LG 55LW5700 Service Manual

[UND312DOG]

Re: LG 55LW5700 Service Manual

Any ideas?

[UND312DOG]

Re: LG 55LW5700 Service Manual

Hi all,

Bringing up an old topic. I ended up reflowing the main chip on the main board. With success. It lasted for a while and died again. I reflowed it again and it worked.

The problem I'm having now is that FTA is not working. Which is weird since I never touched it. I had a look at the service manual and there's a listed procedure to check to see if there's power to tuner. But the problem is that since my version is a TA not a UE (service manual version) the test point dosent exist on my board.

- check tuner 5v power L2104, 2101.

These values don't exist on this board. Only 2204 and 2201. But I can't find them. Could they be behind the cover on the tuner itself?

It would be good to get it working again. Any ideas?

Cheers.

[rievax_60]

Re: LG 55LW5700 Service Manual

Try to reflow the main processor on the main board may help.

I did just that to a 42lw5700. It is working again for now. It would switch on but the back light wouldn't light up. No sound also.
I wonder what goes wrong?

[Sevenqi]

Re: LG 55LW5700 Service Manual

Try to reflow the main processor on the main board may help.

[thoma]

Re: LG 55LW5700 Service Manual

http://www.ebay.de/itm/LG-Main-Board...item1eb61d9b7a

http://www.servicemanuals.co/lg-55lw5700-training/

[thoma]

Re: LG 55LW5700 Service Manual

Does mainboard or power supply react of heating and freeezing?

https://www.youtube.com/watch?v=kf4-w1Kx9bI

https://www.youtube.com/watch?v=0Z_T_cS_B7g

[Decl]

Re: LG 55LW5700 Service Manual

http://manualsbrain.com/en/manuals/1504343/

[budm]

Re: LG 55LW5700 Service Manual

The main key is that does the INV_CTL change state or not, the out put will normally be HIGH to keep the BL-ON switched transistor ON so the BL-ON signal will be LOW (<1V), for the BL-ON to go HIGH, the INV_CTL must go LOW to turn off the switched Transistor.
Bottom line is that the signal should toggle from HIGH to LOW when power switch is activated.

[spintop]

Re: LG 55LW5700 Service Manual

I just checked leg 10 on ic602 (micom). It is the inv_ctl. Measuring 3.5v. I'm stumped.

When you get time mate have a look at the manual. Thanks a lot for spending the time to help me out. I appreciate it.

I had a look at the diagram u posted.
inv_ctl is coming from micom, from here it goes thru a series of resistors, a transistor, some resistors are optional, some are pull up or down, before the signal goes to the connector P502 on pin18.

u could check on these resistors and transistor, there might be the issue causing the 3.5v to be grounded along the way.

[UND312DOG]

Re: LG 55LW5700 Service Manual

Anyone else else with some ideas? I'm struggling to even find a replacement main board online.

[UND312DOG]

Re: LG 55LW5700 Service Manual

I just checked leg 10 on ic602 (micom). It is the inv_ctl. Measuring 3.5v. I'm stumped.

When you get time mate have a look at the manual. Thanks a lot for spending the time to help me out. I appreciate it.

[budm]

Re: LG 55LW5700 Service Manual

May be something is locking out the processor from sending the BL-ON or the interface device between the BL-ON out put line and the processor has problem.
I did not download and look at the service manual yet.

[UND312DOG]

Re: LG 55LW5700 Service Manual

All the voltages on the OS module opt are measuring correct as per the above diagram.

That being said there must be a faulty capacitor somewhere between pin 18 on p501 and wherever the BL-on goes.

[UND312DOG]

Re: LG 55LW5700 Service Manual

http://imageshack.com/a/img922/575/i7R0aU.jpg

[budm]

Re: LG 55LW5700 Service Manual

OK, that is what we thought, no BL-ON signal.

[UND312DOG]

Re: LG 55LW5700 Service Manual

That's correct. Measuring the voltage from pin 18 = 0.04v when turned on. Dissipating to 0 when tv switched off.

[budm]

Re: LG 55LW5700 Service Manual

Hmm, your diagram shows connector P502 pin 18 on the main board to be the BL-ON (same as INV-ON), and pin 1 is the PS-ON (same as PWR-ON).

[UND312DOG]

Re: LG 55LW5700 Service Manual

http://imageshack.com/a/img924/8876/CXE4cd.jpg

[budm]

Re: LG 55LW5700 Service Manual

Per that same link:
http://alpengeist-tvrepair.blogspot....-clicking.html
P404 pin 8 of the main board, but at this point I am sure it is not being sent from the main board otherwise the backlights would have been on which we already proof that the power supply and the backlights are working.

[UND312DOG]

Re: LG 55LW5700 Service Manual

That's the tricky bit. I'm unsure where abouts on the board that needs to be tested for BL-On. Can't seem to see it in the manual.