LG 55LV5500-UA no picture or sound

[dick_barton]

Re: LG 55LV5500-UA no picture or sound

Looks like some sort of feedback error signal to the main IC is keeping the backlights off.

[budm]

Re: LG 55LV5500-UA no picture or sound

Something just will not let me give up on this TV yet. I followed the jumper instructions on how to get the backlights to turn on. They and thier voltages are correct. They stay on as long as I have the set on.

Now... I just using that as a starting point. The circuit never fires up the backlights. If the test has me jumper 3.5 volts to the pin 18.... then pin 18 (as shown in this drawing) should have about that 3.5 voltage for a normal running situation. This drawing taken from the training manual shows 3.28 volts should be present there on pin 18.
My board only shows .034 on pin 18 when hooked up regular ( not jumpered). Please take a look at my notes on the drawing for that circuit. They dont seem right at all but where do I look next? I would assume taht IC602 is putting out the right voltage on that pin 10 (3.5) and then is Q504 isnt doing it's job? One thing that I didnt check is for the emmitter to be properly grounded as shown in the drawing. I dont know if that would cause it to be in the state that it is or not. My transistor theory is kinda rusty at this point.

Can you please upload the PDF of this training manual?

[drkthundr]

Re: LG 55LV5500-UA no picture or sound

I think the training manual he is talking about is this page.

[drkthundr]

Re: LG 55LV5500-UA no picture or sound

I'm having the same issue different model.
https://www.badcaps.net/forum/showthread.php?t=55572

[Dgtech]

Re: LG 55LV5500-UA no picture or sound

Here are both the SERVICE MANUAL and the TRAINING MANUAL. Very similar models that use the same boards with the same part numbers and pinouts.