Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshooting

[omegastrm]

Hi everyone, I took upon a project, which is a stubborn Insignia NS-LCD32 that needs some professional attention. The story behind it is that the tv went through a thunderstorm and when the last owner tried to turn it would only show a green power light and nothing else.

Anyways here's the detailed rundown:
Pressing the power button makes power light go green, however the screen is blank and there is no sound even when I connect an HDMI device. Also to power the tv off and make the green power light disappear I have to hold the power button for approx 5 seconds.

Course of action:
First I checked the power supply and all voltage going out to the rest of the boards is correct so I'm pretty sure that its working fine.

Next I looked at the main board, however I'm not sure where to start and what to check on that. (I suspect there may be a problem with it because I believe it also controls the sound)

Then I moved on to the Inverter board. The one fuse that i found on it is fine, however the 5 of the 12 ballasts (not sure if i am using proper terminology, but the mini-transformer looking things) apparently were bad. At first I thought that this could be the root of all problems, since the sole function of an inverter board is to power up the bulbs, However there are no cables that go from the inverter board to the sound, so I am wondering if the main board might also have taken a hit. In addition to this I would like to know if there are a total of 6 outputs that power the screen and if say 2 end ones and 1 middle ballast/mini trasformer does not work, should the other bulbs light up, or do they follow a series circuit in which if one goes out, then all of them go out. If I was an engineer I would have made it easier to distinguish and put them in parallel so that if any one of the mini transformers failed, one light would go out, while the others would remain working.


Then on to the T Con board. I don't have a clue as to what to check on here, but i don't suspect it to be a problem because like i mentioned earlier there is no image, light, or sound, which means that the t con board might not be problematic.


This is the best I could do and I appreciate any advice or help and guidance that would help me ID the problem and fix this darn thing.

Thanks to all responses in advance

[drpj23]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

Ok, if all is ok on the power supply, then it does sound like we have some problems on the main board and or inverter.

Main is responsible for sound/image processing/and cutting on the backlight.

Do you have an image on the screen via another source of light such as a flashlight?

The inverter board should have a connector with a legend by it, can you report those voltages? Mainly ones like BL_ON and ERR and DIM.

How did you find out that the transformers on the inverter boards were bad?

Since this was affected via a thunderstorm, it is possible your main was probably hit directly in some way via connections to it (like HDMI, RCA, etc.)

Anyways, as a help to all, please include high quality pic of the back of the tv, especially of the inverter board(s) and main board using the manage attachments feature.

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

I tried playing a dvd via standard a/v cables and got nothing, no sound (with headphones plugged in and without) or video.

When trying to shine a flashlight I do not get any image.

For the inverter board, I took the COM lead of my Multimeter to pin 8 GND and checked the rest of the pins (i am not sure if I did this correctly or not):

1 - vin - 23.7v
2 - vin - 23.7v
3 - vin - 23.7v
4 - vin - 23.7v
5 - vin - 23.7v
6 - GND
7 - GND
8 - GND (placed COM lead on this one while checking the rest of the pins)
9 - GND
10 - GND
11 - ERR - 0v
12 - ON/OFF - 0v
13 - PDIM - 3.2v
14 - NC - 0v

You asked how I determined that some of the transformers were bad and I did so by checking the continuity on each transformer through its various terminals. I included a continuity test result picture to show what I got.

I would like to test the output voltage that those little transformers give off, but I don't know what kind of high output it gives so I don't want to fry my multimeter by doing so without knowing.

[drpj23]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

Do not try to measure those transformer outputs - they are very high voltage and will damage your meter.

Well your reading on 12 indicates that the main is not cutting it on.
What is the panel model?

Start measuring the voltages on the pins of the voltage regulators. Report it by part name then each pin.

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

I am not sure what you mean by panel model and by voltage regulators do you mean the output on the pins of the power supply?

[drpj23]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

Sorry I wrote that in haste.
Panel model will be on a sticker on the back of the actual panel.

