Dell E7440 turns on for 10-15 seconds then turns off

[PinGuy]

I got this machine and it would do as described in the title (which from what I saw is a classic for this model). BIOS battery was 2.3V. I replaced it, and it kept doing the same. Also tried with no battery, and same thing. So I grabbed the BIOS files from this post:
https://www.badcaps.net/forum/showpo...7&postcount=69
After burning both BIOSes, the machine started and worked perfectly on the first try. Then I left it unused in a cabinet for about 2 months, now when I was going to use it the same thing happened
I checked the battery and it is at 3.05V. Tried turning it on without the battery: no dice.
So now I grabbed the "latest version" BIOS from this post:
https://www.badcaps.net/forum/showpo...0&postcount=64
And after burning both BIOSes again, it showed no change: turns on and after 10-15 secs it goes off with a single blink from the charging light before turning off.
Does anyone have a clue for this issue, other than throwing it away?
TIA

[mon2]

Re: Dell E7440 turns on for 10-15 seconds then turns off

Are you using the original and recommended power adapter for this unit?

Meter in DC volts mode (20V or higher is ok). Attach the power adapter.

What is the voltage to ground @ PL3 ? (either side is ok)

[PinGuy]

Re: Dell E7440 turns on for 10-15 seconds then turns off

The AC adapter is the original 19.5V @ 4.62A, it measures 19.7V and voltage doesn't drop when turned on in those 10 seconds the power light is on.
I tried this adapter in a working Dell which uses a 3.34A adapter and it works fine.
I tried the adapter from that another Dell on this non-working one and the issue is the same.
In PL3 I only see a small pulse when plugging the charger, and another small pulse after the 10~15 secs when the charge light turns on, right before the laptop turns off.

[mon2]

Re: Dell E7440 turns on for 10-15 seconds then turns off

Remove all power. Meter in diode mode.

Red meter probe to ground.
Black meter probe to pl3.

What is the diode mode reading for the PSID line?

[PinGuy]

Re: Dell E7440 turns on for 10-15 seconds then turns off

The reading is 1.082v, and reversing the leads is OL

[mon2]

Re: Dell E7440 turns on for 10-15 seconds then turns off

Remove all power. Meter in resistance mode.

Measure the resistance of pr9. It should be ~33R ohms.

Often mosfet at pq2 will get damaged.

Flux and remove pq2. Then solder blob pr7 pads for a bypass.

This is to allow for the single wire adapter handshake to reach the EC.

[PinGuy]

Re: Dell E7440 turns on for 10-15 seconds then turns off

PR9 measures fine, and I see the PSID pulses coming from PL3 at pin 4 of PU111 as well.

[mon2]

Re: Dell E7440 turns on for 10-15 seconds then turns off

Remove all power. Meter in resistance mode.

Check the resistance to ground at each coil / inductor on the board.

Each coil / inductor is linked to a local buck switching power supply rail. If there is a low resistance on the rail, the local power supply may be causing the power supply IC to shutdown.

Assuming that the power adapter is the original known good and recommended power rated one for this laptop.

It will be of interest to review the charger IC section to study if the DCin mosfets are being enabled or not.

Connect the power adapter and measure carefully the voltage to ground of each pin on the charger IC.

Post the list of the voltage readings and their pin numbers.

[PinGuy]

Re: Dell E7440 turns on for 10-15 seconds then turns off

None of the coils show a short to ground.
The DC mosfets are switching CHAGER_SRC at 13.5v. ACOK is 3.3v so I believe that section is fine.

[Michael Farrey]

Re: Dell E7440 turns on for 10-15 seconds then turns off

I had a Dell that was doing something similar. It was the result of a bad bios battery. Also, the power supply got a bad reading with the little plug tester which was replaced prior to the fresh bios batt.

