42" LCD Insignia - Sound but no picture repair.

[Mershwer]

Hello Badcaps fellows.

This is my first post here on this forum. I chose it as it seems to be the best put together and I see a lot of solid advice and information here. I'm looking for assistance in repairing my TV. it's an Insignia LCD NS-46L780A12, 120V~ 60Hz 250W.

The issue is that the TV comes on, (LED goes from red to blinking blue three times and then a solid blue) and then I can see the backlight come on, and have heard sound coming through speakers when I had the cable still hooked in. However, there is no image on screen, even if I use a flashlight in the dark room method. This makes me feel as though it's not the inverter board, so I ask you all, does this sound like a mainboard issue? all my research i've done thus far leads me to think it is, but as I'm not very familiar with the hardware I thought it best to ask before buying a new 140$ main board for this TV. Especially since it could very well be a plethora of different issues.

[budm]

Re: 42" LCD Insignia - Sound but no picture repair.

if you do have backlights but no pictures on the screen then you need to check the DC voltage on the SMD fuse (on the T-CON board) on the both ends with ref to chassis ground. The T-CON board is on the top center of the rear panel under the metal shield, it has two flat ribbon cables on the top and two muti-wire connectors on the bottom.

[audiofreak19]

Re: 42" LCD Insignia - Sound but no picture repair.

+1 to that.

[Mershwer]

Re: 42" LCD Insignia - Sound but no picture repair.

Roger that. I'll check the TCON board when I get off work. I have a voltage meter, but forgive me as I don't know how to check the voltage per se. I know to put black to ground and red on the solder/connection, but I'm not entirely sure which setting on my Meter to use.

What would a SMD fuse look like? I'm pretty certain i know where the TCON board is. I'll just need to take a metal panel off to get to it I think. What should the voltage be reading as for a normal working connection?

Thanks for the patience and quick responses. I'm glad I came to this forum.

[budm]

Re: 42" LCD Insignia - Sound but no picture repair.

Take the pictures of your meter and the T-CON board then we can tell you what to do.
One of these two should be your T-CON board:
http://www.shopjimmy.com/catalogsear...q=NS-46L780A12

[Mershwer]

Re: 42" LCD Insignia - Sound but no picture repair.

Philips LJ94-23325B (PNF10180) T-Con Board for 46PFL5706/F7 is what I found on the website you supplied. It's a perfect match for what's in the TV. Now that I've located it, where would I utilize the voltmeter.

[budm]

Re: 42" LCD Insignia - Sound but no picture repair.

Put all the board back in place, you can leave the shield off but make sure to use the mounting screws to hold the board in place.Set meter to 'DCV', turn on the TV, Black probe on the metal chassis, Red probe on each of the fuse F1 (White fuse with 3A on top) at a time, it should show around 12VDC on the both ends. Just be careful not to let the probe slip.

[Mershwer]

Re: 42" LCD Insignia - Sound but no picture repair.

I tested the 3A fuse and both sides came back as 12.1-3Volts.

[budm]

Re: 42" LCD Insignia - Sound but no picture repair.

That voltage is good.
To the left of fuse, you will see little test point silver dot which is labeled as VCC33, and if look more you will see more test points:
VCC12V, AVDD, VSS, VDD12_CORE, VDD12_LVDS.
Take the DC reading on all those points to see what you get.
Right now it can be bad T-CON or the main board is not sending the signals to the T-CON.

[Mershwer]

Re: 42" LCD Insignia - Sound but no picture repair.

Checked the voltage:
VSS (#1) : .578 - 007 photo
AVDD (#2) : 2.2 - 005 photo
VCC33 (#3) : 2.6 - 010 photo
VCC12V (#4) : 2.2 - 002 photo
VDD12_CORE (#5) : 2.2 - 013 photo
VDD12_LVDS (#6) : 2.4 - 014 photo

[bammbammfran]

Re: 42" LCD Insignia - Sound but no picture repair.

with it all connected
check to see if you have power at the top two flat ribbon connectors.
you will see a group of 3 or 4 pins near the end of the connectors that are grouped together on one board trace.
one group should be + and another is probably Ground

you can also check CON1 at those pins to see if you get signal voltages
every third pin is probably a ground, so you won't see power at all of them

[Mershwer]

Re: 42" LCD Insignia - Sound but no picture repair.

