LG42lg50 UG power on and off

[vinceroger69]

Re: LG42lg50 UG power on and off

The right side of that connector results

0
0
0
04.1
04.1
0
5.0
5.0
0
12.2
0
15.6

ive added these to one post too see if its easier to understand maybe budm will have a idea what to check next if the voltages are ok.

[Stormyme]

Re: LG42lg50 UG power on and off

I added the readings to one picture

[dick_barton]

Re: LG42lg50 UG power on and off

Hello,
Can you confirm that all the legends are alongside the correct pin numbers.

Can you put the your meter on the Error Pin and switch on and monitor what happens to it. Is it 0V when set is switched on and then does it go to 4v when it goes into standby

[budm]

Re: LG42lg50 UG power on and off

The right side of that connector results

0 = N.C.
0 = PWM-DIM
0 = ON/OFF
04.1 = ACD
04.1 = GND
0 = GND
5.0 = 5V
5.0 = 5V
0 = GND
12.2 = 12V
0 =GND
15.6 = 16.5

OK, the reading does not make sense since some of the pins are GND pin so there should be no Voltage on it.
You need to put the pin names next to the readings.
The name of the right column as printed on the board:

N.C = NO CONNECTION = XX V
PWM-DIM = PWM Backlights Dimming control = XX V
ON/OFF = backlights ON/OFF control pin = xx V
ACD = AC detect = XX V
GND =
GND =
5V = 5VSTBY =
5V = 5V STBY =
GND =
12V =
GND =
16.5V =

Per your reading on number 5 you show 4.1V which cannot be since it is GND PIN.
If you look at the bottom side of the board, there are pin names which are not printed on the top side of the board.

[Stormyme]

Re: LG42lg50 UG power on and off

OK, the reading does not make sense since some of the pins are GND pin so there should be no Voltage on it.
You need to put the pin names next to the readings.
The name of the right column as printed on the board:

N.C = NO CONNECTION = XX V
PWM-DIM = PWM Backlights Dimming control = XX V
ON/OFF = backlights ON/OFF control pin = xx V
ACD = AC detect = XX V
GND =
GND =
5V = 5VSTBY =
5V = 5V STBY =
GND =
12V =
GND =
16.5V =

Per your reading on number 5 you show 4.1V which cannot be since it is GND PIN.
If you look at the bottom side of the board, there are pin names which are not printed on the top side of the board.

OK I am sorry, on retest the two readings of 04.1 are 0. Apparently I didnt angle the lead enough for the reading.

[budm]

Re: LG42lg50 UG power on and off

So please report the readings with pin names for both Columns, the left column pin names you will have to take the board out to look at the labels as printed on the bottom side of the board.

[vinceroger69]

Re: LG42lg50 UG power on and off

OK I am sorry, on retest the two readings of 04.1 are 0. Apparently I didnt angle the lead enough for the reading.

EDIT budm posted whilst i was typing.

What budm means i think is on the underside of the power board under the connector pins you have been measuring the pin markings should be printed by the connector fixing this is on the under side of the board so you will have to remove it to turn it over, basically unplug the set from the mains remove all the wire connectors going to the main board etc (making a note which connector goes to which plug etc) remove any screws from the power board and lift of the tv chassis, BE CAREFULL THOUGH AS SOME OF THE LARGE CAPACITORS CAN STORE A VOLTAGE EVEN WITH THE SET OFF AND UNPLUGGED.

[budm]

Re: LG42lg50 UG power on and off

Example of what are printed on the bottom side of the board:
http://assets.shopjimmy.com/media/ca...2-bottom_1.jpg
Once you see th names of the pins then you just write down the name matching the pin, put the board back in place and make the measurement from the top side.
So far it does not look like you have problem with the power supply board.

[dick_barton]

Re: LG42lg50 UG power on and off

Hello Budm,
I think it the lack of a suitable AC Detect voltage that is causing the problem. If that is not being sent to the main board from the power supply then it goes into error mode.

Attachment from an LG4270 Training manual

[Stormyme]

Re: LG42lg50 UG power on and off

Example of what are printed on the bottom side of the board:
http://assets.shopjimmy.com/media/ca...2-bottom_1.jpg
Once you see th names of the pins then you just write down the name matching the pin, put the board back in place and make the measurement from the top side.
So far it does not look like you have problem with the power supply board.

Can we go with your assessment of the power supply not being the problem and move onto what your experienced gut is telling you it might be? I am only trying to minimize my chances of being fried. lol

[vinceroger69]

Re: LG42lg50 UG power on and off

If its not the power board it could be the main board as you was already having issues with hdmi etc the trouble is main boards are hard and some time impossible to fault find so we just change them whats the part number of the main board and pictures of any stickers with printing/writing on the main board as they will need to match your replacement (we maybe ableto help you locate one then) thats if the others agree it is the mainboard at fault.

