LG 37lc55

[ronhayes]

Hi All
I have a LG 37lc55 in for repair was told if left unplugged for a few days it would come on and work fine for a few hours then shut down going into stby
When I switched on it came on and stayed on displaying a very good picture and stayed on for a few hours. so the next day I powered up the set again and it stayed on I checked all the suspect caps on the power supply board and all looked fine so I used hair dryer on power supply board as mentioned in previous post on this set and sure enough the set went into stby and when pressing power button on set or remote it would start up then shut down again.
So I changed all the caps on power supply board as mentioned in the previous post I changed nine caps in total and then reinstalled the power supply board and then powered the set up again, The set powered up fine nice picture good sound but after about 2-3 mins it went to stby and could not get it to power up again it would power up then goes straight to stby again.
Has any one had this problem with this set , If so do they know what other component's fail in this set?
Any help would be much appreciated.
Ron

[Andrew F. Ali]

Re: LG 37lc55

Hi..I trust the replacement caps you installed were hi-grade. Look for loose connections, cold solder joints and cracks on the power and main board also.

[ronhayes]

Re: LG 37lc55

Hi All
Could really do with some more help with this set. I have changed all the caps in the power supply for hi-grade caps, But the set still goes to st/by this is happening after about ten mins. I have checked for loose connections but can not find any and also checked p/s board and main board for and dry or cracked joints all looks ok.
Any pointers or has any one had this happen with one of these sets before any help would be much appreciated.
Ron

[Alastair E]

Re: LG 37lc55

Does PS-ON go to 0 when this happens?

Need to determine whether the mainboard is turning off the PSU or the PSU just quitting....

[budm]

Re: LG 37lc55

I would try this, force on the PS_ON pin (the PS_ON wire must be disconnected from the main board) and see if the TV will still go into STBY mode.

[Dgtech]

Re: LG 37lc55

I'm a little late here but I just finished one of these sets just the other day. Here are the caps that I replaced:

2200 uF 10V
C202
C217
C221
C206
C208
C218

470uF 25V
C222

470uF 35V
C226

Just making sure nothing was missed.

[ronhayes]

Re: LG 37lc55

Hi All
Thank you for your help. Firstly to Dgtech yes I have changed all those caps with hi-grade caps. Secondly to Alastair E and to budm Their are two multi connection plugs coming from the main board to the p/s board but their is no reference to ps_on pin their is two pins marked st5v on off.
Are these pins marked up on the main board? As I have not yet removed the main board and cannot see markings on the connections as this board is covered with metal sheeting.
And when you say disconnect this pin do you mean pull the complete ? or just release the one wire from the multi-connection plug connected to the main board?
Thanking you all for your help.
Regards Ron

[ronhayes]

Re: LG 37lc55

Hi All
I have now pulled the main board on this set so I could gain access to the multi plugs to see if I could locate PS-ON pin , But still could not locate PS-ON pin could see a power on pin so assumed this was what was mentioned. I disconnected this pin and results were , when the set was plugged in the set would be in st/by press power on the remote and set would try to power up back lights would power up momentarily then flicker on /off and then stay off, sound would come on so you know set is on then after a couple of seconds the set would go to st/by again if you repeat the pressing of the power button the same thing would happen again and again. So I then reconnected this wire to power on pin and it made no difference it still did the same back light on momentarily then flicker on/off then stay off sound but no picture then back to st/by.
Does this give anybody any clues as to what is happening to this set.
Any more help would be much appreciated.
Regards Ron

[ronhayes]

Re: LG 37lc55

Hi All
I have added a couple of pictures of the main board hoping someone can tell me which is the ps-on pin ?
Regards Ron
[/ATTACH][/ATTACH][/ATTACH]

[Dgtech]

Re: LG 37lc55

I'm guessing right now in saying that PS_on may be the same as the Power on - indicated on the larger connector?

[Dgtech]

Re: LG 37lc55

Its kinda weird the way they did the designations on the side of the connector with it not going pin for pin along side, however, there are 13 pins and 13 designations. I'd just count off and check all of the voltages and post them all...just to be sure.

[ronhayes]

Re: LG 37lc55

Hi All
Still having problems with this set ? When switching on today the set came on and stayed on for over half an hour with out any issues and allowed me to carry out some voltage measurement's to the large multi plug going to the main board measurements taken from plug on main board (and assuming the dot on board as being pin one blue wire connected) I took measurements whilst set was on and then put set into st/by and then carried out measurement again.
Then after this I brought set out of st/by pressing power on remote blue light came on on t-con board (momentarily) sound came up back lights flickered on/off set went to st/by pressed power again and the same happened again sound back lights flickering on/off then st/by this happened a couple more times then on about the fifth time set came on and stayed on.
Does this give anybody any clues as to what is happening ?
Here are the measurements that I found on the large multi plug with the (power on pin).
All measurements taken in the 20v range on multi meter.
st/by set on
1= 4.60 1= 4.60
2= 0.04 2= 2.50
3= 4.61 3= 4.48
4= 0.00 4= 0.00
5= 0.00 5= 1.37
6= 0.00 6= 4.64
7= 0.00 7= 3.06
8= 4.61 8= 4.48
9= 0.00 9= 0.04
10=0.00 10=3.04
11=0.16 11=5.92
12=0.00 12=0.00
13=0.04 13=3.18
Regards Ron

[ronhayes]

Re: LG 37lc55

Any feed back would help with this set?
Regards Ron

[ronhayes]

Re: LG 37lc55

Hi All
Can any one give me any pointers on this set ?
Does anyone know if their is any other problems with the power supply board after all the caps have been changed ? It has a ic701 24c256 e-prom 0n the main board does any one know if this is likely to be the culprit for this problem, same as the Samsung has ic1803
which is also a e-prom 24c256 and caused problems with the power supply in 42 inch models ?
Any help much appreciated Ron

[dcapper]

Re: LG 37lc55

Do you know how many hours are on the set? I found the main capacitor went on a Panasonic 42" plasma. It had 19,000 hours. I was beating myself up trying to locate the trouble. Most people overlook it.

[ronhayes]

Re: LG 37lc55

Hi dcapper
Do you mean the 450v cap? as to how many hours are on the set I do not know I will have to find out how to get into service mode and check this out ? not sure how many you are supposed to get on a lcd ?

Regards Ron

[ronhayes]

Re: LG 37lc55

Hi All
Firstly a big thank you to (downunder) for his help with this fault.
As downunder quoted I checked sm caps on main board C533 and C901 both 16v 100uf although they both seemed fine and checked with cap meter and were reading 101.7 and 103.1 but changed anyway set has stayed on since changing these caps set was on for 3hrs last night, Then when switched on this morning it came straight on and has stayed on all day. I have put in st/by a couple of times just to see that it fires up ok, And all seems fine.
So a big thank you to all that replied and a big thank you to downunder for his help.
Hope this helps others with this post.
Regards Ron

[Alastair E]

Re: LG 37lc55

Have a look at the thread I did on my 32lc56.

Looks to be same/similar mainboard--that has known issues with inductors.

Basically--you short out all the inductors adjacent to the power-plug as they go intrmittent. The link to the SVC is in that thread too...