LG 37LC2D No picture, believe bad power supply

[budm]

I would repalce all the caps on the cold side of the power supply as a set, the hot side (line voltage) capacitors are exposed to only 120Hz, the cold side (DC output side), the capacitors are exposed to 50~100KHz frequency, that is why they have to be low ESR type. I use Panasonic FM/FC series.
http://s807.photobucket.com/albums/y...G/LG%2037LC2D/

[sskillett]

Hey guys. I'm a noob and stumbled onto this thread when searching for a fix for my LG 32LC2D. It has the exact same issue as mentioned above. For the last month or two it would take about 35-45 minutes for the TV to turn on. Last week we started leaving it on continuous and my 5 year old son decided to turn it off. It won't turn back on now (waited over 4-6 hours one day over the weekend). Now I can just see a backlight and nothing else.

I have a decent understanding of electronics and can solder just fine. I have spent 25+ years in the 12V mobile electronics field and work for a office machine repair company full time. I don't normally do board level repairs anymore, but I used to fix alot of Cellular phones back about 15 years ago - especially the old Motorla flip phones and such. I have brought many back from the dead (water damage) over the years. My current job is working on office equipment that costs many times more than this TV. I feel competent that I can do the repair.

That said, I found a site that offers a 'kit' with all of the caps that I need for this TV in one spot. My concern is that they are low quality caps, similar to the ones on my power supply board now. They do state that they use only Panasonic, Nichicon, & Rubycon in their kits.

Is there a better place that I could buy these caps from. I'd love to find them locally, but do not know where any suppliers are for these items in/around the Pittsburgh, Pa area.

If I'm correct in that only the 12 caps total need replaced (8 ea right lower and 4ea middle right in attached board pic). The values I have recorded below...

2ea 3300uF 10V
4ea 1000uF 25V
1ea 1000uF 16V
2ea 1000uF 35V
1ea 680uF 10V
2ea 470uF 10V

Should I be concerned with the remaining caps on the board? None of the caps on this power supply appear to be bulged in any way. I see no splits at the seams either.

Should I plug it back in and check some voltage values? If I knew where to check for what it'd be great.

This is the second time this TV has failed in this way. Last time it was 3 or 4 months out of warranty and LG wouldn't even give me a break on parts. I took it back to the shop I bought it from and they repaired it at a cost of ~$250 (IIRC the power supply was replaced). It has been a little over a year since. Once the TV powers up, it works great. My kid mainly watches cartoons and disney channel on it.

Any help would be appreciated.

[retiredcaps]

Originally Posted by sskillett

For the last month or two it would take about 35-45 minutes for the TV to turn on.

This sounds like symptoms of dry caps or caps that have high ESR (ohms). As the TV warms up, the ESR drops and the TV turns on. Caps with high ESR do not have to bloat.

My standard answer regarding replacing caps (regulars may skip).

http://www.badcaps.net/forum/showpos...84&postcount=3

[DakotaKid]

I don't disagree with what retiredcaps has stated about replacing all of the caps but mine is working perfectly with just replacing the 12 on the high frequency side that you listed. I have had very good experience with Panasonic FM caps.

[The_ferret78]

Thank you for the info on the 37LC2D. Checked the voltage on the same 3.4v rail which was low so I have replaced all the caps and tv is now working great again and even has its picture quality back. Cost for parts was $5.20 and an hour to repair

[tom66]

Awesome. I have the same TV with a low 3.4V rail (measures 1.2V!) but strangely it still has a picture. Did your TV lose sound then remote control features before completely dying? Or did it just take a long time to turn on one day?

[The_ferret78]

Mine just stopped one day then would work for an hour or two then it just went black but no sound or picture when it happened

[sskillett]

Mine has been working great since I replaced the caps. Just like new.

I thought I had already posted this, but I don't see it. Thanks to all for their replies.

[b700029]

Hi guys,

I have a 37LC2D with the same problems as most mentioned here, not turning on. Actually it would attempt to turn on with a blinking light about 14 or 15 time and then shut-off. Nothing is displayed on the screen, the backlight doesn't kick on either.

