Backlight, no picture Insignia NS-37D20SNA14

[Spork Schivago]

Hello,

A customer brought me an Insignia NS-37D20SNA14 today. He said he replaced the inverter board and it worked for a bit but now it's back to no picture. I highly doubt he actually replaced the inverter board because it's an LED TV. I think he might have meant he replaced the T-CON board.

Normally, I'd test the T-CON by hooking up a video source and seeing if there's sound but no picture. The backlight turns out, I've checked the voltage sources coming from the PSU, they appear to be good. There's two 12V and then a BOM and a PWM. Not really sure what the BOM and PWM should measure, but I get voltage when I turn the television on.

Anyway, does anyone have any suggestions on how to test the T-CON board? When we moved into the new house, we got new DVRs from the local cable company. They don't have coax output, just HDMI. We currently have no devices that in the house that have coax output.

I'm thinking by default, the television (because it's been without power for a while) would turn on and look for a video source on coax, not HDMI or RCA (the yellow, red, white cables). I'm tempted to try RCA because we have RCA outputs and then just mess with the video input button to see if we get any sound.

Is anyone familiar with this television? If so, any ideas what I should look for on the T-CON board or how to go about testing it with a multimeter?

Thanks!

[petehall347]

Re: Backlight, no picture Insignia NS-37D20SNA14

probably changed power board .
if i am thinking right a hdmi input should switch automatic ,,may be wring though depending on the set .
first check with a lamp pointed at the screen to look for a picture saying no input or something . like you do .

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

Petehall347, thank you for the response. Could you elaborate on the purpose of the lamp? The backlighting is working. The LEDs do light up.

I don't think he replaced the power board. He said the symptoms are the same now as they were before he replaced the "inverter". I would have thought a bad power board would mean no backlighting.

I will try hooking an HDMI cable up to the set and see if I get any sound.

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

I hooked the HDMI cable up to HDMI port 1 and then HDMI port 2 (there's two HDMI ports). Nothing. I hit the Input button a bunch of times, still no sound.

[petehall347]

Re: Backlight, no picture Insignia NS-37D20SNA14

ah i thought no back-light .. so supply powers everything .. if ok it narrows it down a bit ..
main board tells tcon what to do .tcon tells panel what to do .
sorry i am almost asleep and been on the pop ...

[nwcs]

Re: Backlight, no picture Insignia NS-37D20SNA14

If you press the menu button do you get anything on the screen?

[diif]

Re: Backlight, no picture Insignia NS-37D20SNA14

Do you get 12v on the t-con ?

[budm]

Re: Backlight, no picture Insignia NS-37D20SNA14

Do you get 12v on the t-con ?

+1, at both ends of the SMD fuse.

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

Okay, I am sooooo sorry guys, I am such a freaking idiot! My friend Paul came and when I was talking to him, I was looking over the board and noticed a header with no plug. I'm like I wonder what that's for, duh! The speakers!!! When I did the HDMI test, I didn't have any speakers plugged in!!!

So, I plugged in the speakers and tried again, I definitely have sound. When I press menu, there's no OSD. There's no picture, just backlighting.

I'm leaning towards T-CON. I found one SMD fuse on the T-CON. I didn't pull it but I put my meter on it and checked the continuity, 0 OHM. I'll check the voltage on both sides.

Diif, from BudM's post, I'm guessing I check for the 12v on that one SMD fuse? It's a fairly big fuse for an SMD component. I'm used to seeing small little ones. I can post clear pictures of the T-CON and logic board if you guys would like. If you want, I can post pictures of the front and back, or if you're okay with it, I'll just post pictures of the front, while it's still attached to the TV.

Let me know what you guys want me to do and I'll be more than happy to do it. I'm going to go check the fuse to look for the 12V and I'll report back in a minute.

I'm going to leave the HDMI cable unplugged when I check because my wife is watching TV. Thanks!

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

I get 12.30VDC on both sides of the SMD fuse. It's very close to the connector that's on the T-CON board. I believe it's the only fuse on the T-CON board. I could purchase a new T-CON board, but if this customer already replaced it, I'd like to think something is killing the T-CON boards and the fix probably won't last. I'd rather fix the T-CON than replace it. I feel I'd learn a lot more by fixing it.

After searching BadCaps.net, it seems this TV uses inferior caps. Would crappy caps on the PSU be something that could kill a T-CON board?

[budm]

Re: Backlight, no picture Insignia NS-37D20SNA14

OK, try having one ribbon cable between T-CON and the LCD panel connected one at a time to see if you see picture on half of the screen.
Then will need good clear picture of the T-CON to look for Voltage test points: VGH, VGL. VCC, VCOM, etc.

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

OK, try having one ribbon cable between T-CON and the LCD panel connected one at a time to see if you see picture on half of the screen.
Then will need good clear picture of the T-CON to look for Voltage test points: VGH, VGL. VCC, VCOM, etc.

Budm, the T-CON board is a HV365WXC-200. Here's a datasheet for it, although the datasheet I think might be for the same T-CON but in a different TV. http://www.datasheet-pdf.com/datashe....php?id=866502

I removed the right ribbon cable from the T-CON board. Then I turned on the TV, the picture was still all black on both sides. Then, I plugged it back in and removed the left and turned on the TV. The left half the screen was white.

