LG 37LC2D No picture, believe bad power supply

[retiredcaps]

Originally Posted by 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?

You could use your DMM.

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.

I just use 60/40 rosin core solder found in my usual sort by lowest price on ebay.

I heard Kester makes very good solder, but so far I have found the cheap 60/40 generic stuff works.

[retiredcaps]

1) Can we get a close up shot of all the connectors so we can see the legend?

2) Can we also get another 2000x2000 shot of the power supply? The existing one is too small resolution.

3) Please use manage attachments this time. With the new server, some people are saying pics load really quick now.

[b700029]

Originally Posted by retiredcaps

1) Can we get a close up shot of all the connectors so we can see the legend?

2) Can we also get another 2000x2000 shot of the power supply? The existing one is too small resolution.

3) Please use manage attachments this time. With the new server, some people are saying pics load really quick now.

Yes I will post this info tomorrow. I will use manage attachments as the server upgrades have seemed to help loading time.

[tmcw]

Originally Posted by b700029

...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

I have a similar 32", and the PS board looks similar to yours, I had a no sound (and other glitchyness), but replacing 10 of the 12 caps you replaced seems to have fixed the TV (thread here: http://www.badcaps.net/forum/showthread.php?t=21321).

Anyway, I was wondering where the green LED should be on the mainboard, I only see 4 red LEDs. I see another LED which is not illuminated.

Also, were your 4 caps near the inverter connection all 105dC caps? Mine were rated 130dC.

Anyway, in addition to the 10 caps I replaced, there were a number of other points I reflowed and added solder to, particularly on the transformer, and a few other spots that looked like they needed it, more like the components with heavier connections like diodes and power transistors.

[tmcw]

Originally Posted by DakotaKid

...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...

@ DakotaKid - do you have a schematic for this powerboard? I couldn't find one.

[DakotaKid]

No I don't. Fortunately, my LG only needed the high frequency caps replaced and it started working like new so I never had to delve into it beyond that.

[retiredcaps]

Originally Posted by b700029

Also, looking at the voltages, what about the 6V that is reading -2.2mv? Is that normal?

I usually don't remember what I had for lunch yesterday so asking me to remember back hundreds of posts ago for a specific voltage is not going to be reliable.

So way back in post #1 (Dec 28, 2011), DakatoKid reported 6V on the 6V rail. So it looks like this is obviously not normal.

So if your soldering is good, then I would start checking around that area.

[b700029]

Hi all, sorry I haven't had a chance to post. Power went out here for about a week (bad storms) and then I got really busy. Retiredcaps, I ordered the replacement 5 caps and am awaiting delivery from DigiKey. I will install those as soon as I get them and let you know how it goes.

Thanks again for your help!

[jh20]

Originally Posted by b700029

Retiredcaps, I ordered the replacement 5 caps and am awaiting delivery from DigiKey. I will install those as soon as I get them and let you know how it goes.

Thanks again for your help!

hi b700029, have you received your remaining caps yet? i'm in the same situation as you. ordered the same caps kit from lcd alternatives and didn't fix the problem

retirecaps, do we need to use low esr caps for those 5 caps in the primary side? low esr caps are very difficult to find in my local (australia) electronics shops.....

[jh20]

updates....

replaced the other 5 smaller caps and problem remains

according to my son (the owner of the tv), it did not become bad slowly over time but rather an overnight thing. sounds like this one is not a bad caps problem after all.....

some readings when the tv is turned on with the remote:

6v is 6.1v
12v is 11.9v
5v is 5.1v
19v is 18.9v

3.4v is fluctuating between 1.1-1.5v !!!

when p202 connector (to av board) is disconnected, 3.4v went up to 1.7v steady. still way below......

i'm at the stage of giving up repairing the psu and would just like to buy a replacement psu, but only if that is most likely going to fix the problem.

would appreciate any advices, based on the findings so far. tia.

edit: the 3.4v-on rail is 2.1v when on. 24v is 23.95v.

[tom66]

3.4V is your problem. Three other users on this forum have had problems with it, including me. On mine, it somewhat worked (picture, but no sound, no DVB, no HDMI, no RC or side-buttons) with 3.4V measuring around 2V. 3.4V-ON is good, but that's only a control signal.