So IO took a look at the power supply and found the 16v 1000uf caps were bulging, only 2 of them. I decided to replace all 12 caps with higher quality ones and now when I try to turn the TV on it the front panel blinks 3-4 times and then has a solid Green LED. I also am not seeing the green LED on the main board that is normally there when the everything works.

My friend has the same exact TV, same board and everything and he was nice enough to let me swap his board into my TV to see if it was something more than the power supply. I turned the TV on and it worked right away.

These are the caps and quantities i replaced

2 - 3300 105°C
2 - 1000 105°C
4 - 1000 105°C
1 - 1000 105°C
1- 680 105°C
1- 470 105°C

So, my question is what else could be bad on my board? I do have a DMM but it does not measure capacitance.

Thanks in advance

[retiredcaps]

Originally Posted by b700029

I decided to replace all 12 caps with higher quality ones and now when I try to turn the TV on it the front panel blinks 3-4 times and then has a solid Green LED.

These are the caps and quantities i replaced

2 - 3300 105°C
2 - 1000 105°C
4 - 1000 105°C
1 - 1000 105°C
1- 680 105°C
1- 470 105°C

1) What brand and series did you use for replacements?

2) It doesn't look like you replaced ALL the electrolytic capacitors. I don't see any smaller value caps like the startup capacitor which is generally 47uF 50V.

3) A picture of your board would also help.

[DakotaKid]

Originally Posted by b700029

Hi guys,
My friend has the same exact TV, same board and everything and he was nice enough to let me swap his board into my TV to see if it was something more than the power supply. I turned the TV on and it worked right away.

It sounds like either your 12V and/or 24V outputs aren't right. I would re-solder all of the caps you put in and make sure nothing is shorted, grounded, or open that shouldn't be and of course, check the brand and series as retiredcaps has suggested. Check the 12V and 24V outputs for good stable voltage. I don't have the schematic in front of me but usually the 12V is needed to deliver video thru the T-con and 24V is needed for the backlight inverter. You might do the flashlight test and see if you have video but no backlight (then 24V is your problem) or, if you do have backlight but no video, it sounds like your 12V is the problem. The 5V or low voltage rail seems to be working or I think you'd be getting red LED instead of green.

[b700029]

Hi guys, sorry for the delayed response. Thank you for your replies.

Retiredcaps, thanks for your response. See my answers below:

1. I am not sure of the brand or series. On the caps there are the following markings. 1N12TX, 1N30TK, 1N14TX along with their uF rating and voltages.

2. I didn't replace all the caps, only the 12 that came in a kit that I purchased from LCD Alternatives. These are supposedly the most common to go bad. Only 2 of them were bulging but I replaced the 12 supplied in the kit.

3. See a few pictures of the board. Sorry for not attaching those earlier.

DakotaKid, I was thinking of resoldering them all over again. Is there a way to check to see if they are making contact with the board? I do have a DMM but no capacitance test available. How would I go about checking the 12V and 24V voltages? I did plug the TV in and tried turning the power on completely in the dark and there is nothing on the screen before originally posting. I am familiar with what a backlight issue would be like as I have dealt with it on a few laptops before. There is definitely no power to the screen at all. Before, I replaced the caps I was getting the Red flashing LED. Now it is a green flashing LED then solid green.










Hopefully the pictures are clear enough. Let me know your guys' thoughts.

Thanks in advance

[retiredcaps]

Originally Posted by b700029

1. I am not sure of the brand or series. On the caps there are the following markings. 1N12TX, 1N30TK, 1N14TX along with their uF rating and voltages.

They look like Panasonic FM/FR caps.

2. I didn't replace all the caps, only the 12 that came in a kit that I purchased from LCD Alternatives. These are supposedly the most common to go bad. Only 2 of them were bulging but I replaced the 12 supplied in the kit.

Rant time again. Some of the sellers on ebay or that have their own website selling cap kits CHEAP OUT and don't provide all the caps.

The startup cap is typically 47uF 50V and is CRITICAL to the proper operation of a SMPS power supply.

