Samsung 245B 00173A No power No blue LED

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

It looks like the ic is trying to start, Are you getting any voltage on the S_B5V line?
A couple things to check would be CB872 (22uf/50v) CB810 (1uf/50v) or maybe the 5 volt filter, cb876 or cb809.
Most likely would be cb872

I am getting only 1.32Vdc on S_B 5V line

I checked the listed components on board not desoldered
CB872 = 20.4uF
CB810 = 1.2nF (not sure if it is too low for my tester but that is the reading i am getting)

Could the 1uF capacitor be the problem?

CB876 and CB809 are brand new replacements.
CB876 =2680uF
CB809 =2700uF

I am guessing it is because they are connected in parallel that is why the value is approximately the sum of their values.

[redwire]

Re: Samsung 245B 00173A No power No blue LED

I wonder if there is an overload on the second aux. winding for the PFC, whereby ICB801S powers ICP801S (why is every part called 801S...)

I would lift one leg of diode DB803, which disconnects that portion from powering ICP801S. See if the +5VSB comes up.

You have CB872, CB876 OK which are caps that usually causes troubles.

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

I wonder if there is an overload on the second aux. winding for the PFC, whereby ICB801S powers ICP801S (why is every part called 801S...)

I would lift one leg of diode DB803, which disconnects that portion from powering ICP801S. See if the +5VSB comes up.

You have CB872, CB876 OK which are caps that usually causes troubles.

Thanks redwire.
I desoldered one of the diode (DB803) pins and measure the voltage at S_B using LUG1 as ground (or do I need a hot ground for this measurement?). This time the voltage was 2.83Vdc.

Is this a postive sign?
What else would you recommend?

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

Just an update. I replaced CB872 and CB810 and now I have power. The led turns on when pressed.
But display I get is a bright white screen that stays on. Does not recognized any input (picture attached).

Any ideas where to look or what could be my issue(s).

Thanks for all the help so far.

Cheers

[R_J]

Re: Samsung 245B 00173A No power No blue LED

Do you have the +5volts going to the main board (this is seperate from the standby +5.3 volts)
Check that the lvds cable is connected properly to the panel

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

How do I test the 5V? With everything completely assembled and power on (both power board switch and monitor switch)?

The LCD cable is properly connected . I made sure it is fully seated

[R_J]

Re: Samsung 245B 00173A No power No blue LED

How do I test the 5V? With everything completely assembled and power on (both power board switch and monitor switch)?

The LCD cable is properly connected . I made sure it is fully seated

I may be misreading this but, you check for 5 volts with your meter, on the mainboard, it should be marked. and yes with the monitor turned on, if its off you will get no 24 or 5 volts.

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

I may be misreading this but, you check for 5 volts with your meter, on the mainboard, it should be marked. and yes with the monitor turned on, if its off you will get no 24 or 5 volts.

I checked the voltage on CN801 connector and I get 5.3Vdc on the 3 pins labeled as such. I couldn't find the 5V connector or where to measure it. I followed the CN801 connector to the "logic board" and measured the voltage on the pins labeled 5V and all three had 5.3V.

I hope I did the right reading as requested. If not please point me in the right direction (say with a number on the board).

Thanks for all the help and input

Cheers!!

[budm]

Re: Samsung 245B 00173A No power No blue LED

Did you check or re-seat LVDS cable (the cable between the main logic board and the panel) as suggested?

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

Did you check or re-seat LVDS cable (the cable between the main logic board and the panel) as suggested?

Yes I did check the cable and I couldn't find anything out of place. All the wires at least the ones that are visible look intact on both ends. I also made sure they are properly seated.

[R_J]

Re: Samsung 245B 00173A No power No blue LED

Does the power button have any effect, does the monitor turn on and off or does it just give the white screen when first pluged in?
I'm not 100% but FG710 could be a fuse, is it good, It should supply +5 volts to the t-con/panel board
Check the voltage on IC705, pin1 is 5v in, pin2 is 3.3v out, this supplies the micro etc.

