Lenovo Y50-70 (not touch) - Screen LED Backlight

[piernov]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

I'm not sure you're mesuring the right thing. You should be getting 19V on both side of that resistor. (or at least the top side if it is burnt). Anyway check its resistance, it should be 0. Next would be to check for a short to ground on the connector.

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

I get 17kohm and 0v (testing gnd from the lcd connector)

[rookieme]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

what voltage do you get at PC1135?
when you got 19V from pin 16 of PU1101 did you got them right from the pin or before PR1115? The second is the correct thing to do.

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

I got it right from the pin. Will check voltage on PC1135

Thanks guys !

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Pc1135 gives 7v also... This is strange...

[rookieme]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

This is strange indeed.
Can you confirm if your board is just like the photo posted by piernov?
The schematic shows that PC1135 is connected at 19V by PL1101, PL11050 & PL1106 but photo shows that is connected by the PU1102.
Can you read the part number of PU1102?

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

It does look the same, here is some pictures

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Pu1102 is

97374m ti 47 apsf

[rookieme]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

ok, PU1102 is CSD97374Q4M [schematic has is wrong written!] which is a buck converter that lowers the voltage of Pc1135 for other circuit.
The issue is that we need 19V at Pc1135 so we need to find PL1101, PL1105 & PL1106 that supply them.
Can you also post a photo from the other side of the board?

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

I will put more pictures later on today, thanks !

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

So, here you go. Looks that jp11 is strange but for the rest nothing special...

[rookieme]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

ok, at the left I can see the three coils [PL1101, PL1105 & PL1106].
Measure the voltage at both of their sides.

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

7.32v on all of them... I checked the little u11 and seems that I get 3.16v on pin 2 and the rest 0v and all components next to it also 0v

[rookieme]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

The 3,16 V at u11 should be the pin 5 [pin 2 is ground]
also I'm guessing that pin 1 will give that voltage when system is running as you can see image at the display.
You said that coils all have 7,32V, one of their side is B+ which is the supplied voltage of your power supply after passing the two dc-in mosfets PQ301 & PQ302.
Take a measurment before PQ301 [pins 5-8] and after PQ302 [pins 5-8].
I want so see what voltage are you getting from your power supply and how much of that is feeded at the system [B+]

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Pq301 pin5-8 get 0v (working on battery so probably normal)

Pq302 pin5-8 get 7.3v

[rookieme]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

can you also try with a power adapter?

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Ok, with power adapter (battery disconnected), get 20.4V

Measured R375 again, got 20.4v on first side and 0v on second, so I guess that this is wrong...

[rookieme]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

ok, it's time to find a simillar size zero ohm resistor or a smd fuse [2,5 - 3A] and do a replacement

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

I've that one from a dead motherboard (Packard bell), is this fine?

[Kashi1712]

Re: Lenovo Y50-70 (not touch) - Screen LED Backlight

Ok, I get 20v now but, still no light...