w530 backlit keyboard problem

[tsathoggua]

Hey!
I recently became a happy owner of a w530. But since it came with a backlit keyboard, and I wanted it to be backlit, I bought a suitable keyboard.
And despite the fact that the keyboard itself functions well, the backlight function does not work. I tried downgrading the bios, installing the latest version and even the 1vyrain version. Nothing helped, fn+space only turns thinklight on/off.
Thinking that the keyboard itself might be defective, I bought another one of the same type, but it didn't solve the problem either.
I was also advised to check the fuse F23, based on the fact that it is responsible for supplying power to the backlight. I'm not experienced in working with microelectronics, but it's most likely fine (the multimeter beeps happily and the resistance reading is close to zero).
What else can be done to analyze and identify the problem area or to resolve this issue?

PS: the previous owner cannot (or does not want to) answer whether the kbd backlight ever worked at all

PPS: keyboard FRU 04x1240

[RealBlackStuff]

Welcome to the Forum.
Can you check that pin 29 from the keyboard connector connects to Fuse F23?
Maybe there is some dirt or corrosion in that connector?

That KB 04X1240 is indeed a backlit US keyboard, made by Chicony.
Hopefully you did not get a non-backlit Chinese knock-off with false label.
It should have a light symbol on the spacebar, pointing towards the screen.
Press Fn/Spacebar (some models also Esc) together to switch backlight On/Off.
See also this: https://pcsupport.lenovo.com/om/en/prod ... s/ht104656

[Jake.Werecat]

You can also confirm if the keyboard is / is not lit by feeling the keycap with your finger (or looking with you eye).
Backlit kbds have perfectly smooth surface,
non-backlit kbds have a little rough surface - with a delicate pattern that can be seen/felt on top.
Also the letters are different - backlit ones are molded into plastic, non-backlit are just printed on top and protrude slightly.