Bamm, could you be a bit more specific please? could you possibly use that voltagechecks1.jpg and highlight or circle the area/pins that I should check?

[tom66]

Re: 42" LCD Insignia - Sound but no picture repair.

Can you try measuring voltage across D11, near the fuse?

[bammbammfran]

Re: 42" LCD Insignia - Sound but no picture repair.

I can try

I do not know this panel exactly, so I am guessing on locations of power based on similar boards that I have played with
But
It looks like the two groups of pins that lead to C02 and C04 capacitors on the two top clips and which are circled in smaller blue circles should be the pins that power the lcd pixels

the red circled area at the bottom plug would be pins that get video signal from the main board. If signal is getting there, these will usually show a low voltage (possibly 2-3volts) . again, normally every third pin would be a ground.
the small yellow circle is a ground of pins that sometimes have 12 volts, but on this one, that may not be there since the 12 might only go through the other plug

you can also check for the top two voltages with the bottom CON1 disconnected. on some model displays, disconnecting this cable could cause a solid color test screen affect to show up on screen

[budm]

Re: 42" LCD Insignia - Sound but no picture repair.

Checked the voltage:
VSS (#1) : .578 - 007 photo
AVDD (#2) : 2.2 - 005 photo
VCC33 (#3) : 2.6 - 010 photo
VCC12V (#4) : 2.2 - 002 photo
VDD12_CORE (#5) : 2.2 - 013 photo
VDD12_LVDS (#6) : 2.4 - 014 photo

It looks like none of the buck regulators are working since you are getting those voltages in mV range. The main 12V feeding the circuit is not getting through some how.

[Mershwer]

Re: 42" LCD Insignia - Sound but no picture repair.

Budm, since there isn't any voltage going to those areas what does that mean? Does it show the TCON board is needing replacement, or perhaps lending to an issue with the mainboard and the power not going to the tcon? I'm sorry I"m kind of slow with all of this stuff guys. Kind of learning as I go. What should I be looking for from here on?

Bamm, I've checked the voltage in the areas you highlighted on the bottom and I was able to see 12v on a few, but I don't know what to do with that information or what it means. :/

Thanks again for everyone's help so far.

[bammbammfran]

Re: 42" LCD Insignia - Sound but no picture repair.

what is tough on these , is that it looks like it gets two separate signals from the main board. one from red to red and the other from green to green.
looks like power runs the dark blue line path and the light blue sends signal to the top connectors. so the power may not be powering on the dark blue area chips ??

try , for hahas , to check the voltages at the pins of the chips in the pink circles.
I think they are voltage regulators (part numbers on these might help to figure out what they are and what the outputs should be and if there may be an issue there ???

[budm]

Re: 42" LCD Insignia - Sound but no picture repair.

You can take a chance and spend about $25 on the board.

[Mershwer]

Re: 42" LCD Insignia - Sound but no picture repair.

Here's a photo of the voltages I got on the two pink circled areas. For the Shiggles. The one in the upper center doesn't have the 12V~ that the one on the left did. Would that mean that something is failed in that particular "chip"?


Is this TCON board something that, if replaced, would fix this issue hypothetically? Or I assume we're still in the troubleshooting/diagnosis stage? Sorry, haha, had a couple beers for a liquid lunch.

[budm]

Re: 42" LCD Insignia - Sound but no picture repair.

"Is this TCON board something that, if replaced, would fix this issue hypothetically?" I would say more likely due to all the voltage readings are way off, unless we have a person with another board that can supply the voltage readings for comparison.