Dell E5550 (LA-A911P Rev 1.0) - strange behavior

[vtfe]

Hello,

I have a Dell Latitude E5550. I don't know the history of the PC. The battery is missing. BTW I am not too sure the laptop will boot at all with mains but without a battery. Can someone confirm this laptop can boot without a battery attached?

At the moment, here is the behavior:
If I plug the charger and I have a USB led lamp plugged in, the lamp turns on steady (Happens with only one USB port out of 3). When I press the power button, nothing happens. USB lamp stays on, but nothing happens.

If I unplug the CMOS 3V battery, the lamp in the USB port will turn on for a split second then off. Just then the power button LED will turn on for a split second. Then off. If I press the power button, the power button light will turn on for two seconds then off.

Any idea? Short in the motherboard? Bad CMOS battery? Bad BIOS?

[Mazorca]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

I have an E5550 and it does indeed turn on without battery, just the AC adapter. I think all laptops do this. Currently have the battery on order, this one has a sort of propietary cable from battery to motherboard. Dell part number NWD9K or 0NWD9K.

[vtfe]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

Thanks, Mazorca!

[vtfe]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

Now does anybody know what could be wrong with the motherboard?

[vtfe]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

Now does anybody know what could be wrong with the motherboard?

Extra info: I have tested the CMOS battery when it is plugged into the motherboard - multimeter indicates 2.7V only.

[Techtiger]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

Now does anybody know what could be wrong with the motherboard?

Extra info: I have tested the CMOS battery when it is plugged into the motherboard - multimeter indicates 2.7V only.

dissemble the laptop first clean it remove HHD COMS inspect visually any burn SMD components change the BIOS battery for a new one hold down the power button fro 10 sec with out any power put back BIOS battery and power & check if the fan is spinning CPU getting worm do not assemble the laptop for the moment keep it out with out screen feedback do you know how to read the Schematic ?

[vtfe]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

Merci, Techtiger!

I have had a close look at the mobo. 2 chips are missing in LI5 and LI6 (see pictures attached).

According to the Schematics (attached) the parts are DLW21HN900HQ2L_4P.

They are Chip Common Mode Choke Coils (datasheet is attached).

I have no idea what these chips are (lol). Instead of replacing them, can I possibly bridge pads, just to see if the motherboard will boot?

[Techtiger]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

Mr Bordeaux
No worries those coils have not been included in this MB by the engineer , find out PQ700 it’s a 8pins Mosfet P-channel what is the voltage on pin 8 1 4 with 4 digits on multimeter 19.XX?
Voltage on PR701 ? PU700 pin 1 2 28 6 5 24 be careful not to short pins when testing page 46 . Find out PL101 Pl102 what are the Voltage on those coils page 41 ?

[vtfe]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

Hello Techtiger,

I have looked for pictures of the motherboard and the coils are present on a factory motherboard (see picture attached). I definitely think they are missing on my motherboard. Having said that, I have no idea if the missing coils are responsible for the motherboard failure.
The USB port with the missing coils is the only one that will turn on a lamp led steadily. On the other two USB ports the lamp will only flash for a split second when charger is plugged in.
I suspect there is something wrong here and I would still like to bypass those coils if it's safe (jumper wire?).

Multimeter readings
Mosfet PQ700
Pin 1: 19.66V
Pin 4: 0V
Pin 8: 19.66V

PR701: 19.67V

PU700: too tiny. I'm not properly equipped (big multimeter probes and bad eyes) and I'd like not to test it right now for fear of shorting something. I will if it is absolutely necessary.

PL101: 3.31

PL102: 5V

Thanks again for your help

[Techtiger]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

Leave the Coils for the moment , PQ700 Gâte 0V pin 4 this is not correct test again if still 0V remove all power put the Multimeter continue to mood test pin 1 8 & 4 what are the reading feed back

Find out PU800 what are the voltage pin 1 2 7 is the IC getting worm keep you finger and see

[vtfe]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

OK, I have tested PQ700 pin 4 again.
With CMOS battery plugged in-> 19.03V (the "original" battery, which is 2.72V)
No CMOS battery -> 0V
I tried with another CMOS battery (2.96V) plugged in but pin 4 -> 0V (???)

Another strange thing is that the power button only reacts when there is no CMOS battery at all or the 2.96V battery is plugged in.

• When mains is plugged the button led turns on briefly.
• A push on the button will light the led again shortly.
• A second push on the button, the led turns on for 2 seconds, then a faint click is heard in the middle of the mobo then the power button led turns off.

I checked PU800 but it is not warm. The chip is so tiny, I'd rather not take the risk to short it while probing it. Unless it is absolutely necessary.

[Techtiger]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

[QUOTE=vtfe;993695]OK, I have tested PQ700 pin 4 again.
With CMOS battery plugged in-> 19.03V (the "original" battery, which is 2.72V)
No CMOS battery -> 0V
I tried with another CMOS battery (2.96V) plugged in but pin 4 -> 0V (???)

Another strange thing is that the power button only reacts when there is no CMOS battery at all or the 2.96V battery is plugged in.[LIST]

it's not clear for me PQ700 pin 4 voltage is 0V when the BIOS batt insert ? & if no BIOS batt you have 19V on pin 4 of PQ700 ?

near the BIOS batt there is a DIODE PD3 test the voltage with bios battry & with out bios batt all 3 pins & find out if it's short or not

remove all power put the Multimeter continue to mood test pin PQ700 1 8 & 4 what are the reading feed back

[vtfe]

Re: Dell E5550 (LA-A911P Rev 1.0) - strange behavior

it's not clear for me PQ700 pin 4 voltage is 0V when the BIOS batt insert ? & if no BIOS batt you have 19V on pin 4 of PQ700 ?

I have 19V on PQ700 pin 4 when BIOS battery is inserted. But then power button shows no sign of life.
If no BIOS battery is plugged in, I have 0V on PQ700 pin 4. But power button led will light when pressed.

near the BIOS batt there is a DIODE PD3 test the voltage with bios battry & with out bios batt all 3 pins & find out if it's short or not

PD3 without BIOS battery: Pin 1, 3.13V // Pin 2, 0.08V // Pin 3, 3.30V
PD3 with BIOS battery: Pin 1, 3.13V // Pin 2, 2.97V // Pin 3, 3.30V

remove all power put the Multimeter continue to mood test pin PQ700 1 8 & 4 what are the reading feed back

PQ700 pins 1 8 & 4 with power removed: multimeter reads "open line"
Just to be sure, this is the "beep mode", right? I have tested all of the pins separately with ground -> open line for each pin. Then I have tested the pins with one another 1 & 4, 1 & 8, 4 & 8. Still "open line". Is that what you needed?