3. See a few pictures of the board. Sorry for not attaching those earlier.

Arrgh, serves me right for not asking you to attach them versus posting inline. I figured you have been here long enough to know my pet peeves.

How would I go about checking the 12V and 24V voltages?

1) Put your multimeter on DC volts.

2) Put your black probe on a power board ground screw and leave it there. This is your ground.

3) Put your red probe on each pin on each connector. Report you reading like so

Connector CN100
pin 1 legend says 12V - I got 11.99
pin 2 legend says BLON - I got 3.00
etc

[b700029]

Wow thanks for the quick reply retiredcaps.

How would I know which one is the startup cap?

These are the other electrolytic caps that were not replaced. (Does not include the ones wrapped in black coating)

450V 150uF (Largest one on the board)
450V 68uF
50V 100uF
50V 10uF
50V 33uF
50V 4.7uF (definitely says 4.7 and not 47 on cap)
35V 47uF

Also, just want to double check. I should have the power hooked up while checking the pins in each connector, right? Should I try to turn the TV on or leave it in the off state?

I will check the voltages tomorrow, thanks again for all your help!

[retiredcaps]

Originally Posted by b700029

How would I know which one is the startup cap?

It might be one of the two that I circled in red.

These are the other electrolytic caps that were not replaced. (Does not include the ones wrapped in black coating)

450V 150uF (Largest one on the board)
450V 68uF
50V 100uF
50V 10uF
50V 33uF
50V 4.7uF (definitely says 4.7 and not 47 on cap)
35V 47uF

So the last 5 may have cost the seller an extra $1 in caps (in volume) to buy and to exclude them in mind baffling to me.

That is why DIY ordering is almost always better than "kits".

Also, just want to double check. I should have the power hooked up while checking the pins in each connector, right? Should I try to turn the TV on or leave it in the off state?

Yes, plug it in, power it on. Try getting readings in the on state.

[b700029]

Originally Posted by retiredcaps

It might be one of the two that I circled in red.



So the last 5 may have cost the seller an extra $1 in caps (in volume) to buy and to exclude them in mind baffling to me.

That is why DIY ordering is almost always better than "kits".



Yes, plug it in, power it on. Try getting readings in the on state.

Thanks for the tips, unfortunately I didn't realize the 5 other caps would be excluded from the kit. Would Radioshack be the best place to pick up the other 5 caps if they are determined to be bad?

P201 Connector

Pin 1- 3.4V -- 3.37V
Pin 2- GND -- (-1.8mv)
Pin 3- 6V -- (-2.0mv)
Pin 4- DIM -- 5.15V
Pin 5- GND -- (-1.5mv)
Pin 6- ST/5V -- 5.16v
Pin 7- BRI -- Varies from 131-186mv
Pin 8- ERR -- 5.16V
Pin 9- I-C -- 11.7mv
Pin 10- GND -- (-.1 mv)
Pin 11- ST/5V -- 5.16V
Pin 12- ON -- 4.39V
Pin 13- ACD 5.15V

P202 Connector

Pin 1- GND -- (-2.5mv)
Pin 2- 12v -- 11.2v
Pin 3- GND -- (-2.2mv)
Pin 4- 3.4V -- 3.49V
Pin 5- GND -- (-2.2mv)
Pin 6- 6V -- (-2.2mv) (I double checked this value)
Pin 7- GND -- (-2.2mv)
Pin 8- GND -- (-2.2mv)
Pin 9- 19V -- 18.69V
Pin 10- 19V -- 18.69V

P203 Connector

Pin 1- GND -- (-2.8mv)
Pin 2- GND -- (-2.8mv)
Pin 3- 12V -- 11.21V
Pin 4- 12V -- 11.21V
Pin 5- GND -- (-2.3mv)
Pin 6- GND -- (-2.3mv)
Pin 7- 6V --(-2.2mv) Double checked
Pin 8- 6V -- (-2.2mv) Double checked
Pin 9- GND -- (-2.2mv)
Pin 10- GND -- (-2.2mv)
Pin 11- 3.4V -- 3.49V
Pin 12- 3.4V-- 3.49V

