Lenovo L450 no display , but only VGA

[Rofix]

Hello everyone I have a problem with my Lenovo L450 there is no image on the display, but on an external monitor connected via VGA it works.

Motheboard is : AIVL1 NM-A351 Rev .1 . . LCFC FRU:00HT673

Laptop has no picture and no backlight,but ,the display tested on another PC works

the main voltages are all present on the motherboard connector except the +3VALW which varies as follows:

+3VALW: if the PC is off I find 3.3V when I turn it on they drop to 1.8V

Thanks in advance for all the advice and help

[mon2]

Review the voltage to ground of the EN1 / EN2 pins on PU8. PU8 creates this +3VALW power rail. If working correctly, the schematic states it can output 8A of current.

Test without the display to see if this same power rail drops the voltage when powered on.

[Rofix]

hello thank you
the EN1 / EN2 pins on PU8.
Sorry but which one are you referring to? on the PU8?

[mon2]

See attached.

[Rofix]

Hi, thank you, I couldn't find the PU8 on the diagram I downloaded, I probably downloaded a version that wasn't very compatible

[Rofix]

Hello everyone, I noticed something strange, by disconnecting the display the voltage always remains at 1.8 V, however, by disconnecting the cable from the motherboard the voltage stabilizes at 3.3 V, possible cable problem?

[mon2]

The same display with the same cable works on another laptop that is the same model?

[Rofix]

Hi, thank you for the advice. Unfortunately I can't carry out this test, it was nice so at least I could rule out that it was actually the cable but unfortunately I can't.

[Rofix]

Good morning. Do you know where I can find this cable or one that is compatible

[mon2]

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share your pic of your cable and the laptop with this vendor before purchasing.

[Rofix]

hello ok thank you

[Rofix]

Hi, I ordered the cable, I tried to mount it but the problem persists,

[Rofix]

while I was measuring the voltages on EN1 / EN2 on PU8 unfortunately I think that with the multimeter I must have touched some other component and this damage happened to me, the PD23 component blew which should be a diode in theory, sometimes I do this type of check in the evening when you are tired it is better to avoid. Thanks in advance for any advice

[mon2]

https://www.digikey.ca/en/products/d...7-H3F/10259887

it is a generic diode used to power the nearby IC. See the partial schematic above to review the operation. Diodes will pass the voltage from anode to cathode but block in reverse. Often used to permit multiple outputs or power rails to share the line safely. The highest power rail of this cluster will power the target.

The size of this part is a key criteria; the peak voltage is next and peak current.

[Rofix]

Thank you, I was checking the input voltages on the diode, it shows 0 volts, moreover on PIN 8 of the PU8 I find the ground.