HP ProBook 4510s Short Circuit

[branch592]

Got an HP ProBook 4510s as a stripped down shell from my local Goodwill Store. Was able to easily get it working. Unfortunately, there was a loose screw in the machine. While using it, I closed the lid to put it to sleep then turned it over to read the model number off the bottom of the machine. When turned right side up, the machine would not come to life. Seems the screw shorted something out. Found it stuck against the metal frame on the bottom of the board that holds the heatsink on. My iGo power adapter shuts down every time I plug it in to the motherboard. Hard to check the board with no power. Don't have the battery for this machine at present.

Started by checking all the MOSFETs (see below) seen in the schematics. HP ProBook 4510s (pn FN068UT) Laptop Motherboard Schematic diagram.pdf (Attachment from another forum post). Its similar to my machine but uses DDR2 memory instead of DDR3 on my board. Looked for readings less than 30 ohms. Found several. Q5, Q12, Q16, and Q1017 are all low side transistors for the power controllers. Q1054 is my choice for the culprit (page 7 of the schematics). The ohms readings for it are way off compared to the others of its type on the board (Q3, Q6, Q11, Q1016). (link to datasheet)

So the questions are:

1. Is this the likely cause of the short circuit?
2. Are there any more parts I should check?
3. This is a very small surface mount part. 3.3 mm or 1/8 inch square leadless package. Can this be safely removed with ChipQuik or do I need to seek out the services of someone equiped with "proper" desoldering tools? All I have is a soldering iron and a Black and Decker heat gun (I think its 850 degrees on low and 1100 degrees on high).

Thanks.



MOSFET Readings:

Q2 FDS6690AS
Source to Gate = 106.2K
Source to Drain = 3033
Gate to Drain = 106K

Q3 SI7326DN <<< Same As Q1054
Source to Gate = 104K
Source to Drain = 1718
Gate to Drain = 97.3K

Q5 FDS6690AS
Source to Gate = 106.2K
Source to Drain = 30.1 <<<<<<<<<<<<<------------- ????????????
Gate to Drain = 106.3K

Q6 SI7326DN <<< Same As Q1054
Source to Gate = 105K
Source to Drain = 1137
Gate to Drain = 104.1K

Q10 SI7686DP
Source to Gate = 100.9K
Source to Drain = 1129
Gate to Drain = 97.9K

Q11 SI7326DN <<< Same As Q1054
Source to Gate = 90.1K
Source to Drain = 1281
Gate to Drain = 95.2K

Q12 FDMS8660S
Source to Gate = 98.9K
Source to Drain = 21.3 <<< Same As Q16 -- Probably OK
Gate to Drain = 92.9K

Q14 FDC655BN --- Marked as 5581 --- 6-pin
Source to Gate = 4.35M
Source to Drain = 24.41K
Gate to Drain = 4.33M

Q15 SI7726DN --- Marked as 7702
Source to Gate = 91.1K
Source to Drain = 15.5K
Gate to Drain = 97.1K

Q16 FDMS8660S
Source to Gate = 99.5K
Source to Drain = 21.4 <<< Same As Q12 -- Probably OK
Gate to Drain = 92.2K

Q19 SI7686DP
Source to Gate = 101.5K
Source to Drain = 1134
Gate to Drain = 98.5K

Q21 FDC655BN --- Marked as 5581 --- 6-pin
Source to Gate = 3.47M
Source to Drain = 2047
Gate to Drain = 3.44M

Q22 SI7726DN --- Marked as 7702
Source to Gate = 91K
Source to Drain = 1120
Gate to Drain = 91.5K

Q1016 SI7326DN <<< Same As Q1054
Source to Gate = 101.2K
Source to Drain = 1153
Gate to Drain = 7.17K

Q1017 FDS6676AS
Source to Gate = 106.4K
Source to Drain = 51.1 <<<<<<<<<<<<<<--------------- ?????????
Gate to Drain = 109K

Q1029 TPC8121
Source to Gate = 15.87K
Source to Drain = 124K
Gate to Drain = 137.3K

Q1030 FDMC8884
Source to Gate = .524M
Source to Drain = 32.45K
Gate to Drain = .519M

Q1031 FDMC4435BZ
Source to Gate = 46.7K
Source to Drain = 7.08K
Gate to Drain = 57.9K

Q1032 FDMC4435BZ
Source to Gate = 218.8K
Source to Drain = 24.51K
Gate to Drain = 246.0K

Q1054 SI7326DN
Source to Gate = 16.9
Source to Drain = 4.5 <<<<<<<<<<<<<------------- Culprit !!!
Gate to Drain = 20.2

Q1063 FDMC8884
Source to Gate = 96.6K
Source to Drain = 123.1K
Gate to Drain = 211K

[b700029]

Re: HP ProBook 4510s Short Circuit

1. It depends what got shorted.

2. Check the MOSFETs first. With them removed you can also check if any of the main power rails still have a short on them.

3. Very small indeed. You will need hot air but 850/1100 sounds way too hot. A proper hot air rework station is recommended.

You cannot check parts accurately in-circuit, especially ones with high-impedance inputs like MOSFETs. Even the multimeter charging up the gate can cause them to conduct.

I would remove Q1054, Q22, Q11, and Q15 and see if that clears the short. If it does, then check each one separately out-of-circuit. With them still removed, plug in the adapter and ensure you get 3.3Vsb and 5Vsb (pins 8 and 17 of U10). Then unplug and ensure there are no shorts on the main 5V and 3.3V rails.

[branch592]

Re: HP ProBook 4510s Short Circuit

Going to get a local guy to replace several suspect transistors (Q1054, Q1055, Q1056) on this motherboard. He's been repairing laptops for over a decade. Don't have the money to buy a good rework station since I didn't win the MegaMillions jackpot.

Hopefully that will get things running.

One final question. The schematics show Q1055 as a PMV65XP. But the markings on the PMV65XP on the board, there are several, don't match. Those markings look like WM9, but the closest I found was a NXP Semiconductors PMV65XP marked as %M9. Are these the same? The dimensions of my chip is approximately 3mm by 1mm. Have attached a photo of another chip the schematic refers to as an PMV65XP with the same markings. Thanks for the help.

[jetadm123]

Re: HP ProBook 4510s Short Circuit

Since they are probably using an internal factory code, it's a good thing you have the schematic. I suspect the difference between the "W" and the "%" would identify which country or factory the chip was made at. Several companies use such product codes on their smd components and without a schematic, it can be very difficult to identify the component.

[megatech]

Re: HP ProBook 4510s Short Circuit

It's helpfull

[neelix baby]

Re: HP ProBook 4510s Short Circuit

HP ProBook 4520s XT943UT schematic anyone?