B+ Voltage rail; Lenovo Y510p VIQY1 NM-A032

[ITworkshop]

Hi,
I'm a begginer still at repairing motherboards in laptops, but I'm willing to learn.
Its the second time I got a laptop that doesnt draw any power. For this laptop Lenovo Y510p VIQY1 NM-A032: No visual damage, no liquid damage, just doesnt turn on. No shorts on all chokes. Voltage is coming in 20V, then after second power IC after VIN (PQ302) it goes down, to 8V. I have schematics, boardview, multimeter, own regulated power supply, soldering iron and hot air station, and some free time.

Quick question nr. 1: does the B+ Voltage rail, should have any voltage without the battery? Its the same rail for battery charging?

[mon2]

Remove all power.

Meter in resistance mode (lowest scale).

Check the resistance of the mosfet pins to check for possible damage:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate(4) & drain (5-6-7-8)

Post each reading, in order for PQ301 and then PQ302.

Then, check the resistance to ground of pins 5-6-7-8 (drain) of PQ302.

That is, red meter lead to either 5-6-7-8 pins; black meter to ground.

What is the resistance to ground of the P3 rail ?

[ITworkshop]

Measurements: pins on the left red probe, pins on right black probe:
PQ 301:
source (1-2-3) & drain (5-6-7-8): 0,48MOhms
source (1-2-3) & gate (4): 125kOhms
gate(4) & drain (5-6-7-8): 0,7MOhms

PQ 302:
source (1-2-3) & drain (5-6-7-8): 12kOhms
source (1-2-3) & gate (4): 125kOhms
gate(4) & drain (5-6-7-8): 0,5MOhms and rising to 0,9MOhms

Ive tested PQ301 and PQ302 resistance to ground earlier, and some readings were strange. This are the readings:
PQ301:
Pins: 1-3: 60kOhms and rising, 96 and slowly rising; 2nd measure: 0,5MOhms
4: 0,6MOhms 2nd measure: 118kOhms
5-8: 135 kOhms
Maybe im switching gates measuring so fast (no voltage is connected to the motherboard)

PQ302:
Pins: 1-3: 0,4MOhms
4: 0,6MOhms
5-8: 5kOhms rising to 10kOhms; 2nd measure 0,5MOhms falling to 0,4MOhms; this time I was measuring only 1 pin (pin 8), and 2 different measurements were showing up.

To answer your last question resistance P3 to ground is 5-10kohms or 0,4MOhms

[ITworkshop]

Oh, I've misstyped. Voltage VIN 20V, Voltage at PQ302 pins 5-8 is 0,8V, not 8V.

[ITworkshop]

I've checked once more the lowest resistance on PQ302,
Red probe source 1,2,3 , black on drain 5,6,7,8 - 12kOhms. And on the second reading, 60KOhms.

[mon2]

PQ302 has too low of a resistance and should be replaced.

These mosfets are not expensive so recommend to also replace PQ301.

What are the markings on each part ?

Is it AO4423L ?

There are many valid replacements for this mosfet.

https://www.aliexpress.com/premium/A...psort=1&page=1

If you wish to source from a local supplier, post back to see if we can find a drop in replacement from TI or similar.

[ITworkshop]

Well it turns out that the PQ301 is 4423, AO company, but the PQ302 is 4483A with a B logo, or is it crossed S? And a triangle at the right - screenshot in the attachement.

Strange, why would they use different mosfets than on the schematic?
Should i replace both of them for the same mosfet model? 4423 is best for this application?

I've found TC4423AVOA MICROCHIP TECHNOLOGY, at my local supplier, but its a little bit more expensive, than other mosfets that I've already ordered, and after reading datasheet for it, I think its a dual mosfet (DRMOS?).

Couldn't find anything 8pin 30V 17A or higher... Maybe I'm searching this the wrong way. If I could ask you, for finding me a replacement for this IC, I would be grateful:-) my local supplier has this website, with all the ICs: www.tme.eu

I could also desolder them and check the resistance to ground, if You think it would help. Also I've noticed that Resistor PR301 is lower than it should be (when measured on board it has around 138kOhms measuring on both sides, not to ground). When applying 20V, after PR301 there is 6,8V. I doubt that 6V is used on a motherboard:-)

[Stevedb]

The picture is si4483a mosfet.

Regards

[mon2]

Hi.

1) The Microchip part is not the same as the mosfets showing in the schematic so ignore that option.

2) The schematic shows AO4423L for both PQ301 & PQ302 so suggest this as one option - use the same for both landing pads.

