Re: I thought that Dell power supplies were different?


Assuming the power supply (red) switch is already set to the correct 115v
rather than accidentally to 220v...... (which would cause the machine to
appear almost completely dead)....


If, with the power switch disconnected from the system board, the rear diag
LEDs (and maybe the case fan as well) "bump" briefly when plugging the
system to main, it's likely one of the components in the front I/O boards or
switch are bad.

It could be the any of them...

power switch board>>>>flat power cable>>>>secondary I/O (USB, Audio, Power)
board >>>> secondary flat cable from I/O board to system board.

-The power switch board could be bad.
-The power cable to the secondary board could be bad, mis-pinned, or
connector pins bent on either board.
-The secondary I/O power board could be bad or damaged.
-The secondary flat cable could be damaged (look for crimps/damage in the
cable insulation).
-The connector pins on the motherboard could be damaged.


All of the components are interchangeable with this assembly from the 4400
with one caveat; the 4400 is a USB 1.1 machine while the 4550 is USB 2.0.
It could be (and probably should be that the system board will dictate those
speeds in any event.)

Getting to the above components is extremely difficult, particularly the
power switch board, as the front bezel plastics (and other base plastics)
have to be removed to get to it. The secondary I/O board is a pain, but
could be carefully swapped and re-cabled as a test if you want to go that
far.

The power supplies in both machines are interchangeable.

No disrepect to Ben, but I'd be willing to swap the boards over to test the
4550 board in the 4400 just to confirm POST and video. You could then focus
on either the power switch assembly or the power supply.

From what you're describing it sounds like some portion of the 4550's switch
assembly. I've seen them do this many times, but it's been several years
since the last one.


Good luck.

Stew


.

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