Samsung LE46N87BD TCon problem?

[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)

[mick1992]

Re: Samsung LE46N87BD TCon problem?

OK this is more or less a bump up as I was dropping down the list and I have a feeling many people don't really look past the first page.

Really need some help here

What job does the VGHC signal do?

If the VGHC signal doesn't make it to the driver IC would this show symptoms of a failed driver IC/ failed TAB?? (e.g. vertical black stripe approx 2 inches wide)

I have been searching for information on this with no luck, would really appreciate if a tech could explain what the VGHC signal does and how not having this signal reach the left most TAB could affect my display.

I really appreciate all the help I have received so far, just need a little more to reach the finish line

[waterstrider]

Re: Samsung LE46N87BD TCon problem?

howdy. the fault could be from a broken trace on the edge of the glass panel from the top board to the gate drive ICs. if there are flexi PCBs on the sides of the glass panel(gate drive PCBs with ICs underneath),you will see small round test points covered in green insulation. scrape them green insulation off the top of the dots. get a volt meter, and try measuring the prime voltages in the first gate drive test points/dots (mostly the one on the top) if they are all present. VGH, VGL, DVDD, VDDA, are the prime voltages on those gate drive PCBs. if one of them is missing, or too low, the images will appear weird, slow or delayed. and sometimes on first power on, an image will show up, then fade till the screen turns white.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

Here I have 2 photos, the first is from the flexible PCB on the top left side of the panel. The points on this is where I should check for voltages as you have described, correct?

The second photo is from the driver board on the top of the TV, where the ribbon coming from the panel connects. If you look closely you can see one of the pads the ribbon connects to looks burnt out, tracing this back along the board it connects to the VGHC test point.

So if I don't get a reading on the flexible PCB on the side of the panel that matches the reading obtained from the VGHC test point then this will confirm that the burnt out pad is in fact what is causing the problem?

[waterstrider]

Re: Samsung LE46N87BD TCon problem?

yes that is a possibility. but you can still fix this by jumping a very thin wire from the top PCB to the gate driver PCB, well if that VGH voltage is the one that is missing that is. try measuring first the prime voltages. test all them dots to find out if those voltages are there or not. if they are all present in the gate drive PCB, the problem is not there and also that indicates that the lines from top PCB to gate driver PCB are good.

[waterstrider]

Re: Samsung LE46N87BD TCon problem?

the picture on the left is the gate driver flexi PCB. and, the green insulation is underneath it. be very careful not to bend or stress it too much because it may cause bond to glass and COF bond problems. if you can remove the glass panel from the frame and do them voltage diagnostics with the glass panel facing down the table the safer.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

so VGH voltage is only for the gate ICs (attatched to TABs on the sides of panel) and not for the the ICs attached to the TABs along the top of panel?

would this cause vertical lines?

Or only picture distortion problems??

Sorry for so many questions, I am new to this.

[mick1992]

Re: Samsung LE46N87BD TCon problem?

here is a close up of the pad I think could be causing the problem. Sorry about the low res, took the photo with my smartphone with 6x zoom then zoomed in on that on the pc...

[mick1992]

Re: Samsung LE46N87BD TCon problem?

Bump......

What does VGH and/or VGHC stand for and where does the power go to, gate IC or driver IC?

[vinceroger69]

Re: Samsung LE46N87BD TCon problem?

VGH is positive/high gate voltage (Voltage of the High Gate)
http://tvrepairsolution.blogspot.co....lcd-panel.html