TCL 55S451 Blank screen

[EazyBone]

Re: TCL 55S451 Blank screen

I don't see why not. Could short both sides. You really want this TV to work lol. But yes, good multi meter helps, I figured that out early

[x_orange90_x]

I have been thinking about this stupid tv again and really wanting to get it figured out. Everyone I see with similar models either have a bad TCON or a bad main board causing the blank screen. In my case I don't have a TCON to replace, though I've replaced the main twice.

What is the likelihood of THREE main boards being bad and all exhibiting the exact same symptoms?

I really do want to test the scaler boards but I have no idea where to probe. I've watched several videos of it being done but they're mostly in Hindi language and they never show HOW to IDENTIFY your 12v, 3.3v, etc test points on YOUR OWN tv. Obviously mine will be different from theirs. If I were to post full pictures of the scalers would someone be able to help me identify the test points?

Edit:
There is a sticker on one of the scalers with the number PT550GT05-3 on it. Googling that number brings up TCON boards with the same exact number. Maybe that's helpful, maybe it isn't.

[EazyBone]

Just test if any of the capacitors are shorted. Turn multimeter to beep beep and test both sides of each cap on there.

[x_orange90_x]

I just checked every capacitor on the right side and they all tested good. Beep on one side and not on the other. Didn't check the left side yet but something tells me they'll be good too.

[x_orange90_x]

Update! I disconnected the right side ribbon and got an image on the left side! I did this probably a dozen times before and didn't get an image but now I do. I checked all of the resistors on that sides scaler and they all tested good, and so did the caps. I pinned out the CKV lines and blocked them off but I just get a gray image on that side and the left side is fine. Is there something else that needs to be taped off along with the clock lines?

[lotas]

Post a photo in full, in good quality, of the faulty buffer strip and your photo, which contacts you masked.

[x_orange90_x]

Post a photo in full, in good quality, of the faulty buffer strip and your photo, which contacts you masked.

Here's some photos of that side. I need to get another of the outside edge but this is a start. Also, I used my multimeter on continuity and touched one probe to CKV test point and the other to the pins on the ribbon. I determined it's lines 4-12 and blocked those off, that's how I got the grey screen on that side.

I also attached a screenshot of the pinout for that chip.

[lotas]

And you can see this entire bar; this chip is a spi flash.

[x_orange90_x]

And you can see this entire bar; this chip is a spi flash.

I will get a photo of the whole bar later when I get home. Is there something specific you're looking for? I can try to get a close up of it if so.

[lotas]

Yes, I’m interested in the very edge of this bar, what components are located on it.

[x_orange90_x]

Yes, I’m interested in the very edge of this bar, what components are located on it.

Here are the pictures. The one with the black tape is the end you asked about.

[lotas]

Yes, now you can see that there are no protective diode assemblies here; you checked the ceramic capacitors for low resistance with the cable disconnected.

[x_orange90_x]

Yes, now you can see that there are no protective diode assemblies here; you checked the ceramic capacitors for low resistance with the cable disconnected.

I don't think it was unplugged. I can recheck them.

[x_orange90_x]

Attached is a picture of the readings I got, going from the left side of the strip to the right. The caps not listed read OL. I'm guessing probably only one cap is bad but pulling down the others? I notice that all that read low are positioned in the middle of the strip instead of near the top where most of the others are.

[lotas]

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

[x_orange90_x]

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

Are those readings normal then despite the others reading OL?

I will try to get you a picture of what I masked off. It was on the main board side of the ribbon but that should't matter since I pinned the traces for continuity.

[lotas]

Well then, compare with the working strip what resistance they have on the capacitors, you just need to disconnect the cables going to the t-con. You may have masked more contacts than required, and now power is not supplied to the non-working strip, but I don’t see what you masked there, maybe half of the cable is masked there.

[x_orange90_x]

Well then, compare with the working strip what resistance they have on the capacitors, you just need to disconnect the cables going to the t-con. You may have masked more contacts than required, and now power is not supplied to the non-working strip, but I don’t see what you masked there, maybe half of the cable is masked there.

You reminded me just now, I did check them on the working side and they all read OL.

[lotas]

Attached is a picture of the readings I got, going from the left side of the strip to the right. The caps not listed read OL. I'm guessing probably only one cap is bad but pulling down the others? I notice that all that read low are positioned in the middle of the strip instead of near the top where most of the others are.

I can’t understand what resistance is, what is it in megaohms, milliohms...?

[x_orange90_x]

I can't understand what resistance is, what is it in megaohms, milliohms...?

Here is my meter:

https://www.innova.com/products/hand...10-megohm-3306

It's an auto ranging 10 MegOhm meter. It's "M" not "m" on my display, don't know if that helps.