HP 550 schematic

[Francisco.s]

Re: HP 550 schematic

Can you cut pin 9 of cn17 and inject 5 volts to that pin?
First, be sure it isn't shorted to gnd, or very low resistance.
When there isn't a confidence diagram, very little we can do.
Good luck.

[Dimitrios]

Re: HP 550 schematic

I was trying to find a solid 5V in that part of motherboard but couldn't find. Will bring a cable from the other side to see if that works and open the backlight for me!! Will definitely try to reflow southbridge though!
Without correct schematics is like you are blind and not only that but you are wasting your time!
Again, thank you for answers, appreciate a lot!

[Dimitrios]

Re: HP 550 schematic

So, I did the southbridge/Gpu reflow but unfortunately the same symptoms persists. Tried with different known working set of inverter-video cables-screen but also nothing which is strange. Its either a bad northbridge/gpu which I highly doubt, or a bad smd component which is responsible to give backlight on signal. I have to note that I am getting some sparks coming from DC jack. Dc Jack is fine so I think there is a busted component! There is no proper schematic for this exact model as I confirmed with my readings so this HP 550 is going for spares on my site!

[Francisco.s]

Re: HP 550 schematic

I'm sorry to hear that, but as you said, without schematic is sometimes a waste of time.
Good luck next time.
Regards.

[Atomdesign]

Re: HP 550 schematic

Sorry to necropost, but it pertains to this specific thread so hopefully its ok.

Yesterday, I came across a box containing two HP550 with a malfunctional backlight. I didn't realize it was nearly 1.5 years ago when I last looked at these and started this thread. I now see that Dimitrios attempted to fix a similar schematic deprived HP 550 and failed in the end. Probably a good choice, I took way too much time on this one.

Back to yesterday.. I decided to simply find the CN17 connector pin going to which looked like it needed a voltage, but had none.
Using a small lab power supply I then gave this pin ~3 volts to see what would happen. Voila, backlight on!

I still wanted to fix this properly, so I soldered a small wire to this pin and attached it to my multimeter. Lacking a correct schematic, I decided to systematically check every single component on the motherboard for continuity. Having painstakingly done that (twice) and finding nothing, I gave up and soldered a bridge from pin 5 to pin 8. (stupidly enough, I can't remember which of these two pins already had the 3.2V on it and which one lacked it. I think pin 5 had the voltage it should.

I 'fixed' both laptops this way. I have them on windows 7 now and they both run fine. The repair is a hack, but it works, and its nice to finally have that 'fixed it!' feel. And who knows, maybe someone else can use this to fix their laptop.

[Dimitrios]

Re: HP 550 schematic

Wow just saw the email!! Nice find mate! Well done! Very useful info! I am afraid that I have sold it for parts now but will keep that in mind anyway!

[emoniz]

Re: HP 550 schematic

Hi!
My problem is different but I'm Grabing this post because the motherboard I've trying to repair is exact the same you have. Please can someone tell me what is the reference of the IC U19 and Q628? They are burned as you can see in the photos I'm attaching with this.
If someone can help me I appreciate! Regards

[emoniz]

Re: HP 550 schematic

Hi!
My problem is different but I'm Grabing this post because the motherboard I've trying to repair is exact the same you have. Please can someone tell me what is the reference of the IC U19 and Q628? They are burned as you can see in the photos I'm attaching with this.
If someone can help me I appreciate! Regards

After some search to find the short circuit after removing that two IC, i still have short and the hot goes to graphics card NVIdEA GRrRRR.
If someone still have schematic, it can be usefull to solve other problems in this motherboard, If i still want to repair this one, i need to have the reference for that burned IC's.

Regards

[gsm-expart]

Re: HP 550 schematic

wow

[ntsman]

Re: HP 550 schematic

After some search to find the short circuit after removing that two IC, i still have short and the hot goes to graphics card NVIdEA GRrRRR.
If someone still have schematic, it can be usefull to solve other problems in this motherboard, If i still want to repair this one, i need to have the reference for that burned IC's.

Regards