Dell D531 not powering on.

[diif]

Hello, I am at the school where i work and i have three Dell D531 laptop motherboards with the same symptoms. I am hoping someone can give me some help.

On pressing the power button the power LED lights for a couple of seconds before going out and the battery LED lighting for a moment.

CPU and memory tested and good. CPU warms up for the couple of seconds the power LED is lit.

The batteries are being charged.

[cyberhack]

Re: Dell D531 not powering on.

Are you using the correct charger.

[selldoor]

Re: Dell D531 not powering on.

More questions than answers:
Are you testing with the heatsink in place - you should be.
Does the fan kick in?
Have you tried on battery only?
Have you tried with no battery?

Is the cmos battery good and connected?
Have you tried with the lan card and the modem card out.
All 3 boards have exactly the same problem?

[diif]

Re: Dell D531 not powering on.

Thanks for your replies.
Yes, it is the correct and genuine charger, tested and verified working.
It was tested with the heatsink in place but i temporarily removed to see if the CPU was getting power and it warms up for the couple of seconds the LED lights.
There is no fan spin. I have tested with charger only and battery only after removing the modem and PCMCIA adapter, CMOS battery checks out. The fault on the other two motherboards looks similar, we have over 100 of the D531 here. I have noticed on a couple of other broken boards that PQ4 the FDS6679AZ has burnt out. I have tested the voltages and apart from the top right pin (3.28v) looking at the board all other voltages are 19.79v.
We have also had the occasional issue with some of the laptops overheating. The kids don't turn them off, with the screen staying lit and then put them in the storage trolley.
It's killed a few CPUs, maybe this is related ?

[selldoor]

Re: Dell D531 not powering on.

Well, heat is a sure motherboard killer. The fan not spinning or twitching at start up is a sign the Mb or cpu has gone bad and you have tested the cpu. tested the fan?

Unless someone on here knows what the fault might be next step would be to
either try and trace the voltages from the power socket using the schematic or laboriously checking every component.
Did you test that mosfet for shorts?

[diif]

Re: Dell D531 not powering on.

Yes, CPU and fan both working.
The mosfet isn't showing any short to ground in place, do i need to desolder to test ?

[selldoor]

Re: Dell D531 not powering on.

Not usually try this test if ist not what you did already.
If any reading is less than 30 ohms you might have shorted mosfet. Remove from circuit and repeat the tests to verify.

Some mosfets are more than 3 pins. To test those, identify the part number and search for its datasheet. Once you find the datasheet, the pins will be designated source (S), gate (G), and drain (D). It will probably be documented as S1, S2, G1, G2, D1, D2.

Simply test

a) black on pin S1- red on pin G1 - record ohms
b) black on pin S1- red on pin D1 - record ohms
c) black on pin G1- red on pin D1 - record ohms

Repeat for the "2" pins. That is S2-G2, S2-D2, G2-D2.



S are all connected and D all connected so just need the 3 tests as above.
I would only take it off to test again if any were less than 30ohms

[spleenharvester]

Re: Dell D531 not powering on.

Just thought I'd add, I've personally owned two of these, and as nice as they were, wow they got baking. It probably wouldn't take much to make them overheat, really.

[diif]

Re: Dell D531 not powering on.

Cheers Selldoor, I've tested and all the values are in the k ohms range so i think the problem lies elsewhere. I shall keep checking components.

[selldoor]

Re: Dell D531 not powering on.

If you have a known good board you can use its often easier to
compare readings rather than checking to a schematic. dot each with a felt tip as you check.

[ramji]

Re: Dell D531 not powering on.

Have you tried turning it on with the battery out and the charger in? Also try resetting power by taking the battery and the charger both out and holding the power button down for 10 seconds.

Also, check out the few methods listed at [Fix] Your Laptop Will Not Turn On

[dj_ricoh]

Re: Dell D531 not powering on.

Cheers Selldoor, I've tested and all the values are in the k ohms range so i think the problem lies elsewhere. I shall keep checking components.

did you manage to fix it?

[diif]

Re: Dell D531 not powering on.

I've not had a chance to have another look at these yet. There are about 400 laptops that need re-imaging at the moment so i have been working those.

[tedtones2600]

Re: Dell D531 not powering on.

up for this.. got same problem, have you fixed it?