LG42lg50 UG power on and off

[Stormyme]

Re: LG42lg50 UG power on and off

I am having a hell of a time getting a clear image of this for some reason. But if you zoom in this picture you can see the pin names match the front. The ACD is the 4th pin and retesting showed 0. I can't unhook those two cables on that side to center this power supply for a better picture.

[budm]

Re: LG42lg50 UG power on and off

See that chart for the 4 pins?

[Stormyme]

Re: LG42lg50 UG power on and off

Now I see what your after and the discovery came too late, my camera battery died. lol I was able to grab 2 more shots before it did. If these aren't good after zooming in I have to wait about 30-45 minutes for the battery to charge to try again.

[budm]

Re: LG42lg50 UG power on and off

So now you have ALL the pin names, and now you can test all the Voltages of all the pins (except GND pins) from the top side since you can see what those 4 pins are now.
You must provide the pin names and follow by the Voltage readings, you can skip the GND pins.

[dick_barton]

Re: LG42lg50 UG power on and off

Hello Budm
Following through your logic it does make sense that the power supply must be fully up and running for the screen to produce a display, as you say, even though it's only short lived.


Stormyme
Can you tell me what the voltage is on the ACD Pin (pin 18 post #57) when you switch on and then when the display shuts itself off.

[Stormyme]

Re: LG42lg50 UG power on and off

Hello Budm
Following through your logic it does make sense that the power supply must be fully up and running for the screen to produce a display, as you say, even though it's only short lived.


Stormyme
Can you tell me what the voltage is on the ACD Pin (pin 18 post #57) when you switch on and then when the display shuts itself off.

Yeah that is the one that was bothering me all night. I was wondering why I was getting two different readings on that pin only. When I retested it, I saw what was happening. When the back light flashes on its 4.1 and when standby flashes its 0. So is the power supply at fault or is it another boards fault for not doing what its supposed to? lol

By the way this whole experience has been exciting, fascinating and a complete learning experience. Normally when a tv breaks in this house, my guy just hauls it out to the recycle and we save up to buy a new one. But I have always hated doing that. Maybe because my father was an engineer and fixed everything lol We had a Sony that broke down and out it went last year. Troubleshooting this one this time has me thinking about that Sony. I think it would have been a simple T-con board replacement to fix it. I love learning new things and most of all love learning how to fix things. Thank you all of you. Your my new hero's lol

[dick_barton]

Re: LG42lg50 UG power on and off

Hello Budm, Could do with your thoughts on this one. Is the ACD dropping out causing the problem. Looking at the training manual mentioned above the ACD is an output to the main board and I would have thought that it would be independent of any main board issues

[dick_barton]

Re: LG42lg50 UG power on and off

In the meantime Stormyme, grasp the white connector across its body and pinch it hard. That should release the clip holding it tightly in place so that you can pull it out of the socket.

[vinceroger69]

Re: LG42lg50 UG power on and off

dick barton/budm in the lg training manual page 30 and 31 what about carrying out those two tests will thay prove the psu is ok and its not that at fault?

http://www.manualslib.com/manual/701579/Lg-42lg70.html

[dick_barton]

Re: LG42lg50 UG power on and off

Hello vinceroger69.
I think we may both be thinking along the same path. The reason I have asked Stormyme to remove the connector is to check that the ACD voltage is present at switch on and remains on and not drop out as it appears to be doing while connected to the main board.
Thanks for your input.

[Stormyme]

Re: LG42lg50 UG power on and off

Hello vinceroger69.
I think we may both be thinking along the same path. The reason I have asked Stormyme to remove the connector is to check that the ACD voltage is present at switch on and remains on and not drop out as it appears to be doing while connected to the main board.
Thanks for your input.

Oops I missed this request I now have the connector from the main board unplugged from the power supply. I have the connector from the inverter board disconnected. That was the only way I was able to snapshot it. Did you want that plugged back in? Is the power to be on during the retest of the 18 pin? Probably so, but you never know lol

[dick_barton]

Re: LG42lg50 UG power on and off

Once the P201 connector has been disconnected use the red lead to measure the voltage on the ACD pin while the black lead is on the chassis. Turn the TV on and see how long it takes before the ACD voltage falls to zero. You can check it say once a minute for a couple of minutes. If it falls to 0V then it's a faulty power supply.

