lenovo G450 no back light on led screen.

[rickybucalan]

hi guys anyone can help me pls.

i got got lenovo g450 and it is working but no backlight on the screen.
1. i have try another screen but it just the same.
2. i also try to trace cut wires of lcd cable going to the MB. continuity test ok.
3. and i also did test voltage on lcd connector 40pin. i got 20v on pin 28, 29, 30
3.3v on pin 2,3,4.

and i don't no what to do next..

hope u help me guys god bless all.

[sasser]

Re: lenovo G450 no back light on led screen.

Ram and try to replace processor

[stj]

Re: lenovo G450 no back light on led screen.

check pin36
it's the signal to turn the led's on.

[rickybucalan]

Re: lenovo G450 no back light on led screen.

check pin36
it's the signal to turn the led's on.

i check with continuity test CN1 pin 36 to JLVDS1 pin 13 its ok. how do i check if it switching on?

[dj_ricoh]

Re: lenovo G450 no back light on led screen.

ok this is simple!
on 24 what connector do you have? 1 or 2?

take a snapshot of the connector and write there every voltage you got on the connector!
with LCD connected ok?
BEWARE! slow and don`t slip the probes.

after we will focus on page 36; just locate it KBC U46

[alihomee]

Re: lenovo G450 no back light on led screen.

there r 3 tyeps of voltages to turn leds on.20v as main voltages 3v for display and 3 v for on off try to short pin 5 and 6 of ur led panal from right side

[rickybucalan]

Re: lenovo G450 no back light on led screen.

ok this is simple!
on 24 what connector do you have? 1 or 2?

take a snapshot of the connector and write there every voltage you got on the connector!
with LCD connected ok?
BEWARE! slow and don`t slip the probes.

after we will focus on page 36; just locate it KBC U46

connector JLVDS1.

here is my voltage reading.

pin pin
1. 20v 2. 3.3v
3. 20v 4. 3.2v
5. 0v 6. 3.2v
7. 3.3v 8. 0v
9. 0v 10. 3.3v
11. 0v 12. 0v
13. 3.1v 14. 0v
15. 0v 16. 1.1v
17. 0v 18. 1.2v
19. 0v 20. 1.3v
21. 0v 22. 1v
23. 0v 24. 1.3v
25. 0v 26. 1v
27. 3.3v 28. 1.2v
29. 3.3v 30. 1.1v

[dspok]

Re: lenovo G450 no back light on led screen.

@rickybucalan
LED voltage is present in LVDS connector.
Check LED fuse in TCON board, sometime it blows up which cause no backlight.

[atsio]

Re: lenovo G450 no back light on led screen.

Problem with SIO. You need to supply 3.3v to pin 9 of lvds connector. Check resistance to ground of that pin. Hopefully problem is C852

[rickybucalan]

Re: lenovo G450 no back light on led screen.

@rickybucalan
LED voltage is present in LVDS connector.
Check LED fuse in TCON board, sometime it blows up which cause no backlight.

i guess its fine. and i already check with another led panel.

[rickybucalan]

Re: lenovo G450 no back light on led screen.

there r 3 tyeps of voltages to turn leds on.20v as main voltages 3v for display and 3 v for on off try to short pin 5 and 6 of ur led panal from right side

i have try your instruction its doesn't work.

[lezsimply]

Re: lenovo G450 no back light on led screen.

check voltage on pin no.105 of SIO page 36. post result

[rickybucalan]

Re: lenovo G450 no back light on led screen.

when i trying to put an external lcd on it doesn't show anything. but when disconnected led cable from mobo its working with external monitor.

[rickybucalan]

Re: lenovo G450 no back light on led screen.

check voltage on pin no.105 of SIO page 36. post result

its 3.3v lezsimply...

[rickybucalan]

Re: lenovo G450 no back light on led screen.

check voltage on pin no.105 of SIO page 36. post result

its 3.3v lezsimply...

[rickybucalan]

Re: lenovo G450 no back light on led screen.

any body could help me.pls.

[lezsimply]

Re: lenovo G450 no back light on led screen.

have you tried different lvds cable?

[dj_ricoh]

Re: lenovo G450 no back light on led screen.

ok!
lets do this!
I`ll help you!
U46 KBC : no voltage on lvds connector on pin INVT_PWM and DAC_BRIG
check on KBC on pin 21 and 68

[dj_ricoh]

Re: lenovo G450 no back light on led screen.

DAC_BRIG needs to be ... I think around 3.1(2)v-3.3v its the adjust voltage. no voltage here no backlight. if you connect 3.3v direct you wont have adjust only full brightness.
and INVT_PWM like the name say Invertor power

[rickybucalan]

Re: lenovo G450 no back light on led screen.

DAC_BRIG needs to be ... I think around 3.1(2)v-3.3v its the adjust voltage. no voltage here no backlight. if you connect 3.3v direct you wont have adjust only full brightness.
and INVT_PWM like the name say Invertor power

tnx for reply. hmmp i got 3.3v on pin 21 of u46 and 0v on pin 68.

is the 3.3v on pin 21 will appear on pin 11 of JLVDS1?