LG 42SL80 Not working

[powerflow]

Found an lg42sl80 that was thrown out. I'm trying to learn how to repair modern sets and figured this would be a good way to do it. The set will not power up, it goes through a self check or something, relay clicks on cycles through the LEDs then clicks off again and repeats. At first look I found two shorted power mosfets and a fuse as well as a four bad caps, all parts have been replaced and I've managed to get standby 5v. I've downloaded the service manual and tried the procedure to power up the power supply, but no luck the 12v and 24v should come on but they do not.Readings on conector p201 are

Pin1 n/c Pin2 0 to 4.9v
Pin3 - 6 Gnd Pin7 - 10 5.0 to 5.1v
Pin11 - 12 Gnd Pin13 - 14 0v
Pin15 - 16 Gnd Pin17 - 18 0v
Pin19 n/c Pin20 0v
Pin21 .2v Pin22 0.7 to 3.0v
Pin23 n/c Pin24 0v

Been trying to figure it out for some time now, could really use some help.

[budm]

Re: LG 42SL80 Not working

Pictures of the whole back side of the TV so we can see how all the boards are connected together.
No pin names for those pins?
Also need good clear well focused straight shot pictures of the WHOLE boards and around the connectors.
if you look at your pictures you took and cannot read the label, connector names, etc. then we cannot read them either.

[powerflow]

Re: LG 42SL80 Not working

ok I've taken additional pics hope they are better.

[dick_barton]

Re: LG 42SL80 Not working

Have you carried out the tests as shown on page 33 to check the 12V & 24V lines are working?

[powerflow]

Re: LG 42SL80 Not working

yes, but i get no 12v or 24v. I do not know where to go from here.

[dick_barton]

Re: LG 42SL80 Not working

The pdf says that you must use a load (12V bulb in this case) as well as the resistors to power up the supply.
Without the 12V bulb as a load the supplies will not power up.
Please can you confirm once again that you have carried out the tests exactly as shown on pages 32/33. This is important.

[powerflow]

Re: LG 42SL80 Not working

Yes I have done this procedure. I can confirm that the relay does click on when I run this test and stays on. However no other voltage is present (i.e. 12v or 24v) as the service manuals procedure indicates should be. So I'm pretty sure the problem is the power supply.

[ReeceyBurger123]

Re: LG 42SL80 Not working

Your on the right track. Is the a CCFL Lcd set btw not Led backlight ? Also on the psu have you checked the voltage across the bulk Pfc caps ?

[powerflow]

Re: LG 42SL80 Not working

not sure what PFc caps are, but if your referring to the six long brown electrolytics, yes I have check the voltage across them and it is 387v steady.

[budm]

Re: LG 42SL80 Not working

PFC Voltage booster is working.

[dick_barton]

Re: LG 42SL80 Not working

There are several fusable reisitors on that board prefix FR which I would check out with my meter.

[powerflow]

Re: LG 42SL80 Not working

After a short vacation I was able to clear my head and managed to repair this TV. Upon rechecking the board I realized that the voltages were not correct at the high voltage resonant controller ST-L6599, I ordered a replacement from Digikey which arrived earlier today, I replaced it and the set is now working perfectly. Another TV saved from the trash bin.