Lg 37LG6000 lcd tv

[budm]

Re: Lg 37LG6000 lcd tv

"But as it's cooled, it now reads 10.69uF and ESR = 5.9." at room temp? That is bad.

[newtothis]

Re: Lg 37LG6000 lcd tv

Sorry about that, but as you probably realise, I'm just learning all this and there's a lot to take in. I'm not sure that I'd recognise a cold solder joint yet, unless it was blatantly obvious, anyway.

So... I've now tested all the caps on the top board. The 25v and 35v caps seem OK.

C111 is a Sam Young 105C NHA 450v 10uF cap. I tested it after desoldering and it was reading 11.01uF and ESR = 1.6.

But as it's cooled, it now reads 10.69uF and ESR = 5.9.

There aren't any values for ESR in the NHA datasheet.

Wow really bad, Worst cap i have had is 1.2

[selldoor]

Re: Lg 37LG6000 lcd tv

Wow really bad, Worst cap i have had is 1.2

Was that on a BIG cap are these testers accurate for that size a cap?

See here
https://www.badcaps.net/forum/showthread.php?t=8990

I will try and look at some myself later but 5.9 may not be too bad if good caps can be 5.00

Perhaps needs its own discussion thread

[oddbodd]

Re: Lg 37LG6000 lcd tv

Yes it's at room temp [~20C]. Just tested again , now showing ESR = 5.2 and 5.3.

I guess a replacement won't do any harm...

[budm]

Re: Lg 37LG6000 lcd tv

I always replace the cap as a set, not just the one that shown bad (the 450V one I rearely replace) so I will not have to do them again for years from now.

[selldoor]

Re: Lg 37LG6000 lcd tv

I always replace the cap as a set, not just the one that shown bad (the 450V one I rearely replace) so I will not have to do them again for years from now.

Hi budm just to be sure - this is a 450v cap he is testing.

[budm]

Re: Lg 37LG6000 lcd tv

Ah, i thought it was the 19uf low voltage cap on post 9, sorry, did not read all the posts from the beginning again since it is getting long and lost track.

[oddbodd]

Re: Lg 37LG6000 lcd tv

Well, I remove, tested and replaced most of the caps on the bottom board, and found nothing untoward. The only ones I didn't test were the big KMF 450v 82uF caps [tomorrow].

However, the power on light now stays on, after turning from red to white four times. It then dims a little. I'll replace the 450v cap on the top board with the high ESR, and see it that makes any difference.

Still no picture or sound, though. The remote will turn the set off [red standby light] but takes 10 seconds. It also responds to power on [straight away], but nothing else.

I've now had the set powered on for about 45mins, to see if anything happens after it's warmed up sufficiently... but no change.

[selldoor]

Re: Lg 37LG6000 lcd tv

You should still try the hairdryer not too hot -do each board in turn and see if any make a difference.
Also have you done any voltage tests at the connectors yet?
Do them first with everything connected - if you probes cant connect use a sewing needle in each pin hole and test against the needle.

[oddbodd]

Re: Lg 37LG6000 lcd tv

I did try with the hairdryer, but it made no difference - except with the possibility that the power on light may have come on a bit quicker when I heated that 450v cap.

Testing connectors will be next.

[oddbodd]

Re: Lg 37LG6000 lcd tv

After leaving the set in a cold room [~10C or lower] over the weekend, I plugged it in this afternoon.

The power on light only cycled red/white twice, and then everything started to light up. It only lasted for as few seconds, though. After that, it was back to four red/white cycles.

I replaced that 450v cap, but it made no difference.

Test results of the connectors...

Top board...

