Hardware Switch Backlight voltage?

w0nk1 · May 26, 2020

I replaced a broken USB-C port and it is docking fine. But for any reason the backlight isn't turning on.

Then I measured the voltage at the backlight connector of my own switch and get around 14 volts if it's turned on.
The console where I am working on, shows just the standby voltage of around 4 volts.

What I can tell is, that the ribbon cable connector of the LCD seems to be a little bit damaged inside, but the display is working without the backlight (can see it under bright light). Is there any connection between the ribbon cable of the lcd and the backlight functionality?

Any ideas what could be the issue? Thanks for any help!

linkinworm · May 26, 2020

any damage to a ribbon cable = bad times, they are so thin its easy to break them, and impossible to really repair them

w0nk1 · May 26, 2020

linkinworm said:
any damage to a ribbon cable = bad times, they are so thin its easy to break them, and impossible to really repair them

You mean the ribbon cable of the backlight connector? It worked before the usb-c repair. So i don't suspect the ribbon cable.

linkinworm · May 26, 2020

its possible you broke it during the repair , ribbon cables are as easy to rip as paper

w0nk1 · May 26, 2020

linkinworm said:
its possible you broke it during the repair , ribbon cables are as easy to rip as paper

But should't I get the voltage despite of a broken cable at the connector itself?

bombob · May 26, 2020

If the connector is broken and pins are sorted ,you will not get the voltage

Sent from my SM-N960U using Tapatalk

linkinworm · May 26, 2020

maybe the connector is broke on the board? check the pins, and if the switch is smart it wont supply power if nothings connected in order to protect its self from frying stuff

w0nk1 · May 26, 2020

Mhhh I have some irreparable motherboards laying around whre I could salvage the connector from.
Any idea how to proper desolder it?

Ttm3 · May 26, 2020

On something like that I apply hot air from the other side of the board

bombob · May 26, 2020

w0nk1 said:
Mhhh I have some irreparable motherboards laying around whre I could salvage the connector from.
Any idea how to proper desolder it?

Make sure its broken before attempting repair. Use low melt solder and a hot air station.Use kapton tape for the surrounding areas

Sent from my SM-N960U using Tapatalk

w0nk1 · May 26, 2020

I swapped over the cases to confirm damgages and found out, that the repaired motherboard works fine with the other display/backlight.

So I attached the known "good" board in the other case and there is also a backlight issue.

What I've not seen during the previous attempts was, that the backlight lid up for aprox. 1 second and goes out immediately. :-/

--------------------- MERGED ---------------------------

EDIT:
Guys I apologize! It was really the ribbon cable of the backlight which is broken! I could barely see it under the microscope, but it is damaged. I will try to repair it in some kind. Thanks!

Ttm3 · May 26, 2020

I've actually had luck soldering those if it's a small enough break. But you have to be very careful

w0nk1 · May 26, 2020

I was able to scrape some isolation off the cable and could tin it. Afterwards I soldered a piece of 0.15mm wire to it and it works like a charm!

Hardware Switch Backlight voltage?

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