[dick_barton]

Re: LG42lg50 UG power on and off

Hello Stormyme,
I appreciate it takes a while and there's a lot of questions being asked but without the unit in front of us it is difficult to come out with a definitive answer. Remote servicing is difficult at the best of times.

My last post has just placed the problem squarely on the power supply. It is not sending out any voltage on AC_Detect which the main board requires. It tells the Main Board that the incoming mains supply voltage is within safe limits ie not too high or low for the set to operate.

Hopefully Budm and Vinceroger69 can give their opinion too on the lack of AC_Detect

[Stormyme]

Re: LG42lg50 UG power on and off

Hello Stormyme,
I appreciate it takes a while and there's a lot of questions being asked but without the unit in front of us it is difficult to come out with a definitive answer. Remote servicing is difficult at the best of times.

My last post has just placed the problem squarely on the power supply. It is not sending out any voltage on AC_Detect which the main board requires. It tells the Main Board that the incoming mains supply voltage is within safe limits ie not too high or low for the set to operate.

Hopefully Budm and Vinceroger69 can give their opinion too on the lack of AC_Detect

I completely understand the difficulties. Can't blame a girl for trying lol
OK removal of power supply it is I will get those numbers and snapshots of main board while im at it too.

[vinceroger69]

Re: LG42lg50 UG power on and off

Hello Stormyme,
I appreciate it takes a while and there's a lot of questions being asked but without the unit in front of us it is difficult to come out with a definitive answer. Remote servicing is difficult at the best of times.

My last post has just placed the problem squarely on the power supply. It is not sending out any voltage on AC_Detect which the main board requires. It tells the Main Board that the incoming mains supply voltage is within safe limits ie not too high or low for the set to operate.

Hopefully Budm and Vinceroger69 can give their opinion too on the lack of AC_Detect

Im still learning my self and have just downlaoded that training manual too have a read of im sure budm will advise about the ac-dect voltage etc but in the mean time it maybe still worth removing the power board and taking a pictuure of the connector area and any pin markings as it may help budm diagnose the issue.

[dick_barton]

Re: LG42lg50 UG power on and off

Hi vinceroger69
That's my problem too. Last time I was repairing TV's big time, they were CRT' sets with transistors and the odd sprinkling of IC's. Quite different to today's modern sets.

[vinceroger69]

Re: LG42lg50 UG power on and off

Hi vinceroger69
That's my problem too. Last time I was repairing TV's big time, they were CRT' sets with transistors and the odd sprinkling of IC's. Quite different to today's modern sets.

Im 46 now so started electronics as a hobby late in life but getting there with repairs and learning more. just takes time reading and learning schematics etc and buying/building more test equiptment etc.

[dick_barton]

Re: LG42lg50 UG power on and off

Having another look through the LG4270 Training manual, the power supply output connector shown in it looks very similar to that in the LG42LG50UG and if so the pinouts should be as per the attached drawing.

Please Stormyme could you confirm for the last time that the voltages you read on those pins match what's shown in the drawing and also the labels alongside the connector also match what is on the board.

If all the voltages match then I suspect as I said earlier the power supply is at fault and is not providing any AC_Detect voltage (3.5V ->5.0V) to the main board and so the set is going into standby.

[Stormyme]

Re: LG42lg50 UG power on and off

Having another look through the LG4270 Training manual, the power supply output connector shown in it looks very similar to that in the LG42LG50UG and if so the pinouts should be as per the attached drawing.

Please Stormyme could you confirm for the last time that the voltages you read on those pins match what's shown in the drawing and also the labels alongside the connector also match what is on the board.

If all the voltages match then I suspect as I said earlier the power supply is at fault and is not providing any AC_Detect voltage (3.5V ->5.0V) to the main board and so the set is going into standby.

OH post #45 in this thread answers that question I think. Those readings of 04.1 were wrong.
I just got home so I will be pulling that power supply now.

[budm]

Re: LG42lg50 UG power on and off

Hello Budm,
I think it the lack of a suitable AC Detect voltage that is causing the problem. If that is not being sent to the main board from the power supply then it goes into error mode.

Attachment from an LG4270 Training manual

-According to the readings, the ACD has 4.1V.
And for her o be able to see the "NO SIGNAL" on the screen, that means the PFC is working, the inverter is working, the main board is sending the signal to the T-CON to produce 'NO SIGNAL' on the screen so obviously the Voltages and signals are present to be able to see 'NO SIGNAL' on the screen.. If the ACD is bad then there will be no backlights. The ACD is for the protection to shutdown the power supply if the incoming AC is too high or too low.

[Stormyme]

Re: LG42lg50 UG power on and off

One quick question. The tv has been unplugged for over an hour. Is there still current in that power supply? Should I be wearing rubber shoes? lol