P101
pin1 400v = 376-382v
pin2 N/C
pin3 N/C
pin4 GND
pin5 VCC = 12.9-13.2v
pin6 SGND

P201
pin1 16v = 15.9v
pin2 GND
pin3 12v = 12v
pin4 GND
pin5 5.2v = 5.1v
pin6 5.2v = 5.1v
pin7 GND
pin8 GND
pin9 ERR
pin10 PWR = 2.9v
pin11 A-DIM
pin12 SEL

P203
pin1 24v = 24v
pin2 24v = 24v
pin3 24v = 24v
pin4 24v = 24v
pin5 24v = 24v
pin6 GND
pin7 GND
pin8 GND
pin9 GND
pin10 GND
pin11 BRI
pin12 I-C = 3.0v
pin13 DIM
pin14 ERR

P206
pin1 24v = 24v
pin2 ACD = 5.1V
pin3 PVT = 2.9v
pin4 12v = 12.3v
pin5 GND
pin6 GND
pin7 GND
pin8 GND
pin9 GND
pin10 5.2v = 5.1v
pin11 5.2v = 5.1v
pin12 5.2v = 5.1v

Bottom board...
P206 connects to P206 above - same readings
P601 connects to P101 above - same readings

[oddbodd]

Re: Lg 37LG6000 lcd tv

After leaving the set in a very cold room overnight again, I brought it in and turned it on. Lo and behold, it powered up fine. It's the first time I've actually seen it work. I tuned in all the free digital channels, and left it powered on for about an hour. I powered off and tried to power on again immediately, but it wouldn't, reverting to the red/white cycling of the power on light.

It seems like it starts better from very cold. Any ideas why that would be?

[vinceroger69]

Re: Lg 37LG6000 lcd tv

you could get a can of freeze spray and try to locate the faulty item that way some tins of air duster will work as freeze spray if held upside down.

[oddbodd]

Re: Lg 37LG6000 lcd tv

One step forward, two steps back...

Today, I decided to test the set in the cold room.

I guessed that it'd start up OK, just as it did yesterday, so I warmed part of the top board that has a few caps, and powered on. It started up OK. Then warmed the other half of the top board, and it restarted OK again. It would seem that the top board is OK.

Moved to the bottom board, and warmed some caps on the secondary side, plugged in, and nothing! Not even the power on light!

Tested some voltages on the connections, and on the primary side found only 160v on P601 pin1 [400v], where I'd been getting ~380v previously.

[selldoor]

Re: Lg 37LG6000 lcd tv

Check meter is on VDC - sorry I have gone missing- decorating sons new house.

[selldoor]

Re: Lg 37LG6000 lcd tv

I think there is a post in here somewhere where someone suggested checking the diodes and ceramic caps. I also recall a board that acted similar to yours and it was a ceramic cap
that was either shorting when it got hot or it was cracked and went open when it got hot.
So having narrowed it down to a board perhaps something to try and look for.
Laborious job !!

[oddbodd]

Re: Lg 37LG6000 lcd tv

No problem. Yes, voltmeter was on VDC. I have scrutinised everything with a magnifying glass, but can't see any cracks. I'll have another look, though.

Can the diodes and ceramic caps be tested in place?

[selldoor]

Re: Lg 37LG6000 lcd tv

Yes its not always conclusive as they are often in series/parallel with others distorting the results - not actually done a whole board myself - once tried a few capacitors where they had a colour change from others on the board. Perhaps PM the earlier poster and ask
for advice on how best to test as he may not see this post.


Momaka said this in another thread

"And ceramic caps as well. Any ceramic cap that measures less than 30 ohms is suspect and the circuit it's in should be checked to see if that measurement makes sense."

[oddbodd]

Re: Lg 37LG6000 lcd tv

OK, thanks. I'll test those.

Just when I thought I was getting somewhere... I'm nearly ready to give up on this one.

[oddbodd]

Re: Lg 37LG6000 lcd tv

I've tested all the ceramic caps on the bottom board, and theyre all within 10%.

6 x SD471K caps all measure between 444pF and 465pF.
2 x R471K caps measure 479pF and 480pF.
2 x R221K caps measure 218pF and 223pF

I've started testing diodes in circuit, removing a couple as well.

ZD503 [1N5 223 B] was testing zero both ways in circuit, but on removal seemed OK. On replacing, it tested zero both ways again. Three identical ones on the board test OK in circuit. Also see pic.

Does that sound right?

A quick power on test, and I'm now only getting 25v on the 400v connector pin1 at P601.