Samsung 2253bw black screen

[e3gsr]

Hi guys i have been reading this forum with great interest the last couple of days, The reason I am here is I have a problem with a monitor I was given. The problem is the screen is permanently black, Back lights don't come on at all. I stripped it down and found bad caps so far I have replaced 4x820 1x330 and 2x1000. Lamps have been tested on another good monitor and are all working fine. When plugged in and turned on you can hear a feint squealing from the board but its hard to make out where it is coming from.Now I have 13.4v to my inverters but still no lighty. Anyone any ideas what to go for next before i give it .Apologies if I haven't put enough info if you need to know anything just ask. Forgot to say i am not totally green when it comes to electronics but i am no expert, so please go easy on me and any help to get my monitor working would be much appreciated.

[Rtech]

Re: Samsung 2253bw black screen

Measure the resistance of the Secondaries on the Inverter transformers.

[e3gsr]

Re: Samsung 2253bw black screen

Thanks for the reply much appreciated I have done that and they both read around 1k with a fluke 87v dmm. Any other ideas would love to hear them, Would be great to get to the bottom of this problem.

[selldoor]

Re: Samsung 2253bw black screen

Does it not even flash on for 1 second?
With it all connected and on, test voltages out on power board sockets see if they agree with any board markings for the socket.
Welcome to the forum-
We can sometimes help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

[e3gsr]

Re: Samsung 2253bw black screen

nope doesn't even flash. I will test what i can later and report back and try to take some pics too.

[e3gsr]

Re: Samsung 2253bw black screen

right just had 5 mins so i tested the board voltages. on the connector to the front panel i get
gnd-0v
key 2-1.82v
key 1-1.82v
led ranges from 2.7 to 0v obviously
3.3v-3.3v surprisingly enough

on the 12 pin connector i am getting
1-1.5v
2-14v
3-0v
4-0v
5-5.29v
6-5.29v
7-4.4v with led on
8-0.01 with led off jumps to around 1v when led on hard to measure accurately in time given
9-3.3v with led on drops when led goes off
10-2.7v with led on
11- around 1.8v with led on
12- around 1.8v with led on
does not flash on when turned on at all.
I have 14.9v at F301 and 13.4v at inverter connections not tested output for obvious reasons.
The led on the front panel flashes on and off even when connected to the pc.
I will take pics now and post them up.
Thank you for your help in trying to solve this matter.

[e3gsr]

Re: Samsung 2253bw black screen

pics of boards as requested

[Rtech]

Re: Samsung 2253bw black screen

Although you have given the voltages on the 12 pin connector, you need to qualify them by stating what they are supposed to be....ie what is written on the Board..eg Dim, 5,1 volts. gnd etc etc.

[e3gsr]

Re: Samsung 2253bw black screen

ok sorry here we go
1- b-dim
2- 13v
3- gnd
4- gnd
5- 5.1v
6- 5.1v
7- a-dim
8- on/off
9- 3.3v
10- led
11- key 1
12- key 2

[selldoor]

Re: Samsung 2253bw black screen

Very good pictures -thanks have you tested the small green fuse in the middle of the power supply board.

[e3gsr]

Re: Samsung 2253bw black screen

F301 yes I have its fine.

[selldoor]

Re: Samsung 2253bw black screen

Can you test the voltage at each side of the F301 fuse use a ground screw for the black probe

[budm]

Re: Samsung 2253bw black screen

pin8 is for backlights on/off. 0v = off, I expect it to be >3vdc. It will go high when the monitor is first turn on, it will go low later if it does not detect the video signal from the PC, same thing for the voltage to the T-CON board on the LCD panel. If you remove (do not do it with the connector connected due to output drive may be at logic lo) that connector from the main board and use 1K resistor between pin8 and 5V, that will force the backlights to come on.

"on the 12 pin connector i am getting
1-1.5v
2-14v
3-0v
4-0v
5-5.29v
6-5.29v
7-4.4v with led on
8-0.01 with led off jumps to around 1v when led on hard to measure accurately in time given
9-3.3v with led on drops when led goes off
10-2.7v with led on
11- around 1.8v with led on
12- around 1.8v with led on"

[rogfanther]

Re: Samsung 2253bw black screen

Board IP-49135B, seems I had one of these in a 743-something display.

Just to be sure, you are measuring the voltages with the two boards connected, right ?

[Rtech]

Re: Samsung 2253bw black screen

As suggested Pin 8 switches the Inverter on, and is usually about 3volts Dc from the Logic Board.What you can do is plug in your lamps,switch Power onto the Board leave the logic board not connected and the on off not connected,then apply 3v DC from a Bty between Pin 8 and one of the Ground connections, tha latter being a substitute for the Logic Board 3v, and the Lamps will normally light if all is well with the Power board ??

[e3gsr]

Re: Samsung 2253bw black screen

selldoor the voltage at both sides is a little over 94v is that right?
rogfanther yes all connected up and tested live.
budm and rtech i will try that now and let you know how i get on, That is if i dont end up in casualty lol. In fact I wont try it just yet until someone can confirm the voltage is correct on f301 at 94v.

[rogfanther]

Re: Samsung 2253bw black screen

From your pictures, it should measure about 13-14V, considering that screw hole near the logic board connector.

Possibly your meter was in a wrong scale ? was it in AC maybe ? 94V should have blow the caps in that line.

[selldoor]

Re: Samsung 2253bw black screen

I agree - the caps should be 25v and even upgraded to 35v would still have blown.

[budm]

Re: Samsung 2253bw black screen

Check your Voltmeter aging by measuring know good batteries, that voltage cannot be 94V for the inverter circuits, It should be around 15~20V for 22" Monitor.

[e3gsr]

Re: Samsung 2253bw black screen

oops yes your right again i was on ac doh!
just tested again and it is just over 14v. is there any point on the board i can pick up a 3v supply to feed pin 8 or does it have to be external supply?