Samsung LE46N87BD TCon problem?

[mick1992]

Hi Guys, new here, Im an Australian currently living in Germany.

Need some help with my Samsung LE46N87BD 46" LCD (its a European model, and the TCon is a AUO T460HWO2). I bought for 30 bucks, the guy I bought it off said it wasn't turning on so thinking it would be an easy fix (cap's) I went ahead and bought it.

Got home, plugged it in and it turned on but the screen was completely covered in different coloured vertical lines. (pretty sure the guy knew about samsungs dodgey caps and swindled me knowing it was something else)

Caps look good, TCon and main board show no visible signs of damage, burn marks ect. Have not checked voltage outputs yet as I don't have a meter at the moment.

Anyway I tried giving the lvds connector a wiggle, disconnected and reconnected while the tv was on with no luck. (LVDS cable from main board to tcon on this model is made up of normal wires and not a ribbon)

When the cable is disconnected the screen goes black and when reconnected the coloured lines come back but slightly different.

Removed the TCon and reflowed it in my kitchen oven, 10 min @ 200 celcius, and used some contact cleaner on the LDVS connectors and the connectors for the ribbons coming from the panel.

Now I have a completely white screen but if I wiggle the LDVS connector on the Tcon I can sometimes see the menu although its distorted now with vertical and horizontal lines. When I find the sweet spot and see the menu it will only last a minute or 2 before fading away to a white screen again.

The thing that worries me is when I have the distortion and can make out the menu, then start pressing on the ribbons where they connect the the sub boards sometimes the picture will change getting slightly better or worse.

Does this sound like typical TCon board symptoms, a power problem or is there a possibility the panel is defective?

I have ordered a new TCon and some 1000uf caps (going to re cap the power board anyway) and will post an update on how they go but I am still hoping you guys with more experience can share your thoughts...

[mick1992]

Re: Samsung LE46N87BD TCon problem?

OK quick update, so took another look at the TV, when the TV is cold I can see the menu and vertical/horizontal lines, lasts about 2 minutes then fades away to a solid white screen. Here are some pictures.

[ReeceyBurger123]

Re: Samsung LE46N87BD TCon problem?

Tab bond issue.

[Andrew F. Ali]

Re: Samsung LE46N87BD TCon problem?

Yes looks like the X-Source Tab signals not reaching the Y-Driver Tab bonds.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

Is this repairable?

[mick1992]

Re: Samsung LE46N87BD TCon problem?

OK guys so here's the thing, I'm a mechanic by trade, and I have some experience repairing circuit boards with normal sized components, but this is my first time repairing a TV. It only cost me 30 bucks, so if I can't fix it its no big deal but I want to give it a shot.

I have access to some soldering equipment, I don't have a heat gun type solderer but I do have a normal "hairdryer" type heat gun with an attachment nozzle that has an outlet about 8mm wide, its a good one from Mercedes with a digital display and I can set the temperature anywhere from 100-500 Celsius and fan speed too.

If you guys could walk me through repairing this with what tools I have it would be greatly appreciated. If I have to purchase a few parts its no big deal but I would like to give it a go without buying a complete electronics workshop.

Like I said if it doesn't work its no big deal.

Really appreciate the help.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

OK, capacitor's arrived today, TCon arrives in a couple of days, when these are installed if the picture is still messed up I will try some thermal pads on the panel ribbons.

Will keep you updated, if there is anything else you guys come up with please let me know.

[Andrew F. Ali]

Re: Samsung LE46N87BD TCon problem?

with the original T-CON Bd connected, turn on thr TV and measure these voltages on the T_CON Bd : (Be careful of probe slippage)
1. VON (VGH, VGON, VDDG) expected voltage 20V~30V
2. VOFF (VGL, VGOFF, VEEG) expected voltage -5v~-8v
3. VDD (VLOGIC, Vddd, Dvdd) expected voltage 3.3V
4. VDA (Avdd, Vdda, V source) expected voltage 13V~20V

If these 4 voltages are within spec the T-CON is good.
Look on the SOURCE (X) Bd/s (the thin one/s at the bottom where the FPC Tabs connect on to the Panel for the following signals:
VOFF, CPV1, VON and VCOMV1
Look on the DRIVER (Y) Bds on the left or right side of the panel (No DRIVER Bds??)
Then look on SOURCE (X) Bd/s again for another set of signals as follows:
STV, CPV2, VST1 and VCOMG2.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

Ok so when I check these voltages I should have the negative grounded on the chassis and use the positive probe on the board, correct?

Panel doesn't have driver boards on the side, only 2 boards along the top. It does have some things that look like ribbons on the sides of the panel but aren't connected to anything. When testing the 2 boards on the top what voltages should I be seeing?


I will grab the multimeter from work tomorrow and check these, then post an update.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

OK update

Voltages on TCon
12v IN - 13.5v
GAVCC1 - 3.3v
COM2 - 10.5v
VCC - 3.3v
COMF2 - 10.5v
AVDD - 15.5v
AVDD1 - 15.5v
VCOM2 - 10.5v
VCOMF2 - 10.5v
AGMODEN - 3.0v
VGHC - 28.2v
EXWP - 3.2v
VED5 - 2.4v *** is this supposed to be 5v???
VED3 - 3.2v

Source board voltages
Right side
AVDD - 15.5v
V3D3 - 3.3v
XVCOM - 10.5v
COMF2 - 10.5v
VGL - 5.9v
VGHC - 28.2v
COM - 10.5v

Left side
YVCC - 3.2v
V3D3 - 3.3v
XVCOM - 10.5v
LPC - 3.3v
MODE - 3.3v
AVDD - 15.5v
VGHC - 28.2v
COM - 10.5v

Could not find the STV or CPV points anywhere, maybe they are listed as something else or maybe I missed them, have attached photos.

