LG 47LC7DF-UK Sound but no Video

[Mongor62]

Just like the title says i have sound but not video

What i have done so far (besides invading someone's thread) is replace the 2 large caps(450v 150uf) and the fuse(250v 5A) near it that was blown and i still have the same problem and the TV works exactly the same as it did before i did anything and with or without that fuse installed, which is now blown just like the original.

I own a Fluke 87 and am a novice at using it. just would like to know where to attack from here but my lack of experience is holding me back.

Power supply model = P/N : 2300KEG021A-F
Main board model = LA75A EAX38059704 (0) 071129 H.Y.H.

Pics are of my TV and i include the plug because my TV is a UK version not a UB version and just trying to find out if it is the wrong region or i have the wrong cord. The version matters because i cannot find any sort of Service manual besides the UB version which is different from mine. The UB version of my TV have separate inverter board and the way i understand it mine has that integrated into the power supply. Also included picture of the cover to the power supply to show the plastic that was distorted due to heat.

Much of this has been posted in another person thread and i am sorry about doing that.

Any help is greatly appreciated.

[Glitcher]

Re: LG 47LC7DF-UK Sound but no Video

You say you have no picture, but does the screen have a glow? Ie. Is the backlight on but the screen is black? If that's the case you may have either a tcon problem or a bad panel.

If there is no glow or backlight, try the flashlight test. Shine a bright flashlight while playing a movie and see if you can see a faint image on the screen. If this is the case you probably have a problem with the psu/inverter circuit.

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

When last i had it on to the best of my recollection it had nothing at all.

As stated in original post it performs the same with and without the fuse and i don't have another fuse (replacement blew) to use but could this test be done without the fuse either way?

[budm]

Re: LG 47LC7DF-UK Sound but no Video

" i did anything and with or without that fuse installed, which is now blown just like the original." So the fuse is still blowing?
OK, just read the post 3 just second before I post. So you do have badly shorted circuit that blow 5A fuse. We will need real good closed up pictures of this power supply-inverter board combo to see what circuit this fuse is feeding. Good top and bottom side of the board, then small section of both top and bottom side so I can clearly see the traces and component to be able to trace out the circuits.
Just remember that we do not have the board in front of us to look, just the pictures.

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

What i mean is the things i replaced were the 2 caps and the fuse which was not working and after i put it back together with the new fuse it blew again. I took the fuse out and still does the exact same thing no video but sound. I do not have another fuse to use atm and before i made another order from digi i was looking for some more advice because ordering 10 fuses wouldn't help me right now, at least i don't think

[budm]

Re: LG 47LC7DF-UK Sound but no Video

We will need the pictures to find out the function of that fuse. I would not keep putting in the new fuse since you can cause more damages until we find out why the fuse blew.

[budm]

Re: LG 47LC7DF-UK Sound but no Video

http://assets.shopjimmy.com/media/ca...36781302_1.jpg
OK, I see the fuse now, that is probably the fuse for the inverter circuits, so more likely that the inverter circuit has shorted out power MOSFETs (they are mounted on the longest heat sink close to inverter transfromers)

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

I already have some pics of the board and you even linked me differences the UB and UK versions of that same power supply so i don't think you are asking for that so i took some more pics of the fuse itself.

As i am a novice i did the best i could to research what fuse to buy to replace this i bought the one linked below.

http://www.digikey.com/product-searc...&formaction=on

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

As i was putting together my last post with pictures you are talking about the very thing i was reading about but i have a lack of comprehension but know the pieces you speak of that are screwed in to the aluminum heat sinks.

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

I numbered the items you speak of to help me understand what you are talking about so if you could take a look and tell me a little more

[budm]

Re: LG 47LC7DF-UK Sound but no Video

6~10 are the components you need to check for very low resistance reading. I cannot tell much more until I can see the bottom side of the board to see how many MOSFETs and how many Diodes for those 6~10 components.
Get the numbers as printed on those components also.

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

These are pics of the bottom of the board and i will take some time to make sure i get the numbers written on those items and get back to you

[budm]

Re: LG 47LC7DF-UK Sound but no Video

Ok, the pictures are kind of blurry. Can you tell me which one of the components form 6~10 has 3 legs?
OK, 5 and 10 are the MOSFETS that we need to test for low resistance reading.
if you at it facing you:
Left pin is 1
Middle pin is 2
Right pin is 3

Use the Ohm meter to test:
Pin 1 & 2
Pin 1 & 3
Pin 2 & 3
Test both ways (swap the probes around after)

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

6. 2pins 920 SFAF508G
7. 2pins K16 R860PF2
8. 2pins K16 R860PF2
9. 2pins 920 SFAF508G
10. 3pins SD20N60 GAY908

pins = legs

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

If i am correct the TV needs to be plugged in and everything connected to do this test?

