Lg49uj6200ua

[ljintexas]

This set will fire up, complete initial setup screen info, language, country, time zone. when select OK at end of setup goes to blank screen. Upon power up standby LED blinks three times. No response to remote. will not take software update through USB port. I noticed that with set off, all 13.2 volt pins show 12.0 volts. Once fired up shows 13.2 volts on same pins. Electrolytic caps close to the plug all show 12.0 volts in standby. LED Outputs are both 64.75 steady instead of 66 volts. Two main boards exhibit same behavior. A third main board would sometimes go into menu and even display PIP video and sound in menu on input selection screen. When input selected (HDMI) only audio came through, no display on full screen, this board took software update.
Could low voltage on SMPS be causing this behavior? I am stumped. PSON is 0 volts in standby, 1.84 volts when on. label on panel says Skyworth?
TIA

LJ

[nomoresonys]

Re: Lg49uj6200ua

Do you have 5 volt standby voltage on powersupply board?

[nomoresonys]

Re: Lg49uj6200ua

Are you sure that model number is correct?

[nomoresonys]

Re: Lg49uj6200ua

Are you sure that model number is correct?

Found it model number is correct, just wasn't finding anything with the ua suffix.

[ljintexas]

Re: Lg49uj6200ua

I have no 5 volt standby voltage, but I have 12 volts. Standby LED is illuminated in off mode. PSON is at 1.84 volts when set is on. Backlights come up and main LG splash screen and setup function works. But only to set language, country, time zone. Once all are selected and I select OK, no video generated full screen. I get a flash of video like it starts to process then goes to blank screen. Sure acts like a CPU/EPROM issue to me. Anyone know what the three blinks upon power up means?

[ljintexas]

Re: Lg49uj6200ua

Replaced three main electrolytics (1000uf x 25 V) on smps and resoldered every main power passing device I could find. No difference.

[nomoresonys]

Re: Lg49uj6200ua

If you unplug cable from powerboard to mainboard do you have the 5 volt standby on powerboard then?

[nomoresonys]

Re: Lg49uj6200ua

I can't see your board too well, what is the standby voltage reading on cn2? see the map/legend right beside it, it might show the expected voltages?

[nomoresonys]

Re: Lg49uj6200ua

With everything connected, turn on tv check the voltage of the legs of the big capacitors C2 and C3, red lead on positive leg negative lead on negative leg, careful when testing as this is the HOT/DEADLY side of the board.

[ljintexas]

Re: Lg49uj6200ua

381 volts is what I got a few days ago across those caps.

[ljintexas]

Re: Lg49uj6200ua

The fourth picture from the left shows the legend for CN2. INVON is pin 1. I will check voltage in off state on that pin. I know PSON is 1.84 volts when on, 0v when off.

[nomoresonys]

Re: Lg49uj6200ua

Ok, I don't see a standby marked on that legend, yes your ps-on seems low, looking like a problem with mainboard.

[ljintexas]

Re: Lg49uj6200ua

Seems like everything reads a bit lower than should be...381 should be 400, 12 should be 13.2, 1.84 should be 3.3..is this a pattern?

[nomoresonys]

Re: Lg49uj6200ua

Good question, you should probably test the powerboard by itself unhooked from mainboard, I'm not sure how to do it on this set tho.

[budm]

Re: Lg49uj6200ua

PS-ON is find otherwise you will not have that 380VDC PFC Boosted Voltage.
13V is the standby Voltage for this TV..
https://www.badcaps.net/forum/attach...5&d=1543173751
You need to report the Voltages on those pin after the problem occur so we can see what control Voltages are missing.

[ljintexas]

Re: Lg49uj6200ua

Thanks Bud. I will do that and report back.

[ljintexas]

Re: Lg49uj6200ua

--------- Stdby --- On
13.2V -- 12.03 --- 13.25
13.2V -- 12.03 --- 13.25
Gnd -- 0.00 --- 0.00
Gnd -- 0.00 --- 0.00
13.2V -- 12.03 --- 13.25
13.2V -- 12.03 --- 13.25
Gnd -- 0.00--- 0.00
Gnd --- 0.00 --- 0.00
13.2V --- 12.03 --- 13.25
Gnd --- 0.00 --- 0.00
P/ON --- 0.00--- 3.45
Gnd --- 0.00--- 0.00
PDIM --- 0.00--- 3.23
INVON ---- 0.00--- 1.84

PFC Main Caps On are 381V. Stdby they bleed down to 0V but it takes 10 minutes. Crappy Table but readable!

[nomoresonys]

Re: Lg49uj6200ua

Ok, I see P/ON is 3.45, INVON appears to be low on your new readings, thought 381 was good for pfc, are the backlights on?

[budm]

Re: Lg49uj6200ua

"PFC Main Caps On are 381V. Stdby they bleed down to 0V but it takes 10 minutes. "
Are you 100% sure that ist goes down to 0V?
It should go down to around 160VDC when PS-ON is not present, for it to be 0VDC, the AC input to the board has to be 0VAC.
The other Voltages should also be 0V too if the main cap Voltage goes down to 0VDC.
Please up load good clear straight shot of the whole bottom side of the power supply board.
BTW, it looks like LG is now selling rebadged SKYWORTH TV as LG TV, sad.

[ljintexas]

Re: Lg49uj6200ua

You are correct Bud.
They only bleed down to 0 volts with AC disconnected. I will measure what they bleed down to with AC on but I seem to remember it was 165 volts last time I checked it. I will remove smps and get you good clear pics of both sides of the board. Yes, Nomoresonys, backlight comes on with no issues at 64.75 volts for both LED1 and LED2.

Many Thanks!

LJ