Samsung LNT4661fx/xaa

[landyboy]

Picked up a Samsung with power issues. Replaced several bad caps on power supply, now it powers on but I get this (see pics). I have pressed all around the screen and I don't think it is a tab bond issue. Could this be a bad TCON?

[landyboy]

Re: Samsung LNT4661fx/xaa

Or possibly a bad main board?

[landyboy]

Re: Samsung LNT4661fx/xaa

Ok i replaced the TCON today and no change. Some observations I have made: Most white colors or ok seems to be only dark images. Could a bad main cause this?

[landyboy]

Re: Samsung LNT4661fx/xaa

I also have tried the AVI inputs with the same result.

[Glitcher]

Re: Samsung LNT4661fx/xaa

Bad panel, I had the same model with the exact same problem. I replaced a known good tcon and afterwards it played 4 inch vertical bars so put back the old one. I'm guessing the old tcon board had something shorted in it which let it at least play a picture but with that dark contrast instead of bars.

[landyboy]

Re: Samsung LNT4661fx/xaa

Haven't worked on this for a while but I came across another mainboard and tried it now the picture has changed but is still bad. I don't disagree that it maybe a bad panel but I thought I would try a different main.

[Shinju]

Re: Samsung LNT4661fx/xaa

panel adjustment in the service menu.

TV off, MUTE and press 1 8 2 and power on the remote.

There should be a setting in Option Byte with the LVDS options PDP, JEIDA, VESA. (also make sure to have something playing in the background on HDMI 1) helps you see the changes made if any.

write down your settings before changing anyting once you change something you cannot go back (factory reset) you are programing your panels EEPROM. If you go back and set it to what you had before that will work.

If the VESA deal doesn't work try changing the panel type if you can.

[budm]

Re: Samsung LNT4661fx/xaa

Boy, another with bad setting in the service menu? Shinju already helps fixing the other one with similar issue.
https://www.badcaps.net/forum/showth...387#post470387

[landyboy]

Re: Samsung LNT4661fx/xaa

Ok was able to get into service menu. Got to the option Bytes but the LVDS had only two settings that you could adjust Lvds Tx Fmt and Lvds Tx Bit. I did try different setting in each and the picture would change but was never correct. I also tried changing panel type with the same results. I did this with both mains I have the original and the one I just bought (could be bad also) I checked panel hours and with original board 12k 7k with board I just got.

[landyboy]

Re: Samsung LNT4661fx/xaa

Option Byte Menu

[budm]

Re: Samsung LNT4661fx/xaa

I am still curious about this kind of symptom, can you please take the GMA DC voltage reading of the test points on the T-CON board for me?
Never mind, the on screen menu looks normal.

[elltee]

Re: Samsung LNT4661fx/xaa

Hi landyboy, have you repaired this tv? Was it the panel ? I have the exact same model, after changing the caps on the power supply it comes on showing pretty much like yours. I managed to get more brightness by adjust subrightness and subcontrast in the service menu, but still looks like crap.Right side of the screen looks brighter than the left side.

[neilc6]

Re: Samsung LNT4661fx/xaa

Have this model of tv with the same problem. Dark and very red. There were pink dots before. When I opened it up, I noticed some caps had been replaced and appeared to be the correct values. I did a reset in the service menu and it brightened things up and cleared the pink dots. Found VESA in the service menu and changed panel type with no improvement. I will check the gamma voltages in the tcon next.

[neilc6]

Re: Samsung LNT4661fx/xaa

A little further testing indicated the TV had trouble starting when plugged in. Took 3-4 restarts. Measuring the replacement caps, they were a bit low and had high esr. Replaced them and tv turns on right away and no pink dots. Still dark and red. Color seems off in the menus as well.

Checked tcon gamma voltages and they seem ok as well. From 1 to 18: 14.91, 13.89, 11.96, 11.39, 10.85,10.49, 10.25, 10.18, 8.85, 6.53, 5.47, 5.28, 4.97, 4.48, 3.83, 3.28, 1.33, 0.33

Service menu shows TULIP panel 46CMO panel type.

[freakaftr8]

Re: Samsung LNT4661fx/xaa

That's a sharp decline between 8.85 and 6.53 and also 3.28 to 1.33 seems like a sharp decline also.

Could be a cause to your dark and red problem. I would make sure that your LVDS cable is clean

[neilc6]

Re: Samsung LNT4661fx/xaa

Here are the pics. Tcon is LJ94-01904E or BN81-01312A according to Shopjimmy. Guess it's very red or very blue depending on scene. Not sure if I want to gamble replacing the tcon.

[freakaftr8]

Re: Samsung LNT4661fx/xaa

That looks like a gamma problem to me. Let's see what others think.

[budm]

Re: Samsung LNT4661fx/xaa

GAMMA Voltages problem to me.

[neilc6]

Re: Samsung LNT4661fx/xaa

I ordered a used tcon on ebay. Just a bit of a gamble since the seller indicates they will take returns. Will report back once I get it in and will also post the gamma voltages on that board as well.

[neilc6]

Re: Samsung LNT4661fx/xaa

Used tcon on ebay arrived, I installed it and picture is normal. Looks like the big drops in gamma voltage were causing the color issues. I put the shield on and don't want to take it off again to remeasure the voltages. Thanks freakaftr8 and budm for the correct diagnosis.