T-Con repair help

[caphair]

32” LCD Tv has backlight but no display (sorry don't have tv in front of me for model number) but t-con seems to be the issue.

F1 is open, I measure 12v from connector side and 0v from other side. F1 measures open as well.

I tried powering tv on with my multimeter set to amps to bridge the fuse momentarily and see how much current flows so I could get an idea if the fuse happened to blow with no other issues, but when I do that the tv shuts off completely and needs to be unplugged for standby light to come back so I'm guessing if I replace F1 it would just blow again.

I don't measure any shorts at the board side of F1. Should I try running 12v into it and see if anything heats up?

[dskall]

Re: T-Con repair help

Did you try with cable disconnected from panel? What was your resistance measurement?

[caphair]

Re: T-Con repair help

Did you try with cable disconnected from panel? What was your resistance measurement?

Did I try what with cable disconnected? Resistance of F1 is OL open

[petehall347]

Re: T-Con repair help

you could try finding the short by checking from fuse to things like c21 c22 d2 etc .

[dskall]

Re: T-Con repair help

Did you try powering up with the panel disconnected from t-con?

[caphair]

Re: T-Con repair help

Did you try powering up with the panel disconnected from t-con?

No. Why what would this do?

[caphair]

Re: T-Con repair help

you could try finding the short by checking from fuse to things like c21 c22 d2 etc .

I have and nothing measures shorted

[petehall347]

Re: T-Con repair help

dskall is onto something .

[dskall]

Re: T-Con repair help

You can then eliminate bad panel or board from t-con. Check the current draw across fuse with cable to panel disconnected.

[caphair]

Re: T-Con repair help

You can then eliminate bad panel or board from t-con. Check the current draw across fuse with cable to panel disconnected.

Ok what am I looking for when doing this?

[NeedsMoreFlux]

Re: T-Con repair help

I think what he is referring to is: disconnect one side of the ribbon cable and see if you get a picture on one side. Then try the other side.
If you are a noob show pictures and tell us where/what you tested, specifically.

You should see where the cables plug into connectors from one board to the other. there will be voltages listed. most times the t.v.s metal body can be used as ground.

Let us know...

Oh, and if you can't post pics: put them on your comp.
Right click, and select "edit."
It will open in Windows paint.
Select "Resize" on the top left.
Resize it to 2000x2000 pixels or lower, and make sure the picture is under 2MB.

[caphair]

Re: T-Con repair help

I think what he is referring to is: disconnect one side of the ribbon cable and see if you get a picture on one side. Then try the other side.
If you are a noob show pictures and tell us where/what you tested, specifically.

You should see where the cables plug into connectors from one board to the other. there will be voltages listed. most times the t.v.s metal body can be used as ground.

Let us know...

Oh, and if you can't post pics: put them on your comp.
Right click, and select "edit."
It will open in Windows paint.
Select "Resize" on the top left.
Resize it to 2000x2000 pixels or lower, and make sure the picture is under 2MB.

There’s only one cable per connector on the t-con (one from mainboard to t-con and one from t-con to panel) and the fuse F1 is open so how would I even try to get a picture through the t-con board?

[diif]

Re: T-Con repair help

Every t-con I've found with a shorted fuse, has just had the fuse replaced and the TV has then worked. If there's no short between the 12v and ground then replace the fuse and see what happens.

[caphair]

Re: T-Con repair help

Every t-con I've found with a shorted fuse, has just had the fuse replaced and the TV has then worked. If there's no short between the 12v and ground then replace the fuse and see what happens.

Ok but why when I used the meter in amps mode to act as a temporary bridge across the fuse the tv shuts down?

[diif]

Re: T-Con repair help

Ok but why when I used the meter in amps mode to act as a temporary bridge across the fuse the tv shuts down?

Perhaps there actually is a short in the tcon you've just not measured it correctly. If there is a short, bridging the fuse is a bad idea.

[caphair]

Re: T-Con repair help

Perhaps there actually is a short in the tcon you've just not measured it correctly. If there is a short, bridging the fuse is a bad idea.

I tried running 12v through the tcon from the fuse end and only FL1 got hot but that just looks like a ferrite bead filter so it would just draw current with no resistance right?

Also noticed when injecting 12v the voltage dips down to 5v and full amps goes though

[diif]

Re: T-Con repair help

Sounds like a short.

[Andrew F. Ali]

Re: T-Con repair help

Oh...Definitely a shorted T-CON Bd. The TV will shut down if it detects absent T-CON Bd as the fuse is open. This I found mostly with LG TVs.Re[place the T-CON Bd and your problem will be solved.

[momaka]

Re: T-Con repair help

Oh man, I did so many write-ups on T-con boards a while back, but it's going to take me a while to find those posts, so here goes a quick version of that.
.....

The T-con board for LCD TVs and monitors typically has 5 important voltage rails. These are:

1) Main supply voltage: typically 3.3-12V that comes from the power supply and/or logic board. On your T-con, this voltage rail can be found at test point VCC (right by fuse F1).

2) Main boost voltage: typically 12-15V, depending on the panel requirements. This rail is generated by a buck-boost converter from the main supply voltage rail mentioned above (VCC). On your T-con, this voltage rail can be found at test point VDD (below the 4 ceramic caps to the left of the top ribbon connector.)

3) Secondary positive boost voltage: typically 15-30V. This rail is generated by a charge pump circuit from the main boosted voltage rail (VDD). On your T-con, this voltage rail can be found at test point VGH (above ceramic cap C54 to the left of the top ribbon connector.)

4) Secondary NEGATIVE boost voltage: typically -5 to -10V. This rail is generated by a charge pump circuit from the main boosted voltage rail (VDD). On your T-con, this voltage rail can be found at test point VGL (right below the top ribbon connector.)

5) LVDS chip VCC: typically either 1.8V, 2.5V, or 3.3V. It is generated from the main supply rail (VCC), usually by a linear regulator or two (like 1117 or similar). On your T-con, this voltage rail can be found at test point VCC2 (all the way to the right of the picture, next to that SOT-223 regulator with PCB designator "US2".)

.........
So the way I would attack this problem (blowing fuses on T-con board) is by first measuring the resistance from each of those test points above to ground. Anything with less than 100 Ohms resistance indicates a possible short-circuit, and anything with less than 50 Ohms (especially VDD, VGH, and VGL) is quite likely to be a shorted or partially-shorted ceramic cap.

But for starters, post what resistances you get. Also, take two sets of measurements: one with the LCD panel cables connected, and one with those cables disconnected. As dskall tried suggesting above, we want to see if the panel is causing the short-circuit or not.

[dskall]

Re: T-Con repair help

momaka I copied above post for future reference.