Toshiba 55G310U No Picture

[selldoor]

Re: Toshiba 55G310U No Picture

You mean a bad picture of a tcon board - we need to see the whole thing.

Actually no we dont- its the same as budms earlier post but its replacement time- burnt up!!

Never seen that on here before - no external intervention - stray wire or touching anything?
from top or bottom. - Was it in a position where water could have dripped onto it etc.

[bwilliams60]

Re: Toshiba 55G310U No Picture

You don't like my picture?
There was no external intervention from what I can see and no evidence that any liquid had found its way to the board. It just burnt up so there must have been a problem with the chip itself or elsewhere on the board. The fuse did not blow on the TCON board so ......????
Well I am thinking about it, what is the voltage applied to that fuse? Does anybody know? I guess I could go measure it.
Do you guys still need a picture of the TCON board or anything else from this set?

[bwilliams60]

Re: Toshiba 55G310U No Picture

Update. I have replaced the TCON board on this unit which had a bad chip on it as you can see from the picture. Bought new one from ShopJimmy and installed earlier this evening.Same results. I shut all the lights off, I can see backlight but no picture. Shining a flashlight on the screen does not reveal anything. Any thoughts? It is just a dark dimly lit screen no picture.

[Caleb]

Re: Toshiba 55G310U No Picture

You can check the fuse on the new tcon and verify it is getting power to the board, if you have a scope you can verify the lvds is making it to the tcon from the main board. I have never personally got a bad board from SJ but the law of averages says its possible.

[bwilliams60]

Re: Toshiba 55G310U No Picture

What kind of voltage am I looking for on the fuse. I assume it will be DC? I have an older scope and a PICO scope (laptop) but am unfamiliar with their use. Where would I hook it in to look for this signal. Can you be specific? I am fairly new to this but am fairly familiar with components and equipment. Just need practice. What am I looking for? Thank in advance for your help.

[bwilliams60]

Re: Toshiba 55G310U No Picture

I removed the TCON board again just to make sure it was seated properly on the four ribbon connectors and the two connectors at the bottom and they seemed to be okay. I found a connector to the TCON board a little out of its socket and pushed it back in and now here is what I have:
The screen lights up and the left half is like a light blue with darker horizontal and vertical lines through it. The right side of the screen is dark blue with lighter horizontal and vertical lines through it. If I press the input or menu button, it changes configuration a bit but still roughly the same. Thoughts?

[Caleb]

Re: Toshiba 55G310U No Picture

Now that you have something displaying on the screen you will want to unhook the ribbons from the tcon to the screen one at a time and see if you get a picture on either half. It sounds like you may have a fault on one side of the panel.

You should typically see about 12v on the tcon fuse, however some sets use 5v. The low voltage signal display should look like variable frequency square waves. However you may not be able to resolve them if you have an old slow scope. It may just look like digital noise instead, the main point is just to verify the main board is sending a signal to the tcon. now that you have something on the display the main is likely doing its job.

[bwilliams60]

Re: Toshiba 55G310U No Picture

Can you tell me where I would hook the scope in for this exercise? Also, is it possible to use this Picoscope or will it cause problems? I have never really used a scope except on vehicle ignition systems but would really like to learn how to use it for electronic repairs. Thanks for your help

[Caleb]

Re: Toshiba 55G310U No Picture

Along the ribbon connector from the main on the tcon board will be several signal lanes, as well as 2-3 lines of DC power and usually ground. I've never tried a pico scope before, I use a 250 MHz tektronics analog scope. Probe each of the pins looking for signals. It might be good to use a very fine point probe so as not to slip and short out the circuit. Did one side of the screen come up with the other side unhooked?

[bwilliams60]

Re: Toshiba 55G310U No Picture

The whole screen has lit up but I have not removed the ribbons. There are four all together across the top. Do I remove two at a time, one at a time? There are also two connectors at the bottom from the main board. Are these the connectors I am searching for a signal? I would presume so. When I ma checking for power at the fuse, am I using chassis ground or ground on the power supply low side connector?