[jh20]

thanks tom66. here's the detail outputs from the psu: (those on the right in brackets are b700029's)

p201:

pin 1 - 3.4v-on = 2.10v (3.37v)
pin 2 - gnd = 0v
pin 3 - 6v = 5.98v
pin 4 - dim = 3.22v (5.15v)
pin 5 - gnd = 0v
pin 6 - st/5v = 5.06v
pin 7 - bri = 2.96v (0v)
pin 8 - err = 3.23v (5.16v)
pin 9 - i-c = 4.56v (0v)
pin 10 - gnd = 0v
pin 11 - st/5v = 5.06v
pin 12 - on = 2.89v (4.39v)
pin 13 - acd = 3.9v (5.15v)

p202:

pin 1 - gnd = 0v
pin 2 - 12v = 11.73v
pin 3 - gnd = 0v
pin 4 - 3.4v = fluctuates betw 1.1 to 1.5v
pin 5 - gnd = 0v
pin 6 - 6v = 5.98v
pin 7 - gnd = 0v
pin 8 - gnd = 0v
pin 9 - 19v = 18.83v
pin 10 - 19v = 18.83v

p203:

pin 1 - gnd = 0v
pin 2 - gnd = 0v
pin 3 - 12v = 11.73v
pin 4 - 12v = 11.73v
pin 5 - gnd = 0v
pin 6 - gnd = 0v
pin 7 - 6v = 5.98v
pin 8 - 6v = 5.98v
pin 9 - gnd = 0v
pin 10 - gnd = 0v
pin 11 - 3.4v = betw 1.1 - 1.5v
pin 12 - 3.4v = betw 1.1 - 1.5v

p204 and p205:

pin 1 to pin 5 - 24v = 23.95v
etc....

some of the voltages from the main board (p201) seems a bit off when compared to b700029's, like the 3.4v-on signal. i've only got 2.1v but his 3.37v?

basically i'm thinking about replacing the whole psu at this stage but really need to be assured it's going to fix the problem and not ended up something else? ta.

edit: btw b700029, your problem is probably not the 12v but the 6v.

[jh20]

bought a new psu and the problem is fixed.

btw in my above post, the pin-outs for p201-p203 are in reversed order. eg, pin 1 of p201 should be pin 13 and pin 13 should be pin 1 etc...

[mericle163]

I found these caps to replace on my TV Power Supply

EEU-FM1E102
EEU-FM1A681
EEU-FM1A471BJ
EEU-FM1A332
EEU-FM1C102
EEU-FM1V102

Is there anyway someone can confirm these are the right ones. Or make a suggestion of better ones.

This forum is very helpful! ! ! ! ! !

[tom66]

Are those Panasonic FM? Those are very good caps. As long as they are the same capacitance, and the voltage is the same or higher, they are fine - check the dimensions too and see that they fit.

[Village Idiot]

I picked up a 37lc2d from the side of the road and was dissapointed when it didn't work.

i replaced all the caps and it still didn't work.

Further investigation revealed the 3.4 v rail was around 1.8V.

Examining the board reveals this voltage rail is generated with an ir3037 SOIC synchronous buck regulator from the 6V rail (I think):

http://www.irf.com/product-info/data...ta/iru3037.pdf

The circuit is similar to the data sheet but with 2.2 Ohm resistors in the chip output to the FETs as well as some diodes. These components are surface mounted on the back side of the board.

I soldered some short wires from the FET gates to hook CRO leads to and remounted the PSU. On the CRO the drive waveform for the 2 FETs looked OK then I realised the TV was now working.

I'm thinking that the problem was a cracked solder joint on one of these components.

[tom66]

Heh, you pick up a curbside TV and you expect it to work? People aren't -that- wasteful.

In my case, I just replaced the PSU, but in future, I would try and replace the IC and MOSFETs. I haven't debugged the circuit enough to know which fails.

It may be a die bonding problem ... you flexed one of the chips, the bonds make contact again. Watch it carefully. It will probably go wrong again.

[Barr]

Hello I had the same issue as the OP and all I replaced was the cap that was bulging and it solved the problem. Thanks for having this on the net, it was a big help.

Barr

[selldoor]

Originally Posted by Barr

Hello I had the same issue as the OP and all I replaced was the cap that was bulging and it solved the problem. Thanks for having this on the net, it was a big help.

Barr

Well Done! If you read further you will know we usually advise replacing
all caps of a similar make and series. If one has gone others will soon follow.
As caps deteriorate they put undue pressure on other components and if they break it may be costlier and more difficult to repair.
It is also important to use caps of the same esr and ripple rating or better or else the repair is unlikely to last as long as the oroginal caps did.

[jamesharris]

Would someone be able to post the cap values at the board locations? I need to double check I've put mine back in the correct spots. I'm missing the 6 volt rail and want to eliminate a wrong cap b4 I proceed any further. I have a service manual for this model but it must be a different chassis. The caps are not the same for the board locations.