lenovo G550 zombie laptop.

[pocgoc]

Re: lenovo G550 zombie laptop.

U50 OUT pins are 5V for USB its resistance should be > 300ohm.

Remove U50 and measure pins.

If OUT pins still low resistance check USB connectors and C442 and C443.

PIN 8 oc# = 0.607Kohms
PIN 7 OUT = 0.607ohms
PIN 6 OUT = can't get a resistance on this pin ? OL
PIN 5 OUT = when i open the gate (i think) i get 3.482 Mega ohms

Sorry im a total noob when it comes to measuring mosfets.

[Tuomo]

Re: lenovo G550 zombie laptop.

PIN 8 oc# = 0.607Kohms
PIN 7 OUT = 0.607ohms
PIN 6 OUT = can't get a resistance on this pin ? OL
PIN 5 OUT = when i open the gate (i think) i get 3.482 Mega ohms

Sorry im a total noob when it comes to measuring mosfets.

My bad, I meant motherboard pads. Sorry..

U50 is likely broken, now you have to check at ouput pins to USB are not shorted.

U50 have to removed from motherboard.

[pocgoc]

Re: lenovo G550 zombie laptop.

My bad, I meant motherboard pads. Sorry..

U50 is likely broken, now you have to check at ouput pins to USB are not shorted.

U50 have to removed from motherboard.

I checked the pins on the USB connectors with the meter , No shorting on the 2 connectors. but C443 came back with a high resistance of 10.67 mega Ohms and still rising slowly
C443 =10.67 Mega ohms.

[Tuomo]

Re: lenovo G550 zombie laptop.

I checked the pins on the USB connectors with the meter , No shorting on the 2 connectors. but C443 came back with a high resistance of 10.67 mega Ohms and still rising slowly
C443 =10.67 Mega ohms.

Ok.

Next check other side of U50 pin 2,3 and C440.

If those are ok it is very likely at just U50 has shorted and broke PU401 also.

Before you buy a new circuit need to make sure thing.

[pocgoc]

Re: lenovo G550 zombie laptop.

Ok.

Next check other side of U50 pin 2,3 and C440.

If those are ok it is very likely at just U50 has shorted and broke PU401 also.

Before you buy a new circuit need to make sure thing.

pin 2 15.9 ohms
pin 3 = 15.9ohms

c440 =16 ohms

[Tuomo]

Re: lenovo G550 zombie laptop.

pin 2 15.9 ohms
pin 3 = 15.9ohms

c440 =16 ohms

Look low but not shorted.

You can measure U53 for comparison.

Is PU401 complete dead?

[pocgoc]

Re: lenovo G550 zombie laptop.

Look low but not shorted.

You can measure U53 for comparison.

Is PU401 complete dead?

I replaced
1. u50
2. pq401
3. c443

I powered it up works but the display/ lcd Back light not working.
I replaced the inverter , got a spare LCD, it still continues to power the back light. Any ideas

[spidey]

Re: lenovo G550 zombie laptop.

check LCVD circuit, inverter pins. vin(+10 - 21V), gnd, on/off (3.3v), brightness(200mv - 3v) if one of them missing trace back to soruce. Still cant find, get vin from dc_bat_out. and others from nearest (s0)state switch..

[pocgoc]

Re: lenovo G550 zombie laptop.

I got a refurb board, and its intel based again, no nvidis gpu. But the screen is blank not dead just blank , graphics is none existent . Is this solution a reball/ reflow . Backlight is ok, the LCD cable is okay, and LCD is working on another laptop and it works fine on a external screen. What you guys think, Southbridge reflow?

[pocgoc]

Re: lenovo G550 zombie laptop.



I think a0# and a0, Should have a voltage , right?

[ethernet]

Re: lenovo G550 zombie laptop.

Check the Close Lid switch to resolve the backlight.

[john76b]

Re: lenovo G550 zombie laptop.

hi, i have toshiba L510 , my problem is same there. laptop totally no power no signal, even AC plug in and battery installed, before it become so serious damage,it will auto shut down often by itself, ad later totally gone on the next day,
cpu chcked ok, Ram ok, hard disk ok, NEc 128 tokin been replace, AC adaptr 19V ok,but still no power and no signal at all.kindly advise if someone know how to resolve it,
i believe there is power problem ,but dont know which one its a root cause..

[john76b]

Re: lenovo G550 zombie laptop.

anybody know how to create new topic?

[Attif]

Re: lenovo G550 zombie laptop.

need bios lenovo g550 ( la-5082p )