LG 42LG5000, vomit colors, bad AS15-F?

[Behemot]

Hello,

I got this TV with colors at picture. Did some research here and found that mostly the synonyme is bad AS15-F chip. It is preset on the T-con, I guess it is the problem?

Tried to push on the ribbons as well to see if they are not badly soldered but no change.

[tom66]

Re: LG 42LG5000, vomit colors, bad A15-F?

I would consider it. If you post a picture of the T-con you can verify the IC is bad with a multimeter.

[Behemot]

Re: LG 42LG5000, vomit colors, bad AS15-F?

Here it comes

[tom66]

Re: LG 42LG5000, vomit colors, bad AS15-F?

OK, these points marked VGMA1 thru VGMA22?

Measure each on DC 20V. TV powered on showing image, board fully installed. Your ground is the metal back plate of the TV.

Report your readings.

[Behemot]

Re: LG 42LG5000, vomit colors, bad AS15-F?

15,45
15,45
15,36
14,53
12,76
10,66
10,80
10,85
8,05
7,42
7,32
2,08
1,92
2,56
5,08
5,27
5,48
7,00
8,46
11,77
13,05
13,64

Also noticed, if I push the chip, color changes.

[tom66]

Re: LG 42LG5000, vomit colors, bad AS15-F?

Are those in order, from 1-22 or 22-1? If so, the chip is definitely bad.

[Behemot]

Re: LG 42LG5000, vomit colors, bad AS15-F?

Yep, 1-22.

OK I'll order some. Been thinking, there are also high quality caps there (Sam Young, Samhwa and such). So far so good, but still, do you think I should change them after replacing the chip?

[tom66]

Re: LG 42LG5000, vomit colors, bad AS15-F?

Uh, I would not consider Samwha high quality. Seen far, far too many fail.
I consider Samyoung average, though, and I haven't seen any fail yet.

[Behemot]

Re: LG 42LG5000, vomit colors, bad AS15-F?

Sarcasm

They are both PoS, but still in 100% condition here (pretty good after all those years). Big ones so they are kept cool, and overall there's not much things heating it inside. But I think I'll change them…more money for me and I'll be assured it won't come back to me in two months with bad caps.

[Behemot]

Re: LG 42LG5000, vomit colors, bad AS15-F?

Oh I think I got it. Output should be 4,92 V max so if it's fried it has supply voltage on output making the display showing overburn colors that's how I can tell it is bad?

[tom66]

Re: LG 42LG5000, vomit colors, bad AS15-F?

Oh I think I got it. Output should be 4,92 V max so if it's fried it has supply voltage on output making the display showing overburn colors that's how I can tell it is bad?

No. The output can go up to 15V. However, it should go gradually from 15V to 0V. As you can see it starts high, goes low and goes high again. This will cause light and dark colours to both appear bright.

The gamma IC is used to make the light output look linear. The TFT in the panel does not have a linear response.