Panasonic TH-L50B6A

[brooksy05]

So I can confirm its not the A board
All voltages stable from the P board

The output from the Ld board to back light pulse up and down
with or without back light hooked up. I took a plunge and split the screen ( I have done many phones) and all leds look OK.

So now where is the best place to find parts the 2 local shops haven't been to keen to order parts in before for me

[downunder]

So what have you decided, LD board?

Panasonic spares are supplied by Statewide Appliance Spares or JNG. Get the correct part number from the service manual.

[brooksy05]

Yes Ld board, what on the board I don't know.
I wish at time like this I finished my traineeship when I got out of school.

I had the fets off the board and they seem to test OK, so I will try find out a price on a new LD board and see if it's worth the money to fix. It was a free TV, so easy come easy go

[brooksy05]

https://www.google.com.au/url?sa=t&source=web&rct=j&ei=81eiVYjqGsHwmAXj64D4BQ&url=http://www.semicon.sanken-ele.co.jp/sk_content/bl0200c_ds_en.pdf&ved=0CBsQFjAA&usg=AFQjCNHnuK7A-s56rvTMihH5L5zo1eVs4Q
Link to data sheet for the main ic on the LD board

[brooksy05]

What's the chances of the LD board from a tx-l50b6b
Working in this TV?

See attached manual
The P board and LD board schematics look to be the same
And I can get the board cheep from the UK

[downunder]

Didn't have time to study the P-board, but the LD-board look identical circuit-wise. Some difference in the part number but I guess it's for a different market. Worth a shot.

Bruce

[brooksy05]

Well the replacement LD board has been ordered and should be on its way. I will let you know how it goes.

I must say a big thanks to you Bruce for all your help

[downunder]

Another tech having similar problems tells me the LD board is NLA.

Bruce

[brooksy05]

Yeah that's what I found to
I got one from the UK, form the
Tx-l50b6b unit I posted the manual for.
the schematic  all looks the same, photos of the board are the same. Number on the board tnp4g549 the same just different part numbers in the manuals.

So I'm confident it's going to work as it should
Only difference is it has the difference caps that the service bulletin you posted installed already.


But then someone with better knowledge may be able to fix the board

[danyelgeelong]

Hi guys. Sorry to revive an old thread but, I'm having the same issue (flickering backlight) with same model (TH-L50B6A) and need to ask, replacing the LD board fixed the issue? Also is the service manual still available as I cannot see it in the download section. Cheers!

[downunder]

Hi Dan.

I have uploaded the service manual to the download section. Backlight failure seems common on this model - uses a LG panel - but this invariably activates a error code of 1.

Check these voltages on the LD Board for stability. At connector LD1, BL-ON at pin2 and 24V supply at pins 8,9,10. At LD3 (output),
pins 1 and 5 are the LED drive voltages.

A pity brooksy didn't follow up but I have to say my gut feeling is an iffey panel (LEDs).                                Bruce

[danyelgeelong]

Hi Bruce.

Thanks for your prompt reply and also for uploading the service manual again.

I will do as you have mentioned and report back with my findings, only due to work commitments, I wont get a chance to do anything until midweek :(

Regards!

[danyelgeelong]

OK so it wasnt easy testing these voltages on my own because once the TV throws the error (green light goes out, red starts flashing) I have to put the tester down to unplug and plug back in the TV mains every 5 seconds or so. Ive tested the at connector LD1, BL-ON at pin2 (fluctuating between 0 to 3.2V) and 24V supply at pins 8,9,10 (all have 24V +or- <0.5V)  And at LD3 (output), pin 1 (fluctuating between 9 to 14V) and pin 5 (nothing at all).

I've been searching for an unicorns err LD Boards, found one, second hand, selling for more than Id like to spend on S/H. So hoping it may be something else causing this problem.

Next step?, disconnect the BL-ON line, or cut it, and connect it via a 100 ohm resistor to the STB-5V (or 3V3) as a substitute for the BL-ON voltage. Only problem is in the schematics I cannot tell which is the STB-5V (3V3) :(

[downunder]

What about using an external power supply......a couple of 1.5V batteries perhaps. The output at LD3 is definitely screwed up.

[BookWormStud]

Problem may well be A-Board if BL-ON is all over the shop, as that's where the BL-ON is generated.
Can you disconnect the BL-ON line, or cut it, and connect it via a 100 ohm resistor to the STB-5V (or 3V3) as a substitute for the BL-ON voltage. If the backlights come on without flickering, then you'll know the A board is the offender.
You are correct in that the 16V to the LD board is not used.

Bruce

Hi
can you please elaborate this in easy words please.

thanks