Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

[bl4ck]

Hi there, after checking other topics without solution to my issue I decided to open this thread asking for your kind help.
As I wrote in the title, my Samsung monitor silently stopped working by turning totally off while I was using it with my pc.

Fortunately, even I'm still a newbie in electronics, time ago I purchased a multimeter and so I've dissembled the monitor and got out the PSU:
http://puu.sh/INodf/f2fe430b5c.jpg


What I have tested/checked so far:
fuse is fine, with cable to main disconnected the LED's doesn't come on.
no visible burnt or blown caps or other components (it seems just dirt on the center).
The integrated STR W6053S does not seem to give a short circuit between pin 1 and pin 3.
Diode bridge does not seem short.

Only thing I've notice is that the top left capacitor 50V CM852 seems just a little bit popped out and as a newbie with a simple multimeter I can say if it's really broken or not. Another thing is that when I did the continuity test on the diodes, the 2 bigger on the right DM852 and DM853 (I've circled them on the attached image) seems to be in short circuit.
What would you do? Do I have to change all these 3 parts (Capacitor and 2 diods) or maybe it's just the capacitor that make those diods short circuit? What test I still do? (always taking in mind that I'm still at the beginning in this field )

[R_J]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

The capacitor is bad but won't shut down the power supply, you will need to remove the diode to check them properly but if they check shorted in circuit one is likely bad

[bl4ck]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

yeah, I'll desolder them for sure.
Today I tried to measure the voltage of 5v and 13v to the Mainboard but instead of null or a fixed value I get random numbers.. Is that mean there's also something else not working properly? or it's just the consequences of the bad capacitor?

Btw someone has found the diagram of this PSU? cause can't find this exact model

[dskall]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

Did you check the diodes?

[bl4ck]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

Did you check the diodes?

Yes, as i wrote in my first post, TWO of them resulted short circuit, I've circled them in the picture in that attachment.
Now I wanted to order them, along the capacitor but it's not easy to read the type are they and I want to avoid ordering the wrong one..
So has anyone the DIAGRAM of this exact board?

[ReeceyBurger123]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

I’ve had shorted sb6100 and uf5402 diodes on this unit check for shorts.

[R_J]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

yeah, I'll desolder them for sure.
Today I tried to measure the voltage of 5v and 13v to the Mainboard but instead of null or a fixed value I get random numbers.. Is that mean there's also something else not working properly? or it's just the consequences of the bad capacitor?

Btw someone has found the diagram of this PSU? cause can't find this exact model

If you have not replace the bad parts yet, what do you expect?

What are the numbers printed on the diodes?

[bl4ck]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

If you have not replace the bad parts yet, what do you expect?

You're right, but I did that voltage too just to make some other test before to order some component, wait days and later discover that I've to order and wait others days till they arrive.. anyway as I said i have some difficulty to read some type of components and can't find the exact schematic file, if anyone have it would be great

[bl4ck]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

I've had shorted sb6100 and uf5402 diodes on this unit check for shorts.

Please l, as I can't find exactly those numbers, can you circle them on the picture posted on my first post? Thank you!

[rddube]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

Yes, as i wrote in my first post, TWO of them resulted short circuit, I've circled them in the picture in that attachment.
Now I wanted to order them, along the capacitor but it's not easy to read the type are they and I want to avoid ordering the wrong one..
So has anyone the DIAGRAM of this exact board?

What we were asking you is to check the diodes out of circuit, just desolder one side and lift it - put your meter in diode mode and check if they block voltage one side and turn your probes around and check if they allow voltage the other side. Report back.

[bl4ck]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

What we were asking you is to check the diodes out of circuit, just desolder one side and lift it - put your meter in diode mode and check if they block voltage one side and turn your probes around and check if they allow voltage the other side. Report back.

Today I've finally got some time and I've done what you were asking me guys. So I've desoldered one side and I've found that one of those 2 was a short circuit. In meantime, I also received the replacement of them and a new capacitor. So I've replaced the single shorted diode and the capacitor. All gone fine apart ONE single issue: when I finished soldering the capacitor and I wanted to cut the exceeded length by mistake I took out of its place a side from the PCB as you can see from the attachment..

I think I've to build manually a link.. but where?

[dskall]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

Except for soldering I'm not sure anything is bad there.

[vinceroger69]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

looks like part of the pcb trace has torn of the board thats around the capacitor leg.

[bl4ck]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

Here you can see it better (in attachment)

[R_J]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

Just bend the capacitor lead towards the solder point (the arrow goes through it) and solder it there, if the lead is too short use a scrap of wire and wrap it around the cap lead and solder it then solder the other end to that pad. Or scrape a bit of the green paint from the trace next to the cap lead to expose some copper trace and the cap lead to it.

[bl4ck]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

Thank you very much for the detailed reply so I haven't to do many question, but excuse me just a little one, about the wire ☺️ It does makes difference if I use one previously cutted from a vcc/gnd of an old general usb cable or if I use a wire from an ac plug?
And one last thing, about where to solder, for me would much easier to link and solder it directly to the solder point (under my red arrow) instead of scraping the green paint, is this last way (scrap paint pad) better in terms of quality?

[R_J]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

You need to connect the positive lead of the capacitor to the trace, how you do it is up to you, I gave you a couple options. I suggested using a piece of wire only if the positive lead from the capacitor would be too short to reach that solder pad.

[nomoresonys]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

one video there, many more if needed: https://www.youtube.com/watch?v=ztuosZQVDFU

[bl4ck]

Re: Samsung LT24C300EW BN44-00505A (PD23A0Q) Won't Turn On (No Standby Light)

In the end it was easier to do it than to say it, and it also came out just like the factory.. ok I'm not so sure about that last thing but it worked great giving me continuity from the capacitor pin to the entire pad with the tester.

After that I quickly did the backlight test (by giving power and leaving the main board unlinked) that this time powered on, and secondly I checked the voltage which gave me a stable 5v and 12v.
So when finally I plugged everything together, the monitor back to work!! http://puu.sh/IPgj5/ef3d89c9f3.jpg

What can I say guys, thank you immensely for giving me support for the various steps! I leave attached how I solved this last hiccup but the main issue was "simply" the bad capacitor a little bit popped and one diode that was giving short circuit. So I hope it can be useful so I can reciprocate help someone else in my same situation 😊