LG LCD power supply

[vinceroger69]

Re: LG LCD power supply

just a update for budm i had a bit of spare time today so i checked the psu again i used flux and solder braid on the ic pads that i have removed the short has now gone i persume it was u200 causing the short are these ok as replacements i know there from china but finding replacements cheap in the uk without minimum order costs etc im struggling to find a supplier.
http://www.ebay.co.uk/itm/2820147396...%3AMEBIDX%3AIT IRF7807
http://www.ebay.co.uk/itm/3019086960...%3AMEBIDX%3AIT IRU3037

[budm]

Re: LG LCD power supply

That should be fine.

[vinceroger69]

Re: LG LCD power supply

That should be fine.

ok will order them thanks budm.

[vinceroger69]

Re: LG LCD power supply

Budm im about too fit the new parts too this board but in post 34 you asked me to remove two filter MLC CAPS on the 5VST pins, bud any idea what uf and voltage these need to be? as i cant find the ones i removed as i removed the ones of my spare board too.

Edit ive found the value in the service manual 10 uf 16 v 1206 size

[vinceroger69]

Re: LG LCD power supply

Just a update i have replaced the three ics and the two mlc caps good news the psu now runs without any clicking problems the bad news is the 3.4 volt line is low 1.1 volts so no freeview etc this seems a common fault on these psu s with no reported fixes most people just replace the psu any idea budm what i can do to fault find next also what pins do i link to run this psu on the bench (i know this is a psu issue as i had another 37 inch set with sound issue once i replaced all caps and was fine, and the set im repairing runs fine with the borrowed psu) 37 inch set nowreturned though so cant run anymore tests.

[budm]

Re: LG LCD power supply

The 3.3V is generated by that U200 and the MOSFETs which you have already replaced, so at least the shorts circuit is gone due to the Buck converter circuit (u200, MOSFETs) was bad, but now the shorts is gone and you get the 6V back but the output of the Buck converter is only putting out 1.1V, so there may be more bad parts in that section.
Low output can be due to heavy load, you may try disconnecting the 3.3V line out from the connector to see if it will come back up to 3.3V. It can also be due to bad feedback circuit, or bad caps in the output.

[vinceroger69]

Re: LG LCD power supply

The 3.3V is generated by that U200 and the MOSFETs which you have already replaced, so at least the shorts circuit is gone due to the Buck converter circuit (u200, MOSFETs) was bad, but now the shorts is gone and you get the 6V back but the output of the Buck converter is only putting out 1.1V, so there may be more bad parts in that section.
Low output can be due to heavy load, you may try disconnecting the 3.3V line out from the connector to see if it will come back up to 3.3V. It can also be due to bad feedback circuit, or bad caps in the output.

thanks budm i will run more tests do you know which pins in need to bridge on the psu so i can run it out of the set.

just to note when i used a working psu in this set it worked fine (wanted to rule out cracked screen) so fault must be on this psu somewhere.

[budm]

Re: LG LCD power supply

thanks budm i will run more tests do you know which pins in need to bridge on the psu so i can run it out of the set.

just to note when i used a working psu in this set it worked fine (wanted to rule out cracked screen) so fault must be on this psu somewhere.

I do not have good pictures of the top side of the board to clearly see the labels for each pin of the connectors on the power supply board.
If you run the power supply board by itself, do you get any DCV at the 3.3V (3.4) pins?

[vinceroger69]

Re: LG LCD power supply

budm from post 103 in this thread it looks like the 3 ics i changed dont do the 3.4 volts can you have a quick read of the thread as it maybe the other 3 ics ive not chaged i will get pictures of the connector writing tomorrow for you.
https://www.badcaps.net/forum/showth...t=18218&page=6
and no only 5 volts standy present but will comfirm this tomorrow.

[budm]

Re: LG LCD power supply

https://www.badcaps.net/forum/attach...5&d=1463429645
The U200, Q204, Q205 are the one you changed, right? They are for the 3.3V that converts the 5V STBY down to 3.3V.

[vinceroger69]

Re: LG LCD power supply

https://www.badcaps.net/forum/attach...5&d=1463429645
The U200, Q204, Q205 are the one you changed, right? They are for the 3.3V that converts the 5V STBY down to 3.3V.

yes thats the three ive changed just checked but reading that other post/thread made me think as following the diagram in that thread it looked like the 3.4 volts went too those other ics hence me asking too make sure.

[vinceroger69]

Re: LG LCD power supply

Hi budm this isnt my psu but shows the connectors quite well which two do i need to bridge with a 1k resistor so i can test the psu on the bench thanks

this shop jimmy link maybe better though as you can zoom in better
http://www.shopjimmy.com/lg-67099000...wer-supply.htm

[budm]

Re: LG LCD power supply

I cannot see all the lable of the pin from SJ picture due to the angle of the picture.
I see ON pin (may be for the Inverter ON/OFF) and the 3.4V ON pin.
Check to see what you have on those two pins when you turn the TV on and off since you can at least turn the TV ON but the 3.3V is low.
If those two pin toggle Low (TV OFF) and toggle HIGH (TV ON) then more likely those are the two command receiver pins that you can connect the resistors to for manually forcing on the power supply board.

[vinceroger69]

Re: LG LCD power supply

cheers budm ive also just ordered all the capacitors so will do a full recap too as this will rule them out then, also this low reading on the 3.4 rail seems very common on the internet with no fixs posted but must be something like you say above quote the Buck converter is only putting out 1.1V, so there may be more bad parts in that section.
Low output can be due to heavy load, you may try disconnecting the 3.3V line out from the connector to see if it will come back up to 3.3V. It can also be due to bad feedback circuit, or bad caps in the output quote. Can you highlight the capacitors on the output budm then i can check/change them thanks

i have also disconnected the 3.4 wire from the conncetor still reads 1.1v so it wasnt that maybe you have some ideas what to check next and thanks again budm

[budm]

Re: LG LCD power supply

https://www.badcaps.net/forum/attach...5&d=1463429645

I see c202 for input filter, C210 on the output, then you can trace the '3.3V OUT' trace to see if it has more caps connected to that trace.

[budm]

Re: LG LCD power supply

BTW, are you getting the 12V at the connector?

[vinceroger69]

Re: LG LCD power supply

yes 12 volts fine ok i will do the recap first (should all be here tomorrow) then will retest and go from there so far i have tested all the smd resistors around the ics ive replaced if there a easy check i can do on the smd capacitors in circuit?

[vinceroger69]

Re: LG LCD power supply

update ive fully recapped psu tested all voltages 3.4 v is not there with 3.4 on linked to 5v stb and 5v stb pin linked to on pin all the other voltages are spot on now just tested q204 it has 5volts in but no voltage on the other 4 pins on the opostie side of the chip so where do i start fault finding? thanks guys

[vinceroger69]

Re: LG LCD power supply

some pictures also d200 diode on heatsink has 5 volt on centre leg nothing on outer legs is this correct fch10u10 not sure if this has anything to do with the 3.4 volt section though.

[vinceroger69]

Re: LG LCD power supply

so in this diagram i have 5 volts into the q204 ic i have already changed nothing on the otherside of the ic can anything else be stopping the output? i guess a new ic can be faulty?
im not sure why yesterday i measured 1.1 volts on the 3.4 line maybe somehow the mainboard was giving this readings to the pins now running the psu on the bench no voltage at all on the 3.4 volt pins.