Dell Precision 7530 Dead

[shybear]

This laptop with Compal LA-F591P Rev.1.0 mb doesn't power on and doesn't charge battery. I've already dismounted all and removed everything, resetting BIOS, check power ON button.
I found boardview and schematic so I started first of all an accurate check of mosfet, transistors and dioodes and others power components. Next I tested voltage and I found on board correctly 19,5V, 5V, 3,3V, 1,1,5V. On positive pin of battery on pins 1,2,3 there shoud be 13,5V but its 0 and so I searched back from it and +20V_VBUS_1 is absent.
Going back to this +20V I checked all mosfet and diodes that are fine and at the end I found PR2134 (100K) was shorted. I replaced it with a working one but still nothing.
I wanted to flash BIOS but I don't have a right programmer for the W25Q256JV chip .
I tried also and USB typeC and it give 20V with 0,0024A but doesn't power on.

[mon2]

What is the voltage to ground of PQ700 (1-2-3)?

Next, check the voltage to ground of the charging circuit coil PL701 (either side). Post the measurement. The battery should be connected. This voltage should be slightly higher than the voltage on the battery pack to permit the charging of the battery. If it is not, remove all power & disconnect the battery.

Then, meter in resistance mode and test the resistance between pins SRP & SRN (20 & 19) of the charger IC. What is the measurement in ohms? It should be ~20R ohms. If it is not, then this leg of the circuit must be reviewed to match the schematic values.

[shybear]

I take values with board dismounted, graphic card disconnected and DC oower board disconnected. Power from type-C give 20V 0.043A no matter if battery is plugged or not.

What is the voltage to ground of PQ700 (1-2-3)?

PQ700 => SI7149DP => pins (1-2-3) 19,55V / pin (4) 9V / pins (5-6-7-8) 19,55V


Next, check the voltage to ground of the charging circuit coil PL701 (either side). Post the measurement.

PL701 => 2.2UH_7.8A => 10,8V on both pins with battery plugged and just 192mV with battery discconcted!

The battery should be connected. This voltage should be slightly higher than the voltage on the battery pack to permit the charging of the battery. If it is not, remove all power & disconnect the battery.

Then, meter in resistance mode and test the resistance between pins SRP & SRN (20 & 19) of the charger IC. What is the measurement in ohms? It should be ~20R ohms. If it is not, then this leg of the circuit must be reviewed to match the schematic values.

IC charger PU700 => BQ24780SRUYR without battery an power give me around 12Mohm betwwn 18 (PR710 4K) and 19 (PR728 10K)

[mon2]

12Mohm betwwn 18 (PR710 4K) and 19 (PR728 10K)

?? Something is seriously wrong here. Confirm that you have fresh batteries in your meter and then touch the probes together using the lowest resistance mode scale. It should be close to 0R ohms. Post this measurement. This is your baseline.

Then measure again the resistance between pins 18 & 19 on this IC. Be sure that you are on the proper pin locations. No power to the board. If the measurements are accurate as posted, the charger IC will definitely not charge the battery due to the high resistance values. The circuit is expecting the full path resistance to be ~20R ohms.

[shybear]

I just tested it agin if I reverse test point I have around 126K. I also tested it with an other meter!

[mon2]

100% a problem here. Continue to use the lowest scale on the meter if a manual type. Then trace from the charger pin to the first resistor. Should be ~0R ohms. Repeat for the 2nd resistor to the IC. Again should be ~0R ohms. Then each resistor must be ~10R ohms. If not, they must be replaced. Total resistance should be ~20R ohms from start to finish. Without this proper resistance, the charger IC will refuse to charge the battery.

