LG 50py2dr Troubleshooting help

[troxel]

I got a LG 50py2dr and just started to look at it. I took my chance and got it off of CL with some other tvs. I am fairly good with electronics and soldering, but really haven't done much with tvs.

When I plugged the tv in, the orange light blinks 15 times then goes to a solid orange. LED 170, 901 and 302 all turn on immediately. I noticed the LED 301 doesn't turn on. There is no picture on the screen. Previous owner also included an extra y-sus board that he said didn't change anything. He said he couldn't remember what was wrong with the tv, but said the board made no change.

Can someone help me with troubleshooting this tv. I can include photos or anything else if needed.

Thanks!

[tom66]

Re: LG 50py2dr Troubleshooting help

OK, top left of this board:
https://www.badcaps.net/forum/attach...7&d=1359929387

See the large connector on the PSU?

Test the voltage on each pin, with all boards disconnected, with the Y-sustain disconnected and with the Z-sustain disconnected.

[troxel]

Re: LG 50py2dr Troubleshooting help

Tested voltages then disconnected the y and z sus and getting zero volts on Va and Vs on all readings. Tested continuity between ground and Va and Vs and it buzzed.

Does that indicated the power supply is not working and there is a short somewhere?

The fused tested good and just visual looked over the caps, which also looked good. I haven't pulled the board out yet to test ESR or other components.

[tom66]

Re: LG 50py2dr Troubleshooting help

Hold the meter in the continuity range across Vs/Va -- may take some time for the caps on PSU to charge up, does not indicate fault. If it stops beeping no short on PSU, have a look at main board and see if it is sending power on signal.

[troxel]

Re: LG 50py2dr Troubleshooting help

Thank you for your help. Definitely appreciate it.

You were correct on the Vs/Va. There is no continuity between the two. Hate to ask, but how do I see it its sending a power signal? Just not sure on all the abbreviation and such.

[tom66]

Re: LG 50py2dr Troubleshooting help

On one of the many connectors going to the video board (has AV inputs on it) there will be a pin marked VS ON.

[troxel]

Re: LG 50py2dr Troubleshooting help

Thanks again. I measured VS_ON and it's zero volts.

[tom66]

Re: LG 50py2dr Troubleshooting help

So main board isn't turning on PDP. Check AC DET.

[troxel]

Re: LG 50py2dr Troubleshooting help

My guess is that is the same as AC_ON? If so, it was 4.29 Vdc.

[tom66]

Re: LG 50py2dr Troubleshooting help

When you press the power button, what happens -- make a note of any relay clicks and changes in VSON.

[troxel]

Re: LG 50py2dr Troubleshooting help

I hear one click and the VS_ON is virtually zero. It something like 5 mV and changes to 9mV. When I turn the TV off, it makes the same one click sound.

[tom66]

Re: LG 50py2dr Troubleshooting help

So, the main board isn't turning on the VS voltage, the fault is probably with the main board.

[troxel]

Re: LG 50py2dr Troubleshooting help

At this point, what would you recommend? Just replacing the main board or is it possible to troubleshoot it?

Thanks for all the help.

[tom66]

Re: LG 50py2dr Troubleshooting help

Try with an LG remote first...
Check side panel buttons.
Any state change in LED when buttons pressed?

[troxel]

Re: LG 50py2dr Troubleshooting help

I don't have the remote for it, but will check the other buttons when I get home this evening.

[troxel]

Re: LG 50py2dr Troubleshooting help

I am hopefully going to get the remote and some time to look at this again. If main board doesn't respond to the buttons or remote, what is might next step?

Also, is there something missing in the red box? Can't find another photo of the set. Seems odd that there are screw holes, but didn't see any connectors that would go to another board.

Thanks again!

[tom66]

Re: LG 50py2dr Troubleshooting help

Some models have a different fan there, instead of one fan over each sustain board.