HP Pavilion dv7-1232nr laptop power-up problem

[cytherian]

I've got an HP dv7-1232nr that has a power-up problem. It came to me like this and previous owner said it had been working fine, then suddenly started suffering the problem with no warning.

The symptom is that when you press the power button, the laptop tries to start up but shuts down almost immediately (it varies from 0.2 sec to 1.5 sec). The power adapter is fine (I used it on another HP laptop and it charged the battery A-OK). The power LED next to the jack does not light up, only for a brief flash when pulling out the plug. Also, when the plug is installed, the battery light flashes. These laptops do work even without a battery is installed (of course with the AC power plugged in), so I tried this but got no sign of power.

I had read a number of postings on-line about the dv7's problems and the most common culprit to this behavior was a bad power jack. Since it was cheap to get a replacement, I ordered one and installed it. But no joy. Upon disassembling the laptop, I did not observe any scorched components. Everything looked fine.

I ran the laptop through a number of tests. I took out the memory chips and tried to start it without them, as well as with each one individually, and this made no difference. I attached the hard drive to another computer and discovered it is 100% functional. I checked the CMOS battery and it's fine. I also tried to restore the BIOS just in case (http://h10025.www1.hp.com/ewfrf/wc/d...roduct=3860630), which did light up the AC power LED, but the process would not follow through.

On a couple of forums, I'd read about a mosfet failure that could happen in the power circuit path. I've never tested an 8-pin mosfet before. I'd assume that the source and drain is paired up directly (horizontally across). However, there's a 4th drain... so I'm not sure what's to be done with it (or if it's superfluous). The gate is the last pin on the lower left. Also, one technician who posted about a mosfet failure had said he we getting power in both directions, which isn't supposed to happen. Again, not sure how to verify this. Can anyone here explain the general process for testing an 8-pin mosfet? Thanks!

[lord]

Re: HP Pavilion dv7-1232nr laptop power-up problem

Here you have it explained.
It depends if the FET is N or P type will you turn it on with positive or negative lead, but behavior is the same
http://www.youtube.com/watch?v=7piJzaBzZ5o

And here is the pinout for a double mosfet in so-8 housing
http://www.scienceprog.com/wp-conten...et_IRF7105.PNG

and here for standard single mosfet in so-8 housing
http://sigma.octopart.com/177409/ima...d-FDS6690A.jpg

[cytherian]

Re: HP Pavilion dv7-1232nr laptop power-up problem

Thank you for the reply and links, lord. I've been informed that the possible mosfet in question is a P type, the SI-4835dd. I had actually seen that RF mosfet testing video, but didn't think it would apply. But after considering it further, I guess since there's still source, drain, and gate, that you'd do the same thing using the paired source and drain pins.

When doing the test on the motherboard with a multi-meter, is there any danger of ruining the mosfet? Is it pretty safe to test it as long as the right contacts are touched with (+) and (-) leads?

My thought is that if I identify a bad mosfet that I'd go ahead with a replacement. Otherwise, there's a few on-line tech stores that will fix the dv7 motherboard for a fairly reasonable fee ($65~$99), as well as upgrade the heatsink for improved heat dissipation.

[lord]

Re: HP Pavilion dv7-1232nr laptop power-up problem

You can't ruin it, but for testing you have to desolder it from the mainboard.

[cytherian]

Re: HP Pavilion dv7-1232nr laptop power-up problem

You can't ruin it, but for testing you have to desolder it from the mainboard.

Is that only in certain circumstances? I've seen people mention testing of mounted mosfets before, but only for the most basic test (meaning to verify that it functions, but no verification of tolerance).

[cytherian]

Re: HP Pavilion dv7-1232nr laptop power-up problem

* bump *

[anno]

Re: HP Pavilion dv7-1232nr laptop power-up problem

set meter on diode test. then check between Drain and source. look there for more info on testing them
http://mayohardware.blogspot.nl/2011...g-mosfets.html

0 ohm is shorted

[heavymachines]

Re: HP Pavilion dv7-1232nr laptop power-up problem

quick question is the heatsink plugged with dust? do you see a blanket of dust inside the heatsink if so i would say your problem is an reflow issue..... hp are mega big time plagued with this issue it ranges from power on with no display, to not power on at all and power up and shutdown as well, visual artifacts to wireless will not show up in hardware profile....

[cytherian]

Re: HP Pavilion dv7-1232nr laptop power-up problem

set meter on diode test. then check between Drain and source. look there for more info on testing them
http://mayohardware.blogspot.nl/2011...g-mosfets.html

0 ohm is shorted

Thanks very much for the link. I had seen some of Mayo's other postings specific to HP laptops but missed this particular one about MOSFETs. Looks promising.

quick question is the heatsink plugged with dust? do you see a blanket of dust inside the heatsink if so i would say your problem is an reflow issue..... hp are mega big time plagued with this issue it ranges from power on with no display, to not power on at all and power up and shutdown as well, visual artifacts to wireless will not show up in hardware profile....

