Samsung LE37B650 white screen

[aczelkri]

Hey guys,

I have a Samsung LE37B650 screen with the following symptoms:

- Image suddenly turned into almost completely white while I was watching a movie. I can make out some details, but they are very faint. There is definitely an image there, but very very bright and maybe inverted colors.


- If I unplug the cable between the main panel (that has all the video in-out ports) and the tcon board (T315HW02 V3 CTRL BD 31T06 C03), the screen is black as normal (there is backlight and it is masked by the pixels), but of course there is no actual image

- I ordered a replacement t-con board from AliExpress, but it doesn't seem to fix it, the image stays the same.

- If I disassemble the tv panel even further, there are two long panels at the bottom of the led panel. 37T04-S0R VC XR and 37T04-S0U VC XL.



Unplugging the former (XR), half the screen becomes completely white, the other half remains the same "almost white":

Unplugging the latter (XL), half the screen becomes completely white, while the other half improves a little bit, although still very bright:

There is a potentiometer on the XR where I marked, but I didn't dare touch that.

I tried to make measurements on the tcon touching one pin of the multimeter to one of the measurement points on the tcon, the other pin to the tv body:

AVDD: 16V
VGH: 31,2V
VGL: -6V
VCOMF2: 14,73V (I couldn't find any "VCOM" measurement point, so this might not be the right one)

VG1: 15,6
VG2: 15,5
VG4: 13,11
VG6: 11,22
VG8: 10,45
VG10: 7,94
VG11: 7,83
VG12: 7,12
VG13: 7,02
VG15: 5,19
VG17: 4,1
VG19: 2,49
VG21: 0,4
VG22: 0,313

(Interestingly, if I measure the voltages directly on the pins of the gamma chip, the same voltages come off different pins, with some 0s and 16Vs in between.)


Can anyone help me further diagnose the issue?

Thanks
K

[budm]

Re: Samsung LE37B650 white screen

There are no VG3, 5, 7, 9, 14, 16, 18, and 20?
Some of the readings do not look good, I.E. 1 & 2, 12 & 13, 21 & 22 are almost the same.

You should attach good clear pictures of the T-CON board and the whole back side of the TV showing all the boards for us to look at.

What is the history of the TV?

[aczelkri]

Re: Samsung LE37B650 white screen

Hey guys,

Thanks for helping, here you go:






Yes, those are the only dedicated measurement points on the tcon. I did a reading also directly on the legs of the gamma chip. I might have missed or made a mistake with some of them, because the pins are so damn small, but here you go roughly:

VG1: 15,55
VG2: 13,1
VG3: 11,24
VG4: 10,45
VG5: 7,9
VG6: 7,84
VG7: 0
VG8: 16,04
VG9: 15,98
VG10: 7,05
VG11: 5,7
VG12: 4,12
VG13: 2,493
VG14: 0
VG15: 16,04
VG16: 0
VG17: 0
VG18: 0,368
VG19: 0,007
VG20: 0,308
VG21: 0,007
VG22: 16,04
VG23: 0,321
VG24: 0,3

As said the same measurements come off different pins if I read the chip pins directly.


Interestingly, the new TCON board has something called "L271 1555" in the place of the AS15F chip, but otherwise it looks identical to the old one.

I have the 32" version of this TV too and that has a tcon with a different name (T370HW02 VE CTRL BD 37T04 C0J), but that one looks also identical with the only difference that it doesn't even have any chip there. Not any of the tcon variants give a decent picture in the 37" TV.

(Both tcons (old and new) from the 37" TV gives a half-good picture in the 32" TV set: the picture is clearly visible, just somewhat bright.)

So it is either not the tcon or the new ton coming from China is also bad.

Otherwise I bought the TV set around 10 years ago, refurbished, and I never had any problems with it so far.

[nomoresonys]

Re: Samsung LE37B650 white screen

Better make sure that tcon is a match to your panel.

[aczelkri]

Re: Samsung LE37B650 white screen

The tcon I received from AliExpress should be a match as the model number matches completely.

[budm]

Re: Samsung LE37B650 white screen

You need to match the PCBA (Printed Circuit Board Assembly) P/N as printed on the barcode sticker, not the PCB (Blank PCB P/N) since the same model TV may use more than one LCD panel suppliers or version of the panel.

[aczelkri]

Re: Samsung LE37B650 white screen

I think I do have a match, although I am not 100% sure which IDs need to match. Here are two tcon panels:

Old one:




Replacement:

[budm]

Re: Samsung LE37B650 white screen

Barcode sticker P/N 55.37T04.C33 as printed on the barcode sticker.

Blank PCB P/N T315HW02 version 3
You got the right PCB assembly.
So the question is, is the replacement board good or bad?

https://www.shopjimmy.com/samsung-55...n37b650t1fxza/

[nomoresonys]

Re: Samsung LE37B650 white screen

Maybe also test those little ceramic capacitors on your "two long boards". You can test them for shorts or low ohms, multimeter set to 200 ohms test probe on each side of cap, see if any read short or read very low ohms, I would be suspicious of any testing lower than about 100 ohms, most will probably read higher, often only one is bad but it will make several read bad, one technique is to remove one bad one at a time and check it again off the board and recheck any on the board that were reading bad, when you get the bad one off the others will read ok, if that is the problem.

[aczelkri]

Re: Samsung LE37B650 white screen

I tried to check the ceramic capacitors on the long boards (panel PCBs). I didn't find any shorts. Just as well, as I don't have the equipment and skill to remove them off the panel, not to mention put back in.