[shybear]

Sorry my mistake, in post #3 you asked me value between PIN19 - PIN20
"Then, meter in resistance mode and test the resistance between pins SRP & SRN (20 & 19) of the charger IC"
PIN 20 goes to PR727 (10R) and on the other side to PC718 and PC719 and PR715 pin1&2 (0,01R) , so if I test resistance between PIN 20 - PR715 I've around 10R ohm.
PIN 19 goes to PR728 (10R) and on the other side to PC719 and PC720 and PR715 pin3&4 (0,01R), so if I test resistance between PIN 19 - PR715 I've around 10R ohm.
So, as you said:
IC charger PU700 => BQ24780SRUYR without battery an power give me around 20Rohm between20 (PR727) and 19 (PR728 10R)

Instead
IC charger PU700 => BQ24780SRUYR without battery an power give me around 12Mohm between 18 (PR710 4K) and 19 (PR728 10R)

[mon2]

What are the voltage markings on the battery pack for this model? Be sure the battery is the original or known good compatible.

[shybear]

It's still the original one mounted. 97Wh Type NYRJH 11,4V

[mon2]

Attach the battery and the power adapter. What is the voltage to ground of pin 20? Pin 19?

[shybear]

Attach the battery and the power adapter. What is the voltage to ground of pin 20? Pin 19?

With battery and power (on USB-C) on IC PU700 I've (referred to GND):

PIN 20 => 10,8V
PIN 19 => 4,9V

Just for refernce actually I'm using a standard USB-C power adapter that give 20V - 3,25A (65W)

[mon2]

Pin 20 and 19 should be the same voltage. There is a very low resistance between the 2 pins. Double check the measurements again. These will be the current sense pins.

Update: It is pins 20 & 19 and they should be the same voltage.

[shybear]

Pin 20 and 19 should be the same voltage. There is a very low resistance between the 2 pins. Double check the measurements again. These will be the current sense pins.

Update: It is pins 20 & 19 and they should be the same voltage.

PIN 20 & PIN 19 10,8V
PIN 18 4,9V

Sorry!

[mon2]

What is the voltage to ground of:

PR62 ; test both sides (checking PBAT_PRES#)
PBATT1 connector ; test the battery voltage

[shybear]

What is the voltage to ground of:

PR62 ; test both sides (checking PBAT_PRES#)
PBATT1 connector ; test the battery voltage

PR62 100K (OK) PBAT_PRES# => 3.3mV and other pin (1) => 3,3V
PBATT1 (pins 1-2-3) => 10,8V with battery connected doesnt' change with or withour power supply and 194mV just with battery

[mon2]

Have you tested with another known good battery? Battery charging is one issue but board not powering on is another. You should see video and boot up of the motherboard even if the charging leg of the circuit is not working. Test the voltage to ground of the CPU rails.

[shybear]

Could you give me some voltage reference points of cpu rails? I focused on voltage battery because it seem the other voltage are present on the board.
The only thing I've discovered is that PR2134 was shorted that is part of the +5V_Vbus circuit

[shybear]

Have you tested with another known good battery? Battery charging is one issue but board not powering on is another. You should see video and boot up of the motherboard even if the charging leg of the circuit is not working. Test the voltage to ground of the CPU rails.

OK, I also think that even if battery doesn't charge laptop should powering anyway. I don't have an othery battery to test, anyway I think that first step its that mainboard power on.
So i focused and tested VBUS valuesand I get these results:
+20V_VBUS_1 => 30mV
+5V_VBUS_1 => 0V
+20V_VBUS_2 => 19,78V
+5V_VBUS_2 => 4,88V
So there is something else wrong on VBUS1 section but testing components (except PR2134 that I've replaced) seems to be fine. Any suggestion?

[mon2]

This is usb-c so the connector head is reversible. Unplug from the wall, then flip the motherboard side adapter head by 180 degrees to use other side. The the vbus_1 rail should be active. Confirm it.

[shybear]

This is usb-c so the connector head is reversible. Unplug from the wall, then flip the motherboard side adapter head by 180 degrees to use other side. The the vbus_1 rail should be active. Confirm it.

Yep you're basically right but not just flip connector, it dependd from the used port of JUSBC1 used so:

using the upper one (PIN 1Bxx) => works PQ2105 so:
+20V_VBUS_1 => 19,78V
+5V_VBUS_1 => 4,88V
(VBUS_2 not working)
using the lower one (PIN Bxx)=> works PQ2101 so:
+20V_VBUS_2 => 19,78V
+5V_VBUS_2 => 4,88V
(VBUS_1 not working)
Any other voltage test could I try?