Terra 2450W LCD/LED

[Hauke]

Hello guys,

I have a 24" screen with LED backlight which won't turn on. Even the status LED near the buttons won't light up.

The monitor is powered by an external 12V power supply.
The internal voltage regulators seem to work properly, because I found all needed voltages on the board (12V, 3.3V, 1.8V).

The LED backlight driver board also works right, because I wired a small testing circuit to it and backlight showed up.
I found the schematics of the board online: https://cdn.badcaps-static.com/pdfs/...c2db600ae3.pdf

Here is a picture of the board:



After my testings I think that the "TSUMU58" IC may be dead, because the status LED is directly connected to the pins GPIO_P06 and GPIO_P07.
With your experience, do you think the IC is dead? How would you continue troubleshooting?


Thank you for your answers,
Hauke

[piernov]

Re: Terra 2450W LCD/LED

Do you have 3.3V on the power button? Does it go to 0V when you press it?
All voltages present on U7 (AVDD, VDDC, VDDP)? RST pin high?
+5V present on L1?

[Hauke]

Re: Terra 2450W LCD/LED

Thank you for your answer.

The button pulls 3.3V at GPIO_P14 to low. 5V is also present on the board.

AVDD is 3.3V, VDDP is 3.3V and VDDC is 0V. The RST pin is low.

[Hauke]

Re: Terra 2450W LCD/LED

I got it now! D2 had a loose connection. While pressing against it with the probe of my multimeter voltage was there - otherwise not. I resoldered it and now it works.

[piernov]

Re: Terra 2450W LCD/LED

Makes sense since you had VDDP and not VDDC. U7 could still have been faulty but you were somewhat lucky.
Check the solder on the surrounding caps too (C54/C55). I can't really see but the soldering doesn't look great on the picture.

[Hauke]

Re: Terra 2450W LCD/LED

Ok I will resoluter those capacitors too. Better I do it now than in two weeks..
Thank you for your help, you had the right tip for me.