3) Other valid options are to replace with a part such as the following:

< the following looks to be a better part than the original >

https://www.mouser.ca/ProductDetail/...ySH5KPIg%3D%3D

p/n SI4459BDY-T1-GE3
P-Channel 30 V (D-S) MOSFET
Supports upto 27A

[ITworkshop]

Ok, thank You very much for help.
I've ordered SI4459ADY, because B wasn't available here. Its little less resistant to pulsed drain current, but still rated above 20 Amps for continous drain current.
I'll write back, after replacing them, probably tommorow, or monday.

[ITworkshop]

I've replaced both mosfets, no changes. 0,8V After PQ302, 0A current.
Whats the next thing I should try/ check / measure?

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance of the replaced mosfets as before.

Post the measurements.

[ITworkshop]

Measurements: pins on the left red probe, pins on right black probe:
PQ 301:
source (1-2-3) & drain (5-6-7-8): 60 KOhms, on second measurement 0,4MOhms
source (1-2-3) & gate (4): 120kOhms
gate(4) & drain (5-6-7-8): 0,6MOhms

PQ 302:
source (1-2-3) & drain (5-6-7-8): 60 KOhms, on second measurement 0,4MOhms
source (1-2-3) & gate (4): 120 kOhms
gate(4) & drain (5-6-7-8): 0,6MOhms

PQ301 and PQ302 resistance to ground the readings:
PQ301:
Pins: 1-3: 60kOhms and rising to 90kOhms; 2nd measure: 0,45MOhms
4: 0,6MOhms
5-8: 130 kOhms

PQ302:
Pins: 1-3: 80 kOhms, then 2nd reading: 0,47MOhms
4: 0,6MOhms
5-8: 5kOhms rising to 10kOhms; 2nd measure 0,5MOhms falling to 0,4MOhms

Almost no difference between old mosfets

[mon2]

Quick question nr. 1: does the B+ Voltage rail, should have any voltage without the battery? Its the same rail for battery charging?

Yes, B+ should be ~VIN from external DC adapter, when the adapter is used. This is the priority. External adapter is selected even if the battery is attached.

BATT+ is a lower voltage than VIN and is used to charge the battery but the BATT+ voltage is defined by switching ON/OFF the mosfets @ PQ311 & PQ312.

The battery mosfet @ PQ310 will be open when the VIN from the external DC adapter is not present (ACDET signal is used to detect if the adapter is present). In this case, the BATT+ voltage will be used to power the B+ rail.

For these tests, remove the battery if it is attached.

Then take voltage measurements of the mosfet pins @ PQ301 & PQ302.

Also measure the voltages (carefully so no pins are shorted with the meter) of PU301.

Post your readings.

[ITworkshop]

PU301: BQ24737
1 ACN: 0,8V
2 ACP: 0,8V
3 CMPOUT: 0V
4 CMPIN: 0,185V
5 -ACOK: 0V
6 ACDET: 2,843V
7 IOUT: 0V
8 SDA: 0,032V
9 SCL: 0,033V
10 ILIM: 0,001V
11 -BM: 0,003V
12 SRN: 1,172V
13 SRP: 1,172V
14 GND ---
15 LODRV: 0V
16 REGN: 6V
17 BTST: 5,78V
18 HIDRV: 1,18V
19 PHASE: 1,18V
20 VCC: 19,5V
21 TP /GND---

power in: 20V

I've noticed that PC308 was partially desoldered, so I've resoldered it before measurements.

[mon2]

See a few faults starting with:

3 CMPOUT: 0V
4 CMPIN: 0,185V

Can you confirm these readings again ? Both should be the same reading or very very close to each other. Use the lowest scale on DC volts scale for your meter.

[ITworkshop]

Before PQ308, VIN is 20V, after R324, only 7V, and PAC outputs (pin 2 and 3) of PQ308 are 0V, so does the ACPRN output (pin 5) has 0V. This probably blocks the AC OK status of pin 5 in PU301? or I'm wrong?:-)

[ITworkshop]

Originally Posted by mon2

See a few faults starting with:

3 CMPOUT: 0V
4 CMPIN: 0,185V

Can you confirm these readings again ? Both should be the same reading or very very close to each other. Use the lowest scale on DC volts scale for your meter.

Pin 3 is 0V
Pin 4 is 0,08V and slooowly falling down

Next measurement:
pin 3: 0V
pin 4: 0,125 and falling down. The longer the power is in, the lower Voltage it has. After reconnecting 20V, it goes up to 0,125V

[mon2]

Sorry, my bad on the comments of:

3 CMPOUT: 0V
4 CMPIN: 0,185V

Thought it was a current sense leg on the charger IC. Ignore this.

[ITworkshop]

Originally Posted by mon2

Sorry, my bad on the comments of:


Thought it was a current sense leg on the charger IC. Ignore this.

Quick question: what does the CMP IN and OUT mean? what is CMP?