TCL 55S451 Blank screen

[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.

[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 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]

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]

Re: TCL 55S451 Blank screen

@EazyBone

I got a new multimeter that has several more functions than my old one. Just used it to diagnose and fix another tv, so I'm ready to come back to this one. I am trying to understand how there can be a problem with BOTH scaler boards. The only conclusion I can draw is that it may be water damage, but I don't see any evidence of this. Most of these no display issues I read about are the main board or TCON. Since I don't technically have a TCON, and I've tried 3 different main boards, there's only the two ribbons and the scaler boards left.

I watched a video of a guy checking surface Mount caps on a TCON and they appeared shorted when he tested them, but when he removed the right side ribbon those caps were good. He found a shorted cap on the right side scaler board, replaced it, and the tv worked again.

It seems highly unlikely for both to have a problem unless it WAS water damage that isn't evident, or the original main somehow shorted BOTH sides and that's why my replacement mains aren't making any difference.

There are a couple of caps I can see on the scalers, so I'm at least going to check those for now.

[x_orange90_x]

Re: TCL 55S451 Blank screen

Yes you can replace them. The likely hood of you finding shorted caps or something on both sides is extremely low. I have been through several shorted panels and I have never found one cap that was shorted. That doesn't mean it's not possible, but some lines from tcon can go directly to panel. This is such a cheap TV I wouldn't even bother. I would salvage parts, if you do that, and trash it. Obviously try and use your multimeter first, but don't waste too much your time lol

I hadn't seen anything labeled as such, but I'm wondering if there is a fuse on each scaler that may have blown from something. TCONs have a fuse, and because there are ICs on the scaler boards I imagine there should be a fuse to protect them.

I'll have to get my multimeter out and start checking what I can.

[EazyBone]

Re: TCL 55S451 Blank screen

Yes you can replace them. The likely hood of you finding shorted caps or something on both sides is extremely low. I have been through several shorted panels and I have never found one cap that was shorted. That doesn't mean it's not possible, but some lines from tcon can go directly to panel. This is such a cheap TV I wouldn't even bother. I would salvage parts, if you do that, and trash it. Obviously try and use your multimeter first, but don't waste too much your time lol

[x_orange90_x]

Re: TCL 55S451 Blank screen

I tried both ribbons like that and still nothing. I've been watching videos of people testing the voltages on the TCON. Since I don't have one, those components are on the scaler boards of the panel (just learned that!) I'm starting to think something is shorted on both scalers. Is it feasible to replace potentially shorted components on these?

[EazyBone]

Re: TCL 55S451 Blank screen

Since you don't know which side you have to do one side at a time. Generally when I do this test it's always where the purple is. I haven't had a short in the middle of the ribbons yet, so just move the piece of tape around covering roughly 8 pins all in the purple area (just a estimate in drawing). Try pins 1-8 then if no go try pins 3-11 then try 5-13.

Nothing at all may happen, but at some point when you plug it in you would get a picture of there is a short on one side of the screen. Just keep moving the tape, take 10 minutes and do quickly. Hit power if it didn't work, unplug do next. It doesn't always work.

If you ain't getting anywhere with it then just move on to next tests you may want to try. It could be shored on both sides, it could be some screen damage you also don't see. I have got many tvs where the person said their son threw something at it but the glass isn't broken.

[x_orange90_x]

Re: TCL 55S451 Blank screen

Use tape to cover like 8-12 pins. Start all the way on left and move over 3-5pins at s time. This does not mean it's going to work because both sides could of shorted at the same time. This may not work at all, it's not a guarantee but it does help.

Also no, generally you get no results until you hit the shorted spot. Once you do, the screen will turn on both sides, or with Samsungs at least will stop the boot loop.

Could you markup the attached picture of which areas your talking about? I was focusing on the inner sides (right edge of left ribbon, left edge of right ribbon)

Edit:
Okay so I hadn't really looked beneath the connectors until now and I THINK I may have found the clock lines or at least where they're located. I believe I read somewhere else that clock lines connect between the left and right connects. Check the second attached photo and see what you think.

[EazyBone]

Re: TCL 55S451 Blank screen

Use tape to cover like 8-12 pins. Start all the way on left and move over 3-5pins at s time. This does not mean it's going to work because both sides could of shorted at the same time. This may not work at all, it's not a guarantee but it does help.

Also no, generally you get no results until you hit the shorted spot. Once you do, the screen will turn on both sides, or with Samsungs at least will stop the boot loop.