Well, for the HV transformers, you just need to test the top 2 pins and the 2 pins on the right (from my point of view of the pic). But if you say those are shorted, then those are indeed bad. Are both fuses good on the inverter board?

I suppose we'll work on this first before blaming the main for stuff right now.
0.0v ERR might be telling the main to shut off inverter.

[budm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

As drpj23 had indicated, the inverter board in not getting the turn on cammand signal from the Main board to turn it ON (Pin 12 ON/OFF of the Invreter board shows 0V as you have indicated, it shoul have around 3~5Vdc).
You should verify that pin by disconnecting it from the inveter board and take the voltage reading of pin 12 again to see what you have.
You can also try turning it by disconnecting just the pin 12 (you have too, otherwise you will back feed the voltage to the main board) and then use 1K resistor hook up between pin 12 in the inverter board and the 5V pin of the power supply board, turn the TV on, if the inverter is OK, the lamps should light up.

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

Thanks for your response & help guys! I very much so appreciate your aid. I haven't been able to find the time to sit down and do some more troubleshooting of the tv, due to work and all, but I will probably have some time before this weekend to do so and give you guys a further update.

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

Budm can you explain the reason behind using a 1k resistor hook up between pin 12 in the inverter board and the 5V pin of the power supply board? Why can't I just use a regular wire and solder that from the pin 12 connection to a 5v pin from the power supply board?

[budm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

The resistor is used to limit the current feeding the transistor so it will not destroy the transistor, with 1K resitor, max current will be limited to 5mA (5V/1K = 5mA)

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

Thanks for the explanation.

follow up:
I cut into pin 13 PDIM 3.2v wire and soldered one end of the 1k resistor to it and then I cut the pin 12 wire. I wrapped the end coming from the power supply with electrical tape and took the other end of the wire feeding into the inverter board and soldered the other end of the resistor to it. The whole screen lights on with a greyish tint. I can't turn the tv off by pressing the power button or using the remote nor does pressing the setup and menu buttons on the side of the tv do anything.

[selldoor]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

pictures are a bit out of focus for troubleshooting

"Then I moved on to the Inverter board. The one fuse that i found on it is fine,"

but i think there are two white fuses near the big connector in the top middle.

Probably ok as the lamps lit - also if they all lit that does mean the inverters are ok or did you replace already

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

i'm not sure if all the lamps were lit though. Also i wasn't able to get into menu screen or change channels or change volume or power it off using the buttons on the side or the remote.

the two white fuses on the inverter board are good. both showing 00.5 ohm

I attached a clearer pic of the inverter board.

[budm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

It sounds to me that the power supply and the inverter are OK since the lamps stay on, since you are seeing just the glowing screen and the main board also is not sending the bl_on to turn on inverter (but you van force it on) so the problem you are having is on the main board.

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

man these main boards are expensive...$80 to be exact. Any advice on how to further isolate the problem in the mainboard? (if it is feasible of course)

[budm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

Insignia uses the same base model number and follow the model number with the dash and number for the year, I.E. Insignia NS-LCD32-09 for 2009 model. What is your complete model number? We will need to find the service manual to troubleshoot the main board.

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

its a November 2007 model. It's NS-LCD32
There is no -09 or -07 after it. I've found the service manual for the 2009 model, but I can't find anything for this year.

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

Update:

I bought a replacement main board from online, however the problem was not fully resolved. The tv can now power on and off, however I am getting a grey screen upon powering on.

I am starting to wonder if there is a problem with the T Con board also.

What kind of voltage should the T Con board be getting?

[budm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

The DC for the T-CON will depend on the LCD panel spec, it is either 5V or 12V, you can check the voltages at both ends of the fuse on the T-CON board.

[omegastrm]

Re: Insignia NS-LCD32 powers on but blank screen & no sound, need help troubleshootin

i bought another used t-con board for it now....SAME DARN GREY SCREEN >:/

I'm going to check voltage and connection to every board right now

what else can it be?????