Switch Lite no backlight

[FonzT]

Hi y'all.

I already saw a lot of topics here and there, but I could not figure out what's going on with my Switch Lite.

Basically, there is no backlight, but I can see the screen if I shine a light to it.

I already replaced the ribbon connector and the daughter board itself.

All the buttons and stick work on daughter board.

Continuity is there and I checked my diode readings for the backlight connector:
- starting rom top -> 0.522 - 0.501 - 0.270 - 0 (well, the last pin is the ground)

Here's pics of my Switch Lite:

https://postimg.cc/fSsS15N8
https://postimg.cc/Cn4n0DMS
https://postimg.cc/cgw8D2VK

All seems to be there and nothing looks burned.

I checked for shorts around the inductor, diode and capacitors around the backlight IC on the main board, but I cannot read any short. Diode readings works in one way, as it should.

I just checked for voltage on the second pin of backlight connector and I get 3.4 volts and 3.1ish volts at the top terminal of the cap near the diode, at the top of the inductor.

I think the screen is NOT the culprit.

Backlight IC, diodes and capacitors/inductor do NOT get hot.

Inductor reads less than 1 ohm, so I think it's good.

What do you advice me to check?

There is a method to check the backlight IC?

Can I check the backlight indipendently?

Thanks in advance.

EDIT:

I get 3.3v at VIN pin for TPS61163... is this correct?

EDIT 2:

This is an image of screen back: https://postimg.cc/yk7s7g9L

Does this look like water damage?

 

[HawaiianInTown]

I recall seeing something about the game cart daughter board having an affect on the display? May be an area of the console to inspect?

 

[FonzT]

Hi. Thanks for your reply.
I tried disconnecting the entire game cart board, but nothing changes.
Anyway, I don't think what that board has to do with the backlight.
If it's helpful, I get 3.3v at VIN of the backlight IC... is this correct?

 

[The Real Jdbye]

Hi y'all.

I already saw a lot of topics here and there, but I could not figure out what's going on with my Switch Lite.

Basically, there is no backlight, but I can see the screen if I shine a light to it.

I already replaced the ribbon connector and the daughter board itself.

All the buttons and stick work on daughter board.

Continuity is there and I checked my diode readings for the backlight connector:
- starting rom top -> 0.522 - 0.501 - 0.270 - 0 (well, the last pin is the ground)

Here's pics of my Switch Lite:

https://postimg.cc/fSsS15N8
https://postimg.cc/Cn4n0DMS
https://postimg.cc/cgw8D2VK

All seems to be there and nothing looks burned.

I checked for shorts around the inductor, diode and capacitors around the backlight IC on the main board, but I cannot read any short. Diode readings works in one way, as it should.

I just checked for voltage on the second pin of backlight connector and I get 3.4 volts and 3.1ish volts at the top terminal of the cap near the diode, at the top of the inductor.

I think the screen is NOT the culprit.

Backlight IC, diodes and capacitors/inductor do NOT get hot.

Inductor reads less than 1 ohm, so I think it's good.

What do you advice me to check?

There is a method to check the backlight IC?

Can I check the backlight indipendently?

Thanks in advance.

EDIT:

I get 3.3v at VIN pin for TPS61163... is this correct?

Check for damage to the ribbon cable, especially at the connector end and where it bends. Damage can be hard to spot without a microscope. If there is any corrosion on the pins, clean with IPA and gently scrape off as much corrosion as possible.

 

[FonzT]

Hi. Thanks for your reply.
I already replaced the ribbon cable and the daughter board itself.
All buttons on daughter board are working. It's just the 17v rail which is not 17 volts, but it's around 3.4 volts...
I see NO signs of corrosion.

 

[FonzT]

Hi y'all.
I just checked for voltage among the two feedback pins and high volt rail.
They have almost equal voltage, around 3.4ish volts...
So they are not drawing any current at all?
Because they should have potential different, otherwise no current is drawn.
Right?
Does this indicate fault in screen itself and NOT backlight IC? Or could be the IC anyway? Maybe the Mosfet inside is not operating?

EDIT: This is an image of screen back: https://postimg.cc/yk7s7g9L
Does this look like water damage?

 

[FonzT]

I solved my problem.
It was:
1. burned out wide connector on daughter board
2. burned out FPC cable, around bigger vias (gold turned gray)
3. faulty backlight on LCD itself

 

[thesjaakspoiler]

Glad to hear you fixed it.
Those marks do look like some liquid damage (water/juice/soda).
The whole screen should be about the same color.