hp DV6-3132 laptop no power indication at all appears dead

[wedgetail]

I have been searching foum to gain information on board level laptop repair got a solid start but now stuck.

My neighbour lamented that his hp DV6-3132 laptop was dead. It is now an old model but he hardly uses it and looks in very good condition. Following for my own record.

Intel core i7 inside
ATI Mobility Radeon Premium Graphics: SupportsMicrosoft Direct X11
Windows 7


I have some experience in electronics I promised to have a look and see if I could figure out what was wrong.  I hate to see pallet loads of laptops going to the dump.  For some time I have wanted to get some practical experience so I have started investigating this hp.

Internet search have given me:
1.. The model have significant problems with the graphics chips with flip chip design, not sure if it was only NVIDIA or included ATI, this model has the Intel/ATI. Sobering start odds are stacked against me.

2.. I believe I have the correct schematic, designations corresponds with motherboard, now completely removed.  The devices are different manufacturers but not putting me off yet.

Few details from the 1st page on the schematic (I am not experienced reading the schematics so may be missing some valuable information.)

LX6/7 (Liverpool) BLOCK DIAGRAM
Intel Clarksfield /  Arrandale  CPU 45Watt/35Watt / 4 Core  ( rPGA 989 )  PAGE 3-6
ATI Park XT  (64bit) / Madison Pro (128bit) (FCBGA) / 962p 29X29mm / PAGE 14-18

I have not yet removed the processor or graphics chip, so exact models not known yet.

Manual origin in the file name.  I ended up with quite a number of manuals before I finally had enough understanding of what to look for.

I am now stuck in the charger circuit, with absolutely no power indication when the power supply is plugged in, I think I was expecting a dead short but was soon proved wrong. Power does get to the motherboard. I have attached pdf file page 42 from the manual, annotated with Master pdf Editor running on a Linux computer.

Annotation shows
VA, VAD and VAD_1 which are all present approximately 19V DC, power reaches the drain of PQ42, near the big X annotated in a circle.  The Gate is zero and the source is 0V.

Which from what I can figure prevents the charge controller chip PU5 /OZ8681 working, because the main power line is dead.

This is the point where I get lost, what do I look for to get the charger controller tested?

One more point, the power connector has a centre pin, and despite having the jack assembly removed I have been unable to get a continuity check confirmed.  Since I have power on the motherboard I have ignored this as I have not found out how that actually works or signals.

Feel uncomfortable with not knowing how this "power good" signal works as it may hold an important clue

How should I proceed from here.

[wedgetail]

The power connector center pin, bothered me so searching the net I found information indicating that the power supply probably should have 19V on the sense pin or smart pin or ...

Initially I failed picking that signal up, physically when I tried to make contact with my multimeter it failed, showing 0V, I was using a insulated cannon connector barrel with heatshrink. Scratching my head why that failed as I thought it was a perfect way to avaoid shorting the center pin to inner power barrel, also 19V. Real let down.

Now I can confirm the power supply does have +19 V on the center pin when not plugged in.  When plugged in that signal looks like being shorted to ground. This is AD_ID signal on p42 near CN15 power connector (10 pin) on motherboard.

The AD_ID goes to page 32, bottom right hand corner, just above the title block. Through a simple network and ends up on the Keyboard(??) chip, U7. Ouch will attach p.32

My diode checker on the multimeter sends approx 47 microamps through the wires.

Remove power supply:
"Diode" checking on the AD_ID pin on p42:
Red probe on pin, Black probe to gnd:  640 mV
Reversing the leads:   470 mV

Not a short circuit but enough to drag center pin voltage down to "zero", actually I had multimeter setting on 200V because it over ranges on the 20V range when measuring "the + 19V"  going to the 2V range I get  about 720mV on the the sense pin, center pin on power plug when plugged in. (I am measuring on the motherboard, the 10 pin connector)

The 1SS355 diode spec sheet shows 1mA forward current approx 600 mV drop. With 100 ohms in series and #V power supply dead would probably give about 700 mV drop.

Where does this center pin voltage come from, looks like must be a high output impedance?

Ooooops, I forgot to mention when the power is applied the motherboard area near the power connector warms up to approx 35 deg C, warm to the touch.

Looking at the circuit here, I think I was expecting that center pin voltage to be more of a logic level less than 3.3V as it goes almost direct to an input on the U7 chip.

[wedgetail]

Having used the net and looked in several data sheets for a number of components I am feeling a bit more at home in the general layout of the charging system.

Right now it looks like +VIN is shorted to ground, found that when checking PD23, a protection diode of some form.  Planning careful external variable voltage application to +VIN and see what may get hot.

[wedgetail]

Having a better understanding of the power rails and picked up tips from the internet I tried smoking out the short. with the motherboard out I applied power between +Vin and GND.

When adding 20W things got hot on an area where 8 MOSfets where located ant it look like all 8 has shorted.  One set of 4 produces Vcore.

Not clear If I damaged the processor in the process. Lack of experience, I tried to leave the dismantling of the fan/cooling fins just one step too late.  The voltage got up over 2V during short smoke test.