After that, I noticed the ribbon cables each have a flip type connector on a long but not wide board that would be the top edge of the television. So, I killed the power and pulled each ribbon cable off those long boards and reseated them. I looked at both those long but skinny boards for fuses and didn't see any.

For shits and giggles, I turned the TV back on, and guess what? I see the Insignia Logo! Then I see the cable picture. So, I know reseating the ribbon cables on the T-CON board itself didn't fix the problem, I had tried that earlier. Either reseating the ribbon cables on those long skinny boards fixed the issue or the fix is temporary and there's a bad solder joint somewheres and when I removed them, I jolted it back into place.

Any ideas how to confirm the ribbon cables weren't properly seated? To me, I almost thought the left one wasn't properly seated, but that's the one that showed an all white on the left of the screen picture when I removed it from the T-CON part of the board. Any thoughts?

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

Our daughter's sick and because my wife's back to work, I've been getting up with her at night. Last few nights, I've only gotten 4 or 5 hours of sleep. I'm gonna head to bed and I'll read your response tomorrow.

I wanted to know what we were looking for when you had me remove the ribbon cables. What should we have expected to see and what might it mean if we didn't see that? I wanted to know so in the future, I know what to do and what to look for. Thanks for the help!

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

Should I also replace the capacitors, even though they're not bad? You know, take preventive measures? Thanks!

[vinceroger69]

Re: Backlight, no picture Insignia NS-37D20SNA14

have you still got a good reliable picture (few power on/off cycles during the day) did you clean the ribbon cable contacts? or just re seat them as the socket/contacts maybe a little dirty etc and the fault may reapear in time/use,regarding a recap i guess you mean the ones on the psu?

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

have you still got a good reliable picture (few power on/off cycles during the day) did you clean the ribbon cable contacts? or just re seat them as the socket/contacts maybe a little dirty etc and the fault may reapear in time/use,regarding a recap i guess you mean the ones on the psu?

I still have a good reliable picture. When it was on, I tried trigger the fault by moving the boards a bit, wiggling the ribbon cables, nothing happened, so I assumed it's fixed.

I just reseated the cables. There was no visible dirt and they looked to be in good shape. The left one had marks where the bar for the connector pushed it down, but I don't think this was the problem. When I removed the left one, it didn't seem like it was seated properly, but I thought maybe when I flipped the bar, I might have accidently moved the ribbon cable free a little. I really think this was the problem.

For the capacitors, I'm referring to the electrolytics on the PSU and the one electrolytic on what I call the logic board. It's the board that has the HDMI, RCA, coax, etc connections. I think there's a total of 10 caps. 2 are the big ones that every PSU I've seen have, and then 1 on the logic board, 7 more on the PSU.

[vinceroger69]

Re: Backlight, no picture Insignia NS-37D20SNA14

thats good the issue seems too be fixed now so yes as theres only a few capacitors i would replace them should be a good preventive measure but saying that the large primary ones are usually expensive and are a lot of the times ok so maybe discharge them and test esr/uf and if ok leave those two but its up too you on how much you want to spend on the set etc.

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

Up to the customer I guess. Would a good ESR and farad reading matter with low quality caps? For example, if the ESR is nice and low and the farads are within 20% of their stated value, but the cap manufacturer is garbage, should they still be replaced? Thanks.

[vinceroger69]

Re: Backlight, no picture Insignia NS-37D20SNA14

i replace known garbage capacitors i dont even measure them i just swop them when i see them fitted.

[Spork Schivago]

Re: Backlight, no picture Insignia NS-37D20SNA14

Okay. So with you, you don't even give the customer a choice, right? If you're getting paid to do a job and you know the caps are junk, even if they might not be causing a problem at the present time, you just replace them? That sounds logical.

I had a customer bring me a motherboard once that had bad caps. They looked like polymers but they weren't. They were actually electrolytic. I made the mistake of telling him he had two bad caps but I was going to recap the entire board. He didn't want he entire board recapped, just those two bad caps replaced.

I highly suggested against that but he insisted. I replaced them and got the board back, maybe a week later. At that time, I told him I was going to do the whole board. Again, he insisted on just the bad one. Third time, I just did the whole board. He spent more money on the three shipping charges and it wasn't really that expensive to recap it. Now, he says he can't believe how well it runs and wishes he had it done years ago. He says he cannot understand why they'd make a motherboard with bad capacitors. I told him I think it's all about saving money. He says the caps aren't that expensive and he can't see the company saving a lot. I said for one board, they're not bad, but when you're talking about tens of thousands of boards, it adds up.

Now though, I don't get technical with the customers. I tell them I found some problems, I tell them how much it'd be to fix. If they ask what's wrong, I'll try to keep it simple, like I found some failed components that need replacing. Once in a great while, someone will want the technical explanations. I found it's easier this way.

I'll do what you do from now on. If I see crappy caps, I'll replace them and just add more money to what they owe me.

Thanks!