Samsung LCD model: (713BM Plus) Not working

[r.raslan]

Hi,
I have LCD Samsung model "713 BM plus" not working.
I opened the monitor to find two boards:
1) Switching mode power supply: (I tested it and It was outputting voltages exactly as it was labeled on the board)

2) CPU board: this board takes the signal from the PC and process it and send it to the LCD panel to be displayed.

Problem Description:
The display is not working (not showing anything)

Any idea?

 

[rmn_tech]

Inverter or backlight

 

[r.raslan]

I have tested the voltage at the terminals of the backlight but there was no voltage using DMM set at 1000 DC range and also tried the AC range.

For the switching mode power supply, the voltages are 15 DC and 5 DC which are correct.

What do you advice me? knowing that there is a power LED should be lighted up (turns ON) when the display turned on, however, it is not lighted up at all.

 

[MrKay]

Just an observation/suggestion. Are the two voltages you mentioned steady or do you note constant, even minor variations. I had a similar situation where the output read ok on a DMM but when checked with an oscilloscope the waveform was distorted indicating a failure in the power supply.

 

[r.raslan]

on DMM the voltage looks steady. I do not have OSC. so how should I know the power supply is well functioned or not?

 

[baklanov_a]

full schematics https://www.electronica-pt.com/inde..._remository/Itemid,34/func,fileinfo/id,20169/

good luck

 

[killivolt]

I've had trouble with the Video Cards and Bad Caps in the Power supplies. If you have a ESR meter you can check them, the ones I've seen bad are 1000uf not alway's bulging but usually are, located on the secondary side of the power supply.

If their good, chances are it's the video card, I don't have a fix for that.


kv