Dell Inspiron 3537 - Powers Off

[DanFen]

I've got this Dell Inspiron 3537, LA-9982P, can it powers on during POST (I'm guessing). Occasionally I get the typical Dell message complaining about not using the correct adapter with the right wattage, but that could be because I've removed the battery.

First thing I've found was that the original adapter was fluctuating between 12V and 0V, so going from 12V down to 0V, slowly. Then instantly goes back to 12V, and down back to 0V slowly. Tried two different adapters, just to be sure.

Removed all components I could, left one memory module (one doesn't seem to be working anyway), even removed the screen. Issue persists, shows POST screen, then turns off. So total power on time is like 5 seconds. Won't turn on again unless power button is pressed.

Would appreciated any help, from where to start looking etc... I'm attaching the schematics Thank you

[DanFen]

Just bumping my own thread, checking if anyone can help me into the right direction. Thanks.

[Sametbey]

how many volts do you measure in the pr702 resistance. You should see 19v. you can start from here.

[DanFen]

Hey, thanks for the feedback!

Yes, PR702 seems fine, 19V is present in the area.

Originally Posted by Sametbey

how many volts do you measure in the pr702 resistance. You should see 19v. you can start from here.

Just to clarify, it powers on fine (by fine I mean that display works, Dell logo is up, boot menu is up, and if it stays long enough you can see the typical Dell complaining about bad battery). It however turns off after a few seconds.

[Sametbey]

PQ701 dualmosfet in full control. do not short circuit. Check the stadby circuit on page 38. VREG5 and VREG3,3.

[DanFen]

VREG3 and VREG5 seems fine, 3.3V and 5V respectively.

Am I right to say that this is the voltage step down chip that distributes the lower voltages to the rest of the circuits?

Originally Posted by Sametbey

PQ701 dualmosfet in full control. do not short circuit. Check the stadby circuit on page 38. VREG5 and VREG3,3.

[RememberTheViolin]

Since you observe this chip.
Observe if you have VIN, EN1, EN2, SW1, SW2, pins 12,20,6,18,8.
Voltages. What do you measure?

[DanFen]

VIN > 13.5V
EN1 > 2.5V
EN2 > 0V
SW1 > 5V
SW2 > 3.3V

Question for you, how do you know what's the expected voltage? Is this by experience or by analysing the chip's datasheet?

Originally Posted by RememberTheViolin

Since you observe this chip.
Observe if you have VIN, EN1, EN2, SW1, SW2, pins 12,20,6,18,8.
Voltages.

[RememberTheViolin]

I check the datasheet.

[DanFen]

Looks complex. Am I right to think that EN2 should output 3V?

Originally Posted by RememberTheViolin

I check the datasheet.

[RememberTheViolin]

Yes, this is my thought as well.
It should not be zero. Why not measure it again to verify? Still zero?
If you see my posts i was working on the same chip the last days.
Not output 3v but receive 3V. You see EN1, EN2 stands for ENABLE which is a voltage that tells the chip to output voltage 1, output voltage 2.
The outputs are 3.3V and 5V.

[DanFen]

You're right

EN1 should be 5V right? I can only assume so because the trail says "5V_EN"

VIN > 13.5V
EN1 > 2.7V
EN2 > 3.3V
SW1 > 5V
SW2 > 3.3V

Originally Posted by RememberTheViolin

Yes, this is my thought as well.
It should not be zero. Why not measure it again to verify? Still zero?
If you see my posts i was working on the same chip the last days.
Not output 3v but receive 3v EN is ENABLE which is a voltage that tells the chip to output.
The outputs are other pins.

[RememberTheViolin]

Good this chip is then fine.
Just out of curiosity what voltage on pin 7 (PGOOD for power is good haha)?

[DanFen]

So if I understood correctly, the sequence is more or less:

1. Ensure 19V (or whatever the voltage in is) is being inputted
2. I am not sure why we checked PR702, but I am assuming that the 19V goes through this resistor, powering the charging chip?
3. Check that 3V, 5V are being outputted from the Step down controller.

Originally Posted by RememberTheViolin

Good this chip is then fine.

[DanFen]

Now it's nothing, cause it literally exploded on me.

But I noticed that the EN2 was 0V again, PGOOD was measuring 0.1V at the time. Then I checked VIN, got 13.5V and it exploded

I have some other laptop boards I can look for the same chip, however I'm not confident that I'll find the same exact chip!

Originally Posted by RememberTheViolin

Good this chip is then fine.
Just out of curiosity what voltage on pin 7 (PGOOD for power is good haha)?