TCL 55S451 Blank screen

[lotas]

And how do you determine that it shows Om, kOm, MOm?

[x_orange90_x]

And how do you determine that it shows Om, kOm, MOm?

I looked at the owners manual online and it doesn't help. That's all I know is it says ex. 5.00 M ohm

I thought that if they read anything other than OL they would be suspect and one bad can make others read bad when they're not. I have another older meter I try and see if it's different.

[nomoresonys]

Capital M for megaohms, small m for milliohms.

[x_orange90_x]

Capital M for megaohms, small m for milliohms.

Thanks for the clarification. I used my other meter and it displayed the capital M as well, but I did notice the readings started out in K ohm and climbed up into the M range. Is it okay then that they are reading that way or should I suspect an issue with one or more?

I still need to get a picture of the lines I blocked off on the ribbon. I didn't get a chance to do it last night.

[x_orange90_x]

lotas

I'm going to reattempt the tape trick tonight and I'll take a photo of it for you. I'm hoping I can find a bad component on the scaler to fix the issue rather than the tape. If I can FIX it the image will be perfect, but the tape trick will likely cause some lines or something.

[x_orange90_x]

If none of the capacitors have low resistance (in Om), then they are fine, show where you masked the contacts.

Attached is a photo of the lines I blocked off. The 4th line is STV, then CKV 8, 7, 6, 5, 4, 3, 2, 1 in that order from left to right. I checked continuity on them to find that's what they are via the test points over each of their resistors. With the tape in place I rechecked and the first untaped one (STV) still has continuity, so I know I blocked off ONLY the clock lines.

I also checked all of the caps for short to ground and all are ok.

[lotas]

Check also VGH, VGL, 3.3v..., there are many more control points there

[x_orange90_x]

Check also VGH, VGL, 3.3v..., there are many more control points there

Ok. Do I just check voltage between the test point and ground with it plugged in and turned on?

[lotas]

Yes, check it out.

[x_orange90_x]

Yes, check it out.

All ribbons attached, no tape, and power on:


DVDDI = 1.83V
HVAA = -3.8mV
VAA = -0.376V
VCM1 = -0.363V
SPI_DI = 120.6mV
SCK = 120.3mV
SPI_CS = 3.25V
SPI_DO = 3.27V
VGL1 = -3.0V and increases toward 0
VGL2 = -8.93V
AVCM = -.362V

[x_orange90_x]

Yes, check it out.

I noticed my labels are quite different from what would be expected. The only one that sticks out to me is DVDDI. Should be 3.5V and I'm under 2V. What do you think?

[x_orange90_x]

I checked the left side voltages with the right side ribbon disconnected and get the following:

DVDD1 = 1.83V HVAA= 6.73V
VAA= 15.32V
VCM1= 4.19V
VSS1= -5.03V
VSS2= -8.91V
AVCM= 4.19V


Notice the left has VSS instead of VGL. So clearly I'm missing voltages on the right. If I check the left side with the right ribbon connected I get almost the exact same readings as the right side, so the right side brings down the left when it's connected.

[nomoresonys]

maybe check all the resistors on the right side.

[x_orange90_x]

maybe check all the resistors on the right side.

I previously did a resistance check on all of them and they read correctly. Should I check them another way? I don't understand how blocking the clock signals gives me grey on the right and image on the left, but uncovering just one makes the whole screen black again.

[x_orange90_x]

Did I lose you guys?

[EazyBone]

Throw it in the trash

[x_orange90_x]

Throw it in the trash

After watching the following video I think I might dust this TCL off and give this a try!

https://youtu.be/bdw8Mub9ReU?si=a2J11CRKriWQSTZP

If I do this, would I apply 12v to the VCC leg of that IC in order to get a "smoking gun"? About how many amps would be appropriate?

Lastly, do you think this may work on my case? 😁

[x_orange90_x]

Update:

I revisited the tape method and successfully found the clock signals, blocked them, and the end result looks great! I can't see any anything wrong with the picture!

[EazyBone]

Well at least you got a 4th garage TV 😂 😂

[x_orange90_x]

Well at least you got a 4th garage TV 😂 😂

😆 I have way more than 4 in there! I fix and resell most of them. Just picked up another 55" Samsung 4k last night.. Added to the "needs backlights" pile along with a 55" Element, 50" Toshiba, and 75" Vizio. Funny thing is, I don't even USE a 4k in the house, only 1080p lol can't really tell the difference

It was just nice to save this one finally because I was probably one more garbage day away from evicting it.