[budm]

Re: LG 47LC7DF-UK Sound but no Video

No! we are taking resistance reading, not voltage reading. When you report the readings please make sure to tell us if the reading is xxx Ohms, xxx K Ohms, xxx M Ohms.

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

1. 4pins D15XB 60 B018D ("8" has a dash over it and "D" has a dash below it)
2. 2pins MURF1060 SSG A09182
3. 3pins SD20N60 GBY908
4. 3pins SD20N60 GBY908
5. 3pins cannot find any numbers or letters on this item?
6. 2pins 920 SFAF508G
7. 2pins K16 R860PF2
8. 2pins K16 R860PF2
9. 2pins 920 SFAF508G
10. 3pins SD20N60 GAY908
11. 3pins 04N60C3 GAB 918
12. 3pins N 9B FCH10A20 K7A
13. 3pins N 9B FCH10A20 K7A
14. 3pins N 8K FCU20UC30 339
15. 3pins F1 K15 FQPF 27P06

I will be testing the 3pin ones first.

3. meter was showing a M so i figure that means M
Pin 1 & 2 1.256 but climbed slowly from 1.0
Pin 1 & 3 23.68 steady
Pin 2 & 3 335.1 steady

5.
Pin 1 & 2 1.856 steady M
Pin 1 & 3 10.07 steady K
Pin 2 & 3 no reading just says O.L

10.
Pin 1 & 2 13.5 steady NOT K OR M
Pin 1 & 3 13.3 steady NOT K OR M
Pin 2 & 3 .04 steady NOT K OR M

11.
Pin 1 & 2 .425 -.606 and kept rising slowly (this took place over 40 second span) M
Pin 1 & 3 10.09 steady K
Pin 2 & 3 .829 kept rising like 1 &2 M changed to 1.225 slow and i mean slow rising M again changing .9876 M going down

I will do 12 - 15 in a little bit and post this now to keep you from waiting.

[Glitcher]

Re: LG 47LC7DF-UK Sound but no Video

# 10 looks like the culprit looks like all three pins have been shorted on it, replacing it should fix the problem. You should also test 6-9 for shorts also just in case.

[budm]

Re: LG 47LC7DF-UK Sound but no Video

I would replace #5 and #10 at the same time, including the PWM IC (8-pin device next to #5 that drive these two MOSFETS, the resistors/Diode network on the Gate hsould also be checked for damaged.
Take the MOSFETs out and test them out off the board.

[Mongor62]

Re: LG 47LC7DF-UK Sound but no Video

I just wanted to update my readings that i got today just to make sure we are all on the same page.

3. 3pins SD20N60 GBY908
Pin 1 & 2 1.249 M
Pin 1 & 3 23.67K
Pin 2 & 3 1.288M

4. 3pins SD20N60 GBY908
Pin 1 & 2 1.247M
Pin 1 & 3 23.67K
Pin 2 & 3 1.287M

5. I still cannot find a P/N
Pin 1 & 2 2.055M
Pin 1 & 3 10.07K
Pin 2 & 3 OL

6-9 are tested with black lead on 1 and red lead on 2; then next reading is with red lead on 1 and black lead on 2.

6. 2pins 920 SFAF508G
BL1 RL2 1.992M
RL1 BL2 OL

7. 2pins K16 R860PF2
BL1 RL2 .3 OHM
RL1 BL2 .3OHM

8. 2pins K16 R860PF2
BL1 RL2 1.570M
RL1 BL2 1.933M

9. 2pins 920 SFAF508G
BL1 RL2 1.863M
RL1 BL2 1.583M

10. 3pins SD20N60 GAY908
Pin 1 & 2 13.2 OHM
Pin 1 & 3 13.2 OHM
Pin 2 & 3 .3 OHM


11. 3pins 04N60C3 GAB 918
Pin 1 & 2 10.09K
Pin 1 & 3 10.09K
Pin 2 & 3 .3 OHM

I know that its a different section of the board but i got 12 too just in case but 13 and 14 the readings change if i had the negative lead on pin 1 or 2 like the polarity mattered.

12. 3pins N 9B FCH10A20 K7A
Pin 1 & 2 194.1 OHM
Pin 1 & 3 .3 OHM
Pin 2 & 3 193.7 OHM

What does this mean "the resistors/Diode network on the Gate hsould also be checked for damaged."?

I posted a pic of the 8 pin item just checking to see if it the same as what you are talking about. Also i think i have a grasp on ordering CAPS but ordering other things like the MOSFETs (i don't even know if i am using that right) & PWM IC or even Fuses i am very shaky at so a little help here would go a long way.

Having some trouble understanding your schematic.