[x_orange90_x]

Re: TCL 55S451 Blank screen

Just pick random spots. I do this with Samsungs and they have no tcon either sometimes. Just make sure unplugged before moving any cables always

When you pick a random spot to place the tape, do you always get some sort of result? When I tried two different spots there was no change at all. When a pixel shorts in the panel it could cause this blank screen issue because it messes up the clock signal on that side. In this case something catastrophic has to be happening to these panels (because this is pretty common from what I've read), because at least one side of the screen should do something but it's not.

[x_orange90_x]

Re: TCL 55S451 Blank screen

I got the correct main board and put it in. Still no image. Exact same problem. Backlights on, sound, but no image. I tried putting a sliver of tape on some random spots on one of the ribbons but no change. With either one or both ribbons disconnected I still have a black backlit screen.

[EazyBone]

Re: TCL 55S451 Blank screen

Ok I'll see what I can do.

Since you're pretty apt with this repair, and Samsungs in particular as you started, could you look over at my other thread about a Samsung and see what you think?

https://www.badcaps.net/forum/showthread.php?t=123151

You could try the exact same tape method there as well. With Samsungs if I just disc the ribbon sometimes I get blank screen as well, but with tape it fixes. ** nothing is actually fixed, but shows a better image then before. I've never fixed a Samsung panel short.

I'm unfamiliar with that issue though, so I really wouldn't be of any help on that tv. I've never actually seen something like that. The other people posting in that thread would know more. If I were to pick something though I would say bad tcon or bad panel.

[x_orange90_x]

Re: TCL 55S451 Blank screen

Just pick random spots. I do this with Samsungs and they have no tcon either sometimes. Just make sure unplugged before moving any cables always

Ok I'll see what I can do.

Since you're pretty apt with this repair, and Samsungs in particular as you started, could you look over at my other thread about a Samsung and see what you think?

https://www.badcaps.net/forum/showthread.php?t=123151

[EazyBone]

Re: TCL 55S451 Blank screen

Just pick random spots. I do this with Samsungs and they have no tcon either sometimes. Just make sure unplugged before moving any cables always

[x_orange90_x]

Re: TCL 55S451 Blank screen

Here's a picture. You can start by covering the same or double the amount of pins like he is doing. He is doing the driver board ribbons. Can use scotch, masking, thinner is better. If you put it in the correct spot and reconnect it (all ribbons connected) the screen will fully turn on, depending on how much tape you use you may see lines in-between full picture or color discoloration but it will show like the actual Roku logo/home screen. It won't just show like vertical lines, if it does just show vertical lines the screen might be suspect then. In the end, if you get an image at all, then maybe it's the correct track. I'd try with the original main board though, since you feel you may of got wrong version.

It may do nothing at all and give exact same results.

I just watched the following video and it was extremely helpful, however I still don't know what to do in my case.

https://m.youtube.com/watch?v=pfrRhw7-ZII

Because the tcon is built into the main board on my model, the labeling of the traces is different. They do not say CK for Clock nor do they terminate quite the same as in the video, which looks very straightforward.

Check out the pics of his instruction vs what my board looks like.

[EazyBone]

Re: TCL 55S451 Blank screen

Here's a picture. You can start by covering the same or double the amount of pins like he is doing. He is doing the driver board ribbons. Can use scotch, masking, thinner is better. If you put it in the correct spot and reconnect it (all ribbons connected) the screen will fully turn on, depending on how much tape you use you may see lines in-between full picture or color discoloration but it will show like the actual Roku logo/home screen. It won't just show like vertical lines, if it does just show vertical lines the screen might be suspect then. In the end, if you get an image at all, then maybe it's the correct track. I'd try with the original main board though, since you feel you may of got wrong version.

It may do nothing at all and give exact same results.

[x_orange90_x]

Re: TCL 55S451 Blank screen

Orange, if you disconnect one at a time, it Should show a picture, but not always. Sometimes I don't get a picture until I put some tape around. You may expect it but sometimes it doesn't happen. But yes it would suck lol. I just try it because it takes 5 minutes to move tape, plug in, repeat few times on each side and then I move on. BUT if you got a wrong board, might as well try that as it's coning

I have nothing to lose trying the tape method. Can you give me since instruction on where to put it? Would it be on the outside edges of the ribbons or the insides? Cover just a few pins? I've seen it done on YouTube but no one ever really explains what they're doing exactly.

Also, what side effects are present after successfully doing this? Is the screen flipped, mirrored, lines, ghosting, etc.?

[EazyBone]

Re: TCL 55S451 Blank screen

Orange, if you disconnect one at a time, it Should show a picture, but not always. Sometimes I don't get a picture until I put some tape around. You may expect it but sometimes it doesn't happen. But yes it would suck lol. I just try it because it takes 5 minutes to move tape, plug in, repeat few times on each side and then I move on. BUT if you got a wrong board, might as well try that as it's coning