The heatsink is clean and there's minimal signs of dust (there was just a slight coating on the fan), so I'm not yet sure if it's a reflow issue with the GPU. You're right, some older HP Pavilion models frequently suffered from reflow issues, as well as AC power jacks and MOSFETs. I'm hoping this one is just a MOSFET problem that can be rectified without too much trouble.

[Lobo]

Re: HP Pavilion dv7-1232nr laptop power-up problem

I've got the same problem with an HP pavillion DV7-1243CL. At first, the laptop wouldn't charge or turn on. I replaced the DC in jack cable and the laptop turned on but still wouldn't charge. Minor success.

few months later...it won't charge or turn on again. The adapter is reading 19.5 volts, and 0 on the center pin. Is it possible that a bad mosfet is killing the charger and or the dc in jack cable?

Anyway, I'm definitely checking this out. But I need to set aside some serious time to get to it. These laptops have a TON of screws to deal with before that mobo can come out. ugh

Thanks for the links lord. I'll let you guys know if I find anything.

[lord]

Re: HP Pavilion dv7-1232nr laptop power-up problem

Doubt that the laptop is killing the charger, most likely your charger is bad and you need to replace it or fix it (usually broken cable).

If your laptop is not charging the battery you need to first check your battery, then check battery charger circuit on you motherboard. Look for visual burns on chips, measure chip resistance to ground, and replace the charger controller IC.

[Lobo]

Re: HP Pavilion dv7-1232nr laptop power-up problem

I have a known good charger here that I use for testing and still get the same result. No charge, no power on. So it must be something on the motherboard. It's just weird that this is the second charger for this laptop that died within the last few months.

On a side note...I have small kids running around so its hard to find time to take a laptop like this apart. This has got to be one of the most difficult teardowns I've ever encountered. Last time I disassembled it, I think I counted 30+ screws. And there's still more after that just to get the motherboard out.

I'll post pics if I find anything. Thanks for the help.

[Lobo]

Re: HP Pavilion dv7-1232nr laptop power-up problem

I can't edit my last post for some reason. So sorry

I found my problem. I was going to post some pics, but my camera sucks. The close ups were just too blurry.

Anyway, on the top side of the motherboard close to where the battery plugs in... There's a blown capacitor. Nice and crispy. On the bottom side, almost directly beneath where the DC cable plugs into the mobo...There's a blown resistor labeled PD4. It's so bad that I can't see the color code. I found the schematic, so that should help. I guess I got some soldering to do.

[picean]

Re: HP Pavilion dv7-1232nr laptop power-up problem

Here you have it explained.
It depends if the FET is N or P type will you turn it on with positive or negative lead, but behavior is the same
http://www.youtube.com/watch?v=7piJzaBzZ5o

And here is the pinout for a double mosfet in so-8 housing
http://www.scienceprog.com/wp-conten...et_IRF7105.PNG

and here for standard single mosfet in so-8 housing
http://sigma.octopart.com/177409/ima...d-FDS6690A.jpg

Helo,
Gotta question here. A chip was burnt on my laptop m/board just adjacent to HDD power port.



Its Number is
K261
G546B2

Could you guys please help me in finding its datasheet/cct diagram. Where can I get its replacement?

Thanks

Yaser

[trebo]

Re: HP Pavilion dv7-1232nr laptop power-up problem

no data sheet, but its on ebay, sold from china
the link, http://www.ebay.co.uk/itm/100-NEW-GE...item417a080509

[Fabyj]

Re: HP Pavilion dv7-1232nr laptop power-up problem

Hi guys, I have similar issue:
Mine DV7 (dv7-1060el) - HP motherboard: 480365-001 - JAK00 LA-4082P Rev. 1 - 2008-04-25
Laptop power on with battery only.
When AC adapter only is connected, the right side DC led is off, the left front led (charge) is blinking continuously and laptop no power on.
When AC adapter is connected with battery too the laptop start and when I remove the battery the laptop keep power on!
I verified all mosfet like PQ101, PQ103, ect. and all seems good.
What can be happened?

[Joxatan]

Re: HP Pavilion dv7-1232nr laptop power-up problem

Hi everybody,
I have an HP DV7-3079wm with the same problem.-
Symptom: LEDs glow, fan noise is heard, but display is black and the DV7 shuts down immediately. Indistinctly if is with the battery or the power charger.-

This always occured when the notebook is turned off few time, after that won't start.

I perform a Hard reset, I take off the RAM, HD,
I look the circuit and I don't see any part of the circuit burned.

Any idea?

[bluestone]

Re: HP Pavilion dv7-1232nr laptop power-up problem

I am having the exact same problem, with DV7-4190us, power shuts off immediately after pressing power button, any ideas?

[bluestone]

Re: HP Pavilion dv7-1232nr laptop power-up problem

I have made a new discovery about the shut off situation, After I tried reflow and it was still the same, what I realized is that when you hold the tip of the MoBo where the power jack is connected and bend it down a little u realize the the machine turns on perfectly but goes off immediately you let go.

[JaroTech]

Re: HP Pavilion dv7-1232nr laptop power-up problem

You have a bad solder on a component around the power source.