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

Does the power button have any effect, does the monitor turn on and off or does it just give the white screen when first pluged in?
I'm not 100% but FG710 could be a fuse, is it good, It should supply +5 volts to the t-con/panel board

The power button does turns the monitor on and off.
At this point I am thinking it may be a problem with either the logic board or the LCD panel itself. I swapped the power supply board for second monitor (I have two of these monitors) and it worked perfectly fine.
So thanks to your guidance I was able to fix the power supply board.

I am not sure what's the next steps to troubleshoot in order to solve the current issue of white screen.

[R_J]

Re: Samsung 245B 00173A No power No blue LED

If the power button is working, the micro is working, What voltage do you have on pin 29 of the lvds cable? Should be +5volts

Try the logic board in the other monitor, no point in trouble shooting it if its working. If the fault is on the board then we can continue.

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

If the power button is working, the micro is working, What voltage do you have on pin 29 of the lvds cable? Should be +5volts

i Try the logic board in the other monitor, no point in trouble shooting it if its working. If the fault is on the board then we can continue.

I transferred all the boards (power supply, main logic board, and another small board, which connects to the LCD ribbon) as well as the LVDS cable from the working monitor.
I still have the same white screen issue. So at this point I guess the monitor is toast, since it is definitely the LCD panel. Unless there is something else I do not know about.

Thanks a million for all the help and input.

[mitchw]

Re: Samsung 245B 00173A No power No blue LED

I once had a similar problem. I checked the PCB on the LCD itself, especially the input fuses, resistors and chokes.
Turned out I was lucky, one of the 0 ohm resistors feeding the +VSB was blown. I also found a short on that line, it was one of the ceramic capacitors that shorted, luckily only a bypass cap. Removed the cap, installed a generic 10nF there, replaced the 0 ohm resistor and voila, it still works today

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

I once had a similar problem. I checked the PCB on the LCD itself, especially the input fuses, resistors and chokes.
Turned out I was lucky, one of the 0 ohm resistors feeding the +VSB was blown. I also found a short on that line, it was one of the ceramic capacitors that shorted, luckily only a bypass cap. Removed the cap, installed a generic 10nF there, replaced the 0 ohm resistor and voila, it still works today

Thanks mitchw.
Which PCB are you talking about? Do you have pictures you can share?
I had given up on the monitor but at this point it wouldn't hurt to try anything since the worse that can happen is it will not work.

Cheers!

[momaka]

Re: Samsung 245B 00173A No power No blue LED

Thanks mitchw.
Which PCB are you talking about? Do you have pictures you can share?

That would be the T-con board - i.e. the small long board attached to the TFT panel typically located at the top of the monitor (under a metal shield).

White screen issue is typically blown fuse and/or other parts on that board. Fixed a few like that - mostly due to shorted multi-layer ceramic caps (MLCCs).

Post some high-resolution images of your T-con board, and we should be able to help troubleshoot the issue. Typically the T-con board has several voltage rails like VDD/VCC, AVDD, VHG, VGL, VCOM, and etc... though the names might vary on some boards. But when a MLCC shorts on one of these rails (most common issue), you get a white screen. Occasionally, the fuse just blows for no reason, but I find that uncommon. The gamma IC(s) can go bad too.

Here's also some details in this thread regarding T-con rails:
https://www.badcaps.net/forum/showth...ght=t-con+avdd

[budm]

Re: Samsung 245B 00173A No power No blue LED

This is where pictures that show all the boards and how they are connected together come in handy.

[redoxy]

Re: Samsung 245B 00173A No power No blue LED

That would be the T-con board - i.e. the small long board attached to the TFT panel typically located at the top of the monitor (under a metal shield).

Post some high-resolution images of your T-con board, and we should be able to help troubleshoot the issue.

Thanks momaka and budm.

I tired taking pictures but due to the nature of the board it was really hard to get a decent full size image. i tried taking small sections at a time so it is a bit clearer. Hopefully there is enough detail to point me in the right direction. If not and anyone has any ideas or tricks as to how to take a good full size picture please let me know.

Cheers!!

[budm]

Re: Samsung 245B 00173A No power No blue LED

Where are the pictures of the whole back side of the monitor showing all the boards I requested?