Help with Toshiba 50L2300U

[2many]

Hi, Need help on a 50" Toshiba L2300U series LED TV. Less than 3 years old and the LED back light just went out. Has sound and picture (with a flashlight). I got the front bezel and back panel off (what a pain!). I poked around the power supply board near the LED power connector with an ohmmeter and found 2 shorted Schottky barrier diodes and a shorted N channel Mosfet (I have some experience in electronic circuitry but not with LED TV's). I could not get the exact p/n replacements but replaced them with components that are higher spec in volts and current.

Unfortunately, I did not take any voltage measurements before I replaced the 3 bad components. After plugging in the power supply board, the unit would not power up with the remote or the power button on the main board. I took power supply voltage readings at the connector and they are as shown below. I am not sure what to do next to get the TV to power on to see if replacing those 3 parts helped. When the front bezel was pryed off, the IR sensor and LED indicator connector just ripped off. It does not look damaged. I have not tested continuity of the wires at the IR sensor or LED indicator but will do so. Any help appreciated.




This is the power supply board. The 2 bad Schottky barrier diodes were SR3150 and replaced with 2 dual diodes MUR3020PT (use 1/2 of each). The N Mosfet was PO920ATF and replaced with IRF640

[budm]

Re: Help with Toshiba 50L2300U

Can we see the straight shot pictures of the whole power supply/LED driver board?
I also need the P/N as printed on the BARCODE stickers.

[chrismurphy]

Re: Help with Toshiba 50L2300U

Schottky barrier diodes cannot be replaced with the ultrafast diodes you put in
you need to replace the diodes with the correct ones .The FET should be ok

[2many]

Re: Help with Toshiba 50L2300U

Here's pic of entire board after removal of the 2 didoes and FET (middle one bottom of pic). I'll get numbers on the stckers later.

[2many]

Re: Help with Toshiba 50L2300U

Stickers

B178-B01 C52 REV.C 20 00014 19296 02366


03-PK101W01001-VDAFL-C50-5100-100

[2many]

Re: Help with Toshiba 50L2300U

Schottky barrier diodes cannot be replaced with the ultrafast diodes you put in
you need to replace the diodes with the correct ones .The FET should be ok

Thanks for that info. I have these http://www.ebay.com/itm/361553588394...%3AMEBIDX%3AIT coming in the mail. They are higher voltage and current. Will these be ok?

Do you think having the ultra fast diodes in there have anything to do with not being able to power on the TV?

[2many]

Re: Help with Toshiba 50L2300U

Here's a clearer pic of the board as it stands

[whiz62]

Re: Help with Toshiba 50L2300U

Hello 2many. Hope you get it going. If you need any boards I have a new TV with cracked screen that I got from a dealer. It will fire up. Been sitting in garage for couple of years. Got too many and need to start cleaning out.

[2many]

Re: Help with Toshiba 50L2300U

You have the exact same set? I'll keep you in mind if I can't fix it.

[2many]

Re: Help with Toshiba 50L2300U

Where can I get a schematic/ service manual for my Toshiba 50L2300U? I searched these 2 resources from LongJohns but could not find my TV

http://www.electronica-pt.com/index....,select/id,13/

or

http://www.eserviceinfo.com/

[whiz62]

Re: Help with Toshiba 50L2300U

Yes 2many. It is the same model #. Just let me know if you need anything.

[Moreno83]

Re: Help with Toshiba 50L2300U

Try toms-service-manuals.com for service manuals.

[2many]

Re: Help with Toshiba 50L2300U

The SR5200 Schottky diodes arrived this afternoon from China. I replaced the 2 ultra fast diodes with them but it didn't help, still won't power up.
Can't believe it was powering up and had sound before I did work on the power supply board, afterward that it wouldn't power up no more!

What do the voltage readings above indicate?

I can really use some help or a service manual / schematic.

[dick_barton]

Re: Help with Toshiba 50L2300U

Start from the beginning. With the mainboard disconnected what voltages do you have on the power supply as listed in Post #1

[Moreno83]

Re: Help with Toshiba 50L2300U

Toms service manuals.com and elektrotanya don't have the service manual but i did found this. Its the 32" model but that will be the same i think.

http://electronicshelponline.blogspo...0-led-lcd.html

Hope this helps you a bit buddy

[Moreno83]

Re: Help with Toshiba 50L2300U

The picture of the PS is different but basics will be the same. Strange the power supply does not work anymore after working on it. you did not bend the board? Maybe bad solder joints somewhere?

[2many]

Re: Help with Toshiba 50L2300U

Start from the beginning. With the mainboard disconnected what voltages do you have on the power supply as listed in Post #1

OK. With main board disconnected, pins 10 & 14 = 5.1 V, all other pins = 0 V

[2many]

Re: Help with Toshiba 50L2300U

The picture of the PS is different but basics will be the same. Strange the power supply does not work anymore after working on it. you did not bend the board? Maybe bad solder joints somewhere?

That is not correct. The TV was powering up with the remote and had sound but no backlight (no picture unless I shine a flashlight on the screen). After I replaced 2 diodes and a FET on the LED power section, it stopped powering up.

I buzzed out the IR board and LED indcator connector harness to the main board and there was good continuity on all wires. I thought I may have broke some of those wires during front bezel removal but they are fine.

[Moreno83]

Re: Help with Toshiba 50L2300U

Ok just looking at your last comment makes me think the power supply was good but you have bad leds. As they most of the times are in series , if 1 dies the rest won't work anymore....

Now i understand why you want to turn on the leds in the other thread to see if they are ok. Well i would just remove the panel tbh.

Its not that hard and if you tape the small tabbond prints to the panel nothing can go wrong if you are gentle.
The plastic underneath the lcd is easy to remove and you will get easy acces to the leds.

[2many]

Re: Help with Toshiba 50L2300U

Moreno83, please read the first post in this thread. It gives a history of what transpired.