[PinGuy]

Re: Dell E7440 turns on for 10-15 seconds then turns off

It was the original issue and it would not start even after changing the CMOS battery. Like as if the BIOS "forgot" its stuff when the CMOS battery died. I reflashed the BIOS and then it started to boot properly.
But then it died again after not using it for a while, and the CMOS battery is fine at 3V this time. I believe it should start even without the CMOS battery, just taking longer to boot, but this one doesn't and the LED pattern is always the same, with or without the CMOS battery.
The charger is tested fine, and there are no shorts on the mobo. Looks like some some "Management Engine" related shite that fails on powerup.
Does the BIOS at U7 control the boot process? I haven't flashed that one.

[Magnusa2]

DELL E7440 NO POWER VOLTAGE IS OK. WHEN I PRESS POWER BUTTON JUST LIGHT ON POWER BUTTON LED FOR 15 SECONDS
I HAVE SAME ISSUE MORE THAN 10 PIECES

[mon2]

Hi.

1) Do not use upper case letters only - it appears like you are yelling and is difficult to read.

2) Be sure you are using the proper power adapter for these units. A standard power supply will not work due to the special single wire communication inside the Dell branded power adapter.

3) Check for this single wire communication with your meter in DC volts mode. Attach the power adapter and check the voltage to ground on each side of PL3. Often PQ2 mosfet gets damaged and cannot pass through the communication between the SIO chip (8051 based) and the power adapter. Then the motherboard is unable to determine the power rating of the connected power adapter and powers down the board. Lots of articles on this forum for such repair. Start with this review.

[Magnusa2]

Hi.

1) Do not use upper case letters only - it appears like you are yelling and is difficult to read.

2) Be sure you are using the proper power adapter for these units. A standard power supply will not work due to the special single wire communication inside the Dell branded power adapter.

3) Check for this single wire communication with your meter in DC volts mode. Attach the power adapter and check the voltage to ground on each side of PL3. Often PQ2 mosfet gets damaged and cannot pass through the communication between the SIO chip (8051 based) and the power adapter. Then the motherboard is unable to determine the power rating of the connected power adapter and powers down the board. Lots of articles on this forum for such repair. Start with this review.

Hii Sir
i have same good board .for comparing. i check PL3 = 3.3v ok. PQ2 S= 3.3v D= 3.3v G= 5v ok
i put good CMOS both boards in good board PD3 D = 3v,, no power board PD3 D= 2.8v . any problem

[mon2]

These voltages are ok.

During the 10-15 seconds of ON time - do you see any text / graphics / Dell logos ?

What are the voltages to ground for the following ?

+3.3V_ALW

PBAT_SMBCLK
PBAT_SMBDAT

CHARGER_SMBCLK
CHARGER_SMBDAT

LCD_SMBCLK
LCD_SMDATA

[Magnusa2]

These voltages are ok.

During the 10-15 seconds of ON time - do you see any text / graphics / Dell logos ?

What are the voltages to ground for the following ?

+3.3V_ALW

PBAT_SMBCLK
PBAT_SMBDAT

CHARGER_SMBCLK
CHARGER_SMBDAT

LCD_SMBCLK
LCD_SMDATA

all voltages ok 3.3v

[mon2]

Do you see any video during the 10-15 seconds of ON time?

[Magnusa2]

Do you see any video during the 10-15 seconds of ON time?

no actually this not on. just power button light on. in DC POWER SUPPLY amp 0.0005

[mon2]

Review the DCin mosfets. Connect the power adapter that is recommended for this box.

Measure the voltage to ground of the mosfet @ PQ4. Measure the voltage @ source (1-2-3); gate (4) and also the drain pins (5-6-7-8). Post each measurement.

[Magnusa2]

Review the DCin mosfets. Connect the power adapter that is recommended for this box.

Measure the voltage to ground of the mosfet @ PQ4. Measure the voltage @ source (1-2-3); gate (4) and also the drain pins (5-6-7-8). Post each measurement.

PQ4 S= 19.4v , D = 19.4v ,, G = 9.3v