Starting to think this might be a tab bond issue, or maybe both a tab bond issue and TCon issue at the same time.

Noticed some weird stuff going on, I was using a normal bedside light with an incandescent globe in it for light, with the light next to the TV turned on most of the screen was green and I could not see any change when pressing the menu button, then when I turned the lamp off the screen went back to being all messed up again and I could see the menu like in the PIC from my previous post. While the TV was like this the tabs started getting hot to the touch then the screen would do the usual and fade out to a blank white screen. Funny thing is while the screen was white if I turned on my lamp the screen would turn green again and the tabs would cool down. The electrical interference is doing something funny here and it has me curious, could someone explain exactly what is happening here?

[mick1992]

Re: Samsung LE46N87BD TCon problem?

The horizontal lines you see in the photos of the screen are from interference from the camera and not showing on the screen itself. You can use the picture of the green screen for reference, this was solid colour with no horizontal lines

[mick1992]

Re: Samsung LE46N87BD TCon problem?

.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

UPDATE!
New TCon and I now have solid picture!!!!!!!!

Now to the next problem.....
Picture is washed out and ghosting (see pics) settings don't change the picture at all (contrast, brightness ect)
What could cause this? Maybe I need to update the firmware?? (TCon is the correct part no. ect. but it came from a different model TV)

Also I have 2 solid white vertical stripes on the left side of screen, I'm guessing the tab bonds are causing this, but applying pressure to the tab bonds or the small chip on the tabs doesn't change this at all.

My question is; can the anisotropic conductive adhesive be reworked? And what temperature do the manufacturer's use to apply the adhesive??

My plan is to use a large "bulldog clip" to apply even pressure on the connection then using my heat gun warm it up to the correct temperature then let it cool to basically re work the connection.

When this fails plan B is to heat the adhesive, remove the tab, clean and re apply with some 3M 7303 aniscopic tape using the same method with the bulldog clip and heat gun to cure it.

Any help and advise is welcome and much appreciated!!

[vinceroger69]

Re: Samsung LE46N87BD TCon problem?

retest the t con voltages again just in case its faulty in someway.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

OK, Will test again tomorrow, need to get the multimeter again.

[vinceroger69]

Re: Samsung LE46N87BD TCon problem?

This thread has some good videos regarding faults etc
http://deboj.net/topic/samsung-led-t...lack-un60.html

[mick1992]

Re: Samsung LE46N87BD TCon problem?

Another update:

Looks like the original TCon has been reworked by the guy I bought the tv from, it has an R5101 gamma IC....

The new TCon has an AS51-F.

So I'm going to go ahead and order a new IC and fit it to the new TCon board. I will test the VGMA voltages before ordering to be 100% sure but after doing some research I have a strong feeling this is what is causing the screen to be washed out and lacking colour.

If this solves the problem then all that's left is 2 dodgey tab bonds causing the 2 white stripes on the left side of the screen.

For anyone who's interested, I have been thinking about this tab bond problem quite a lot and I have a new Idea to fix this (hoping the bad connection is on the board side and not the panel side of the tabs).
Did some research and found out the ACF bonds are cured at 180° Celsius for 15-25 seconds with pressure. So I'm thinking large bulldog clip with a strip of thermal pad along the edges preheated in the oven to 200° celsius then clipped onto the bonding area and left for about 20 seconds then removed.
Hopefully this will re-bond the tab, and I think it will be better than clipping it on first then applying heat because this way your getting instant heat and pressure in a similar manner to the proper machine, the thermal pad will transfer the heat better and the heat will be localised to the bond so your not risking unsoldering and nearby components. Will also need a thermometer and heat gun, checking the temperature and heating it more if it starts to drob below 180° during the 20 second period. (This is assuming the original ACF adhesive can be reworked *fingers crossed*)

So long as the bad connection is on the board side and not the IC or panel then even if this doesn't work I think I have a pretty good chance of replacing the ACF film, the pins on the board side are quite large compared to the panel side and I could easily align them with just a magnifying glass, probably even with the naked eye.

Once again any help and advise is welcome and appreciated!

[Andrew F. Ali]

Re: Samsung LE46N87BD TCon problem?

If you pull out/disconnect one side of T_CON to panel...do yo get good picture with one side, either left or right, disconnected?

[mick1992]

Re: Samsung LE46N87BD TCon problem?

OK guys another update...

Measured the VGMA voltages and entered them into Tom's Spreadsheet, and got a fail on gamma monotonicity and gamma symmetry.

Before I order the replacement gamma IC I need some advice!

With the left driver board disconnected from the Tcon I can still see the 2 big vertical stripes on the left side of the screen (see pics).
Does this mean the panel itself is damaged, or the IC to TAB bonding has failed or is there a chance it could still be the TAB to driver board bonding?
(I noticed one pin on the driver board looks burnt out and was wondering if this could cause symptoms even when the driver board is not connected) See pics.

And again help and advice is appreciated

[mick1992]

Re: Samsung LE46N87BD TCon problem?

This one pin definitely looks shot! It runs to the VGHC test pin from what I can tell.

Can someone please explain to me what VGHC is and could an open circuit here be causing my vertical stripes?

(The stripes are on the far left and the damaged pin connects to the furthermost TAB on the left)