[Caleb]

Re: Toshiba 55G310U No Picture

If you have 4 ribbons across the top I would remove two at a time (when Tv is unplugged).

Yes you would look for signal across the connectors on the bottom. I would remove the ribbons first as I think it is likely a panel fault, and you may hose up your new tcon if you slip the probe, use chassis ground for scope ground.

[bwilliams60]

Re: Toshiba 55G310U No Picture

I have attached three pictures. The first one is with all ribbons attached and has changed since the last time I turned it on. The second one is with the two left side ribbons disconnected only (facing the rear of the set) and the third one is with the two right side ribbons disconnected only.
If this is a panel problem, could you explain to me what the pictures mean and if there is a way to verify the diagnosis. (Just for learning purposes).

[bwilliams60]

Re: Toshiba 55G310U No Picture

Anybody have any ideas? I'm stuck at this point. What do these pictures mean?

[budm]

Re: Toshiba 55G310U No Picture

I say bad panel.

[bwilliams60]

Re: Toshiba 55G310U No Picture

Okay, I can live with that. Can you explain in more detail for those of us just learning. Much appreciated if you could.

[budm]

Re: Toshiba 55G310U No Picture

Training manual.

[bwilliams60]

Re: Toshiba 55G310U No Picture

Sorry, I'm still a little confused. Is there no concrete way to diagnose this such as a voltage check or waveform patterns than can be looked at. This article almost sounds like you have to make a leap of faith and replace the panel. I don't think I want to go there just yet.

[Caleb]

Re: Toshiba 55G310U No Picture

Does your tv have a small circuit board bonded to the ribbons along the top of the panel or do the ribbons feed directly into the panel? If the ribbons are directly bonded chances are high it is bad panel driver or tab bond failure, if it has the board across the top it may have a bad replaceable component on the board (still considered bad panel as they never intended anyone to try to work on it).

I haven't ever tried checking signals out of the tcon, but in theory it should be possible. From the training manual-
"Do not attempt to check for data or voltages on the LVDS connector at the TCON. This advice has been circulating around and is not recommended. In Figure 4 a picture of the LVDS connector is shown. In order to take a reading from one of the pins, you must insert your probe between a narrow area that is shielded and at ground potential. Several of the pins contain B+ for the TCON and panel. It is very easy to short one of these pins to ground and if it is a B+ line it is guaranteed you will be replacing a B board whether or not it was the original cause of the problem."

I think the only concrete way to know for sure is to swap your boards into a known good panel.

[bwilliams60]

Re: Toshiba 55G310U No Picture

Caleb, thanks for your input. I work in the motive power field and mostly on DC. I am not accustomed to parts swapping although the younger generation is getting very good at it. I like to have concrete proof that something is bad before I replace it. The TCON board was bad because I could visually see it burned through as you can see in one of my earlier posts.
I was watching a Youtube video from Grants Pass TV Repair that showed him using freeze spray on the connections around the outside of the panel. Some TV's would start to work properly if only for a moment to prove the bad connection theory. I have read also about the LVDS connector and to stay away from it. I would think you could go further into the board somewhere safely but this is my first run at television repair so it is all new to me. Just thinking about it as a hobby and make a few bucks on the side. I am getting some good lessons from this unit and even more from guys like you so I thank you and the rest of the guys who respond on here.
Any education is good education!

[Caleb]

Re: Toshiba 55G310U No Picture

This is indeed a very good place to learn, I am a lineman and very familiar with electricity but tvs are a very different animal. I picked up my first broken set about 5 years ago, and have learned a ton since then. I wouldn't count on making much money as the resale market is in the toilet with all the low cost tvs available. I put most all the money I make back into tools and test sets.

Once you understand the basic trouble shooting steps about half the repairs are very easy, but every now and then you will get one that despite your best efforts will not work. I have about 4 of these in the garage awaiting my skills to improve to the point I can fix them. I hope you have lots of room to store broken tvs and an understanding wife. If you like puzzles tvs can be extremely addictive.