Akai LCT3201AD Screen Darker on Right Side

[YamahaFreak]

This is a weird one, folks. I was paid to repair the backlight (bad caps), but once I was all lit up again, I now notice that the right hand side of the screen is slightly (noticeably) darker than the left side. There is a gradual gradient from light to dark, with no bars or bands. Also, the darker the displayed image is, the more dramatic the difference between the two sides. I'd think this rules out issues with the panel or the T-Con board, so I'm left to contemplate the inverter board. I must have replaced two dozen caps in this thing, between the power supply and the mainboard (anything that looked remotely suspicious) so I can't think of any other place to point the finger. I have attached a photo so you can see the issue. I have been all over the Internet looking everywhere for answers, but this doesn't appear to be a common anomaly. This one has me stumped!

[YamahaFreak]

One more image, for verification of the problem. (The Super Mario Bros. Super Show, heh! )

[CoogarXR]

I would vote for the inverter circuit as well.

I know from my test inverter that I use to test CCFL tubes, you can connect one side of a CCFL tube and get half the tube to light. This makes me think that in your case, the right side of your bank of tubes has an open. It depends on the type of inverter/tube set used, where you might find your open, but that's my guess anyway. It's weird that it stays running like that. It must "think" everything is OK...

[YamahaFreak]

Originally Posted by CoogarXR

I would vote for the inverter circuit as well.

I know from my test inverter that I use to test CCFL tubes, you can connect one side of a CCFL tube and get half the tube to light. This makes me think that in your case, the right side of your bank of tubes has an open. It depends on the type of inverter/tube set used, where you might find your open, but that's my guess anyway. It's weird that it stays running like that. It must "think" everything is OK...

I was thinking along the lines of one side of the circuit on the inverter board being dead or weak. Do you think the problem is more likely the inverter or the tube array itself? In the latter case, I'd have no idea how to test/repair.

[dr.ido]

Disconnect the LVDS cable to the panel, but leave the inverters connected and power it up. Many panels are "white" when off so you'll just see what the backlight looks like. If the backlight looks even with no dark side it's not the tubes or the inverter.

It's hard to tell from the pictures, but I have had panel faults that look similar. It's is usually a tab bond failure. You can remove the frame from the front of the panel and carefully apply pressure to each tab while watching if the image changes. Shim the affected tabs to hold them in position. There are videos on youtube that explain it better. I don't consider it a "real" repair, but it can get some more life out of a panel that would otherwise be scrap.

[YamahaFreak]

Originally Posted by dr.ido

Disconnect the LVDS cable to the panel, but leave the inverters connected and power it up. Many panels are "white" when off so you'll just see what the backlight looks like. If the backlight looks even with no dark side it's not the tubes or the inverter.

It's hard to tell from the pictures, but I have had panel faults that look similar. It's is usually a tab bond failure. You can remove the frame from the front of the panel and carefully apply pressure to each tab while watching if the image changes. Shim the affected tabs to hold them in position. There are videos on youtube that explain it better. I don't consider it a "real" repair, but it can get some more life out of a panel that would otherwise be scrap.

Are the tabs the ribbon cables that I usually see at the top of the panel? I'm not familiar with the term.

[mstaton]

That Akai is just a rebadged Samsung. They have an extraordinary failure rate for panels. The screen will be somewhat dark with the cable removed but will give you an idea. Removing the cable may not allow the inverters to fire up, just depends on the design.

[YamahaFreak]

Originally Posted by mstaton

That Akai is just a rebadged Samsung. They have an extraordinary failure rate for panels. The screen will be somewhat dark with the cable removed but will give you an idea. Removing the cable may not allow the inverters to fire up, just depends on the design.

Are you sure it's a rebranded Samsung? The insides don't resemble any Samsung LCD I've worked on, and I don't see their name on the panel, or anywhere else. I've also never seen a Samsung LCD TV/DVD combo.

[mstaton]

Maybe its just the DLP's

[YamahaFreak]

Originally Posted by mstaton

Maybe its just the DLP's

As in, Digital Light Processing? I believe I have seen some smaller, older (2004-07-ish) Akai DLPs and even CRT RP sets that were Samsungs inside. The Akai 27-inch flat CRT in my parents' bedroom is a rebadged Samsung, as well.

[CoogarXR]

I don't think that Akai LCD is Samsung. I worked on 60+ of the LCT27xxx models, and they were all no-name guts.

[YamahaFreak]

A $10 replacement inverter board is on its way. Hopefully this solves the issue, but if not, I'll try the tab bond trick.

[dr.ido]

There are tabs at the top of the panel. They aren't really ribbon cables. They are pieces of flexible PCB that contain the a driver IC. One edge is bonded to the panel itself, the other edge to the PCB that the flex cables from the TCON connect to.

Some panels also have tabs on the sides that contain driver ICs, but these are usually only connected to the panel on one edge. I've only seen a PCB on the some early panels.

[YamahaFreak]

Well, I tried fiddling with the tabs - no difference. Oh well, the customer is happy to have a working picture, so a happy ending after all.