AC adapter
use the internal switching power supply.

Normally a switching power supply degrades almost immediately from useful
through brown-out to totally dead, as coils fracture, and capaciters bleed,
but this supply may be degrading more slowly.

> Tried booting mother board with disk drives, track-pad, and keyboard
> disconnected. problem persists
> Reassembled it fail in the same manner as always.

Postulating,
-- 
Bob

  "The gulls who scorn perfection for the sake of travel,
      go nowehere slowly.
   The gulls who scorn travel for the sake of perfection,
      go anywhere instantly."
	-- Chang, Jonathan Livingston Seagull by Richard Bach