T240 Monitor Backlighting Issue

[johanneszab]

Re: T240 Monitor Backlighting Issue

I also wanted to say thanks for the contribution to this thread. It saved my T240HD which suffered on the TSTB symptoms. I've changed this capacitor and now it works like on its first day:
http://www.jzab.de/stuff/t240hd/kapu...ator_small.jpg

One different thing I wanted to ask is, what do you think of these wired substances on the other, system PCB i've noticed:
I've taken two images:
http://www.jzab.de/stuff/t240hd/board/board.jpg

Here on the left edge, it looks like the board corrodes and on the whole board surface, there is a sticky, orange fluid on it, looks like coke :P. I wonder where this comes from, and if i should remove it? I certainly never spilled any liquid over my TFT and because of the large amount, i think it was in there right from the beginning. It's only on that board, not on the other one though. The TFT is already 5 years old and worked till last week, so i though ignore the substances on it.

Here is an other picture: http://www.jzab.de/stuff/t240hd/board/board2.jpg

What do you think is that, just out of curiosity?

[g40rocket]

Re: T240 Monitor Backlighting Issue

Hey fellows,

Sorry the delay.

I finally discovered my problem, it was the bulb, check the photo:





Is there any way to get this replacements or i have to buy a new backlight or panel ?

Thanks in advanced.

[g40rocket]

Re: T240 Monitor Backlighting Issue

A little update, i finally purchased my new CCFL tubes from http://www.ccflwarehouse.com


The Samsung T240HD is already in good working order.

Thanks to all that help me in this forum.

With 38 usd (including shipping) i fixed my LCD again !

[AndrakondrA]

Re: T240 Monitor Backlighting Issue

Hello,

After TSTB syndrome, replaced capacitors, ccfl lamps, (transformer (0.9K 1.0K secondary), still have a problem...
I decided to convert my LCD to LED, so want to disconnect the high voltage part of the board (don't want this part to consume electricity)

Questions:
-Can I totally disconnect high voltage part of the board and how?
- Is there any possibility to use monitor power supply to get 12v for the leds or must use independent power supply with independent switch?

Thanks in advance!

[amt]

Re: T240 Monitor Backlighting Issue

Well Mine is fixed! I was on it the other day and one corner went black then with in 1 minute the hole thing was black. I could see that there was something on the screen but it was black. I opened the case and found a resistor with the board burnt around it, the inverter with a small melted spot on the top and the board burnt and the board starting to burn by the transistor on the back. I took off the inverter and could not find anywhere I could get a measurement and tried to open the case to see the connections inside. Luckily I wrote down the number first as it just kind of fell apart under force. I replaced it and bought caps for the ones next to it as I was sure they got pretty hot. They must of been cheap caps (the new ones)as they measured 950 each where the old ones were 820 and that is what they measured (No esr meter). Like I said, I replaced the inverter and the 2 caps and all is well again. Thanks for all of you that input into this topic as it let me learn how to fix this.
Thanks again.

[lizzrd]

Re: T240 Monitor Backlighting Issue

After reading about the OP first post about screen blacking out, and disassembling, seems my board is a bit different. I am looking to check the transformer as shown in reply #4+5.
Any help on what solder points to check for resistance would be greatly appreciated...

[selldoor]

Re: T240 Monitor Backlighting Issue

We prefer pictures to be posted using manage attachments so they remain on the thread
can you edit your post to remove and re attach

[lizzrd]

Re: T240 Monitor Backlighting Issue

sorry for that... i do not have a edit option.

[budm]

Re: T240 Monitor Backlighting Issue

1 & 2, 3 & 4.
BTW, the solder joints of the transformer legs do not look good, You my want to inspect the whole board.

[lizzrd]

Re: T240 Monitor Backlighting Issue

I am a total beginner. 1+2 , 3+4 is what i thought was to be checked. But the board being different puzzled me, still does. Why would they be different ? Would you tell me what looks bad about those 4 points ? I only have a multi-meter, how/what could i check for the whole board ? I could take this board to a PC repair place that did some solder work for me last month if i am not 'able' to. sorry for all the questions...

[budm]

Re: T240 Monitor Backlighting Issue

Oops, set your meter to 2K Ohm scale and take the reading between pin 1 and 2, then pin 3 and 4. NO POWER to the unit of course. The solder joints look like they have some ring (hair line crack) around the pins.
For examples:
http://s807.photobucket.com/user/bud...?sort=3&page=1

[lizzrd]

Re: T240 Monitor Backlighting Issue

so the black to pin 1 and red to pin 2 , shows it reading up to 1. and the same for 3+4...
i also looked at the solder with a mag glass and they seem ok , like the other solder points.
I do not see any discolored points or bad caps.

[budm]

Re: T240 Monitor Backlighting Issue

What scale do you set the Meter's Ohm mode to, 2K?

[lizzrd]

Re: T240 Monitor Backlighting Issue

yes , sorry for the timing of my posts , i have 3 kids here, so kept busy...

[budm]

Re: T240 Monitor Backlighting Issue

Can you post the pictures of the top side of the board and the P/N as printed on the transformer so we can look for the pin out of the transformer?

[lizzrd]

Re: T240 Monitor Backlighting Issue

thanks for your reply Bud,

[selldoor]

Re: T240 Monitor Backlighting Issue

Try the test again resistance should be around 1000ohms
Check you have the meter selector in the correct position - it goes all the way round on mine so
200ohms look pretty much the same as VAC600

Also try scratching the top of the solder joint with the probe

[budm]

Re: T240 Monitor Backlighting Issue

The pin out of the windings in my post 49 is correct, so you may have to clean of the flux or resolder the pins of the transformer and try reading the resistance again.
It has the same pin out as this one:
http://s807.photobucket.com/user/bud...tml?sort=3&o=3

[lizzrd]

Re: T240 Monitor Backlighting Issue

I scraped on the side of the pins and kind of pushed the points of the probes in a bit.
Got readings of 1.006 and 1.012. Don't know if it matters, this board is disconnected from the other board of the unit.

[budm]

Re: T240 Monitor Backlighting Issue

1.006 K ohms, and 1012 K Ohms? If they are, then they are good.