[dick_barton]

Re: LG42lg50 UG power on and off

This is taken from the service manual:-

"Standby should be present at connector P201, Pins 9,10,11 or 12. If Missing remove AC Power and unplug Connector P201, apply AC Power and recheck for presence of both 5 Volt Standby and ACDetect. Loss of either 5 Volt Standby or AC Detect would be a Power Supply Failure. Presence of 5 Volt
Standby and AC Detect would be an indication of a failure on the Main Board."

[budm]

Re: LG42lg50 UG power on and off

This is taken from the service manual:-

"Standby should be present at connector P201, Pins 9,10,11 or 12. If Missing remove AC Power and unplug Connector P201, apply AC Power and recheck for presence of both 5 Volt Standby and ACDetect. Loss of either 5 Volt Standby or AC Detect would be a Power Supply Failure. Presence of 5 Volt
Standby and AC Detect would be an indication of a failure on the Main Board."

That is correct, the ACD will tell the main board that the incoming AC Voltage is too low or too high for the TV to operate, the signal (0V = BAD) is sent to the main board and main board will shutdown the PS-ON signal.
So I am confused on her V reading because she had the V for the pin wrong so I do not for sure if the ACD is ALWAYS present on not hence all that details of the pin names in the picture I marked up.
You can pull the ACD wire from the power supply connector and use 1K resistor between 5VSTBY and the ACD pin of the main board to fool the main board that the AC input is OK.

[dick_barton]

Re: LG42lg50 UG power on and off

Hi budm, It took quite a bit of sorting out but because I too was very confused as to whether or not the ADC was constantly present.
I've asked for P201 to be disconnected and the above test carried out. It appears from the details Stormyme supplied that on one reading it was high and when read another time it was low.
I'm hoping this test will remove all doubts.
Thanks for your help.

[budm]

Re: LG42lg50 UG power on and off

Hi budm, It took quite a bit of sorting out but because I too was very confused at whether or not the ADC was constantly present.
I've asked for P201 to be disconnected and the above test carried out. It appears from the details Stormyme supplied that on one reading it was high and when read another time it was low.
I'm hoping this test will remove all doubts.
Thanks for your help.

OK, if she can use the resistor to fool the main board and the problem goes away then the next step will be looking at the ACD detection section on the power supply board, what usually fail in the ACD are the sensing resistors, the Optoisolator.

[vinceroger69]

Re: LG42lg50 UG power on and off

OK, if she can use the resistor to fool the main board and the problem goes away then the next step will be looking at the ACD detection section on the power supply board, what usually fail in the ACD are the sensing resistors, the Optoisolator.

thanks budm im sure theres a few of us learning from this thread too and with your experience it helps us too learn when were stuck too in trying to help her fix her tv .

[dick_barton]

Re: LG42lg50 UG power on and off

It's a pity I can't find the schematic for the power supply. I've seen quite a lot of posts saying the resistors in series tend to be a problem.

[vinceroger69]

Re: LG42lg50 UG power on and off

there is one in one of my posts but its hard to read you can just make it out with a magnifyer glass so not much good.

EDIT LINK http://electro-medical.blogspot.co.u...lgp42-08h.html

[Stormyme]

Re: LG42lg50 UG power on and off

Once the P201 connector has been disconnected use the red lead to measure the voltage on the ACD pin while the black lead is on the chassis. Turn the TV on and see how long it takes before the ACD voltage falls to zero. You can check it say once a minute for a couple of minutes. If it falls to 0V then it's a faulty power supply.

Well this is surprising lol Touching the pin next to the label of ACD with power on reads 5.0. Waiting a minute reads 5.0. Waiting two minutes reads 5.0. Unplugged the tv and same pin reads 0.

To be sure I did the test correctly, The only connector that was not plugged in was the p201. The pin tested was the 18 pin according to your picture on thread 57.

Awaiting your instructions. Running to the market real quick.