P204 Connector

Pin 1- 24V -- 25V
Pin 2- 24V -- 25V
Pin 3- 24V -- 25V
Pin 4- 24V -- 25V
Pin 5- 24V -- 25V
Pin 6- GND -- (-3.0mv)
Pin 7- GND --(-3.0mv)
Pin 8- GND-- (-3.0mv)
Pin 9- GND -- (-3.0mv)
Pin 10-GND -- (-3.0mv)
Pin 11- BRI -- 130-187mv varies
Pin 12- IC-- 11.7mv
Pin 13- DIM 5.16V
Pin 14- ERR 5.0mv

P205 Connector

Pin 1- 24V -- 25V
Pin 2- 24V -- 25V
Pin 3- 24V -- 25V
Pin 4- 24V -- 25V
Pin 5- 24V -- 25V
Pin 6- GND -- (-2.8mv)
Pin 7- GND --(-2.8mv)
Pin 8- GND-- (-2.8mv)
Pin 9- GND -- (-2.8mv)
Pin 10-GND -- (-2.8mv)
Pin 11- BRI -- 130-187mv varies
Pin 12- IC-- 11.7mv

P206 Connector

Pin 1 - ERR 5.15V
Pin 2 - GND (-2.8mv)

Hope that gives you enough info. Thanks in advance again!

[retiredcaps]

Originally Posted by b700029

Would Radioshack be the best place to pick up the other 5 caps if they are determined to be bad?

1) Get them from digikey.com. Their first class mail shipping option is only $2.75 ish and you will likely get the caps in 72 hours or less. Get Panasonic FM or FC brand and series.

P202 Connector
Pin 2- 12v -- 11.2v
Pin 9- 19V -- 18.69V
Pin 10- 19V -- 18.69V

P203 Connector
Pin 3- 12V -- 11.21V
Pin 4- 12V -- 11.21V

2) As DakotaKid mentioned in post #31, it looks like your 12V rail is low. At 11.21V (6.5% off), I suspect that is not enough for the components to work. If the reading were 11.85V, then I wouldn't be suspicious.

3) I would start by checking your soldering work by giving the caps a gentle, but firm tug to make sure they are in place properly.

4) I recommend replacing the remaining caps with these (assuming diameter fits - and double check my selections)

http://www.digikey.com/product-detai...2392-ND/613753

http://www.digikey.com/product-detai...0316-ND/266325

http://www.digikey.com/product-detai...0320-ND/266329

http://www.digikey.com/product-detai...0315-ND/266324

http://www.digikey.com/product-detai...1232-ND/356135

5) I was correct about the pricing too (in post #35). In quantities of 100, each cap above is less than 20 cent each.

[b700029]

Thanks RC. Sorry it took me so long to respond. The boards were down for maintenance as you probably know.

Regarding the 12V, how would I know which caps this relates to? Or would this be one of the five caps that was not replaced?

Also, looking at the voltages, what about the 6V that is reading -2.2mv? Is that normal? It doesn't seem to be. I am thinking I may resolder the connections on each cap and try taking voltages again.

Should there be no movement in the capacitor? Some of them are easier than others to move.

I'll check your links and let you know if they all fit.

Thank you again!

[retiredcaps]

Originally Posted by b700029

Regarding the 12V, how would I know which caps this relates to? Or would this be one of the five caps that was not replaced?

I would check all your soldering first.

Also, looking at the voltages, what about the 6V that is reading -2.2mv? Is that normal? It doesn't seem to be. I am thinking I may resolder the connections on each cap and try taking voltages again.

Hmm, I didn't see those voltages. Good thing we all got a break. 6V isn't a "common" voltage that we see on TVs or lcds.

Should there be no movement in the capacitor? Some of them are easier than others to move.

They should all be firm and flush to the board. If you can move them, they may be cold solder joints.

[b700029]

I am going to recheck all my solder points first and see if any of them need to be resoldered. Can I check to see if they are making a contact by using a DMM and checking continuity? Also, do you recommend any specific solder for EL caps? I am out of solder and need to pick some up anyway, I figured I would check with you as you seem extremely knowledgeable.