I measured the voltage at all the available measurement points on the two TCON boards. The old and replacement t-con board produced exactly the same results at each point. (There are some points which I forgot to measure, marked with ?, but I would be quite surprised if they should show any deviation)

point / Old TCON / New TCON
I2VIN1 / 12,4 / 12,4
SDA_I / 3,3 / ?
SCL_I / 3,3 / ?
V3D3 / 3,3 / 3,3
VID2 / 1,2 / 1,2
VGL / -5,92 / -6
VGH / 31,12 / 31,13
VGHC / 29,41 / 29,4
YVIC / 2,78 / 2,77
XOUT_S / 1,69 / ?
XIN_S / 1,62 / ?
HAVDD / 7 / 7
AVDD / 16 / 16
XOUT_M / 1,623 / ?
XIN_M / 1,6 / ?
YDIOU / 0 / 0,011
YDIOD / 0 / 0,178
YCLK / 0,3 / 0,315
YOE / 1,98 / ?
XPOL / 1,6 / 0,65
XSTB / 0,495 / 0,49
BANK_SEL / 0 / 0
SCL / 0 / 0
SDA_GA1 / 0 / 0
VGMA_REF / 15,7 / 15,67
GND_M / 0 / ?
VG1 / 15,66 / 15,6
VG2 / 15,55 / 15,51
VG4 / 13,14 / 13,1
VG6 / 11,27 / 11,24
VG8 / 10,46 / 10,44
VG10 / 7,96 / 7,95
VG11 / 7,84 / 7,83
VG12 / 7,14 / 7,11
VG13 / 7,04 / 7,02
VG15 / 5,21 / 5,18
VG17 / 4,15 / 4,13
VG19 / 2,5 / 2,48
VG21 / 0,4 / 0,394
VG22 / 0,324 / 0,308
edid / ? / 2
REF_F1 / 15,65 / 15,59
REF_F2 / 15,58 / 15,51
REF_F4 / 13,12 / 13,06
REF_F6 / 11,25 / 11,2
REF_F8 / 10,47 / 10,37
REF_F10 / 7,91 / 7,89
REF_F11 / 7,83 / 7,82
REF_F12 / 7,12 / 7,1
REF_F13 / 7,07 / 7,05
REF_F15 / 5,2 / 5,18
REF_F17 / 4,13 / 4,11
REF_F19 / 2,5 / 2,494
REF_F21 / 0,37 / 0,355
REF_F22 / 0,316 / 0,317
VCOM_F / ? / 14,7
VZ_REF / 2,49 / 2,495
PA2_A / 0 / 0

This tells me that either both TCONs are good or both are bad exactly the same way.

VCOM_F seems high, as I read in this forum (tom66's gamma check excel) that it should be between 5 - 10V. Other than that, I don't find anything strange.

What else could I look for?

[aczelkri]

Re: Samsung LE37B650 white screen

Hey guys,

Just thought I would share the details of the successful repair. I took the TV today to a local service facility. The guy told me that the issue with the TV is a very rare one. Still, maybe it helps someone.

What did NOT fix the issue

• Replace the AS15 chip on the tcon board
• Swapping the full tcon board (or any other board) with another one
• Replacing cables

So now, let's skip to the chase: what DID FIX it. Both of the aforementioned "long boards" had an operational amplifier on them each (looks just another IC to me, see images). One of them turned out to be bad. The guy simply unsoldered it from the board and the TV immediately started to work perfectly.

I was shocked to see how removing something and not putting it back can solve things, but the guy said that actually there's quite a few things he could remove from the TV set and it would still operate perfectly.

He removed the chip on a hunch btw, so there were no measurements that could have indicated that it was bad. He just tried and bingo!




Hope this helps someone.

[budm]

Re: Samsung LE37B650 white screen

Very interesting, so did you put all original boards back in place and the TV still working OK?

[dick_barton]

Re: Samsung LE37B650 white screen

Interesting. Appears to be a Gamma correction IC fitted on the narrow panel pcb strip

[budm]

Re: Samsung LE37B650 white screen

I cannot see how Gamma Voltage reference IC (AS34-G) can be removed and still getting correct color gamut.

[aczelkri]

Re: Samsung LE37B650 white screen

We went with the replacement tcon in the end, because the guy ruined the original one in his attempts to replace the AS15 chip on it. So, while I cannot state 100% that the original tcon was not bad, I am pretty sure it wasn't.

There was two of these AS34-G chips, one on each side. He removed just one, and told me that the other one will take over.

I cannot understand it either. I asked whether there will now be double stress on the single chip, he said no, as it only handles digital signals and not big currents.

If anyone knows the answer, please share it here for everyone's benefit

[designspm]

Re: Samsung LE37B650 white screen

Perfect thread, have fixed my 37 Samsung as well.
Firstly have seen on youtube a guy saying the problem is on tcon, bought one but the problem remains the same..
Only after find this thread and changed one of the as34-g the problem has gone.
Thank you!

[ReeceyBurger123]

Re: Samsung LE37B650 white screen

Brilliant information thanks

[xname]

Re: Samsung LE37B650 white screen

Another case of white screen here, succesful case of repair by removing AS34-G. The question was which of them is bad, I desoldered first one and unfortunately it was good, therefore second disassembly and soldering first and desoldering second chip (with front view on the left) led to success. Thanks for THE ADVISE!!!

[Jovica123]

Re: Samsung LE37B650 white screen

Thank you,fixed my samsung 37" by removing this ic (as34-g)

[Davi.p]

Re: Samsung LE37B650 white screen

.