Dead Insignia 42" NS-L42Q-10A

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

I have to go to bed. It's real close to 3AM here and my wife gets a little upset if I stay up all night playing with stuff like this. Thank you again for helping me Budm. I really appreciate it.

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

My U706 says on it:
194B
0935
Z402

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

So I was thinking perhaps my U706 chip is bad. When I check each pin against ground, almost all of them measure close to 0 ohm resistance. I ordered a new U706 chip from digikey. However, I don't think my current soldering station can solder such a small chip. I went a head and ordered a Weller WHA900 hot air rework station and a 2.5 MM round nozzle for it. I've been watching some videos on line, and I don't think I'll have any trouble removing the chip. For replacing it though, what's the best solution? I was thinking of ordering some soldering paste. From watching this video: https://www.youtube.com/watch?v=f_yFDpSTfao It looks like they just cover the pads on the board, put the chip over it and then use hot air. Even if I have the paste covering the pads and the spaces between the pads, it looks like when heat is added, it'll actually move to the pads and the components. Does this sound like a good method? Also, is there any way to be certain that buck regulator (U706) is bad? Thanks.

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

So I've had some time to think about this and I got my hot air rework station not too long ago. I don't think it's the U706 chip. The reason I think that is because if it was, pin 2 of u702 wouldn't be reading close to 0 ohm as well. Am I right in thinking that? U505 could be bad though. It's next to the HDMI cables. My sister said the 360 was plugged into an HDMI port when the TV and the 360 broke. I'm thinking of removing U505 and seeing if I still read 0 ohm on U702's pin 2. What do you guys think?

[budm]

Re: Dead Insignia 42" NS-L42Q-10A

You just have to start removing parts and see at this point.

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

Thanks. I have one last question. I pulled a cap a while back, it's a 10v 220UF electrolytic capacitor. It's made by Elite and it's the EG series. I tested it with my ESR meter and it has an ESR rating of 0.60 ohm and a capacitance of 201.5uf. The capacitance is within the +-20% range but how do I know what the ESR value should be? I've attached the data sheet and I can't find anything in it that shows what the ESR value is supposed to be. I have a chart that came with my ESR meter that gives me rough values but according to the parts list on this Insignia, it's a low ESR cap.

[budm]

Re: Dead Insignia 42" NS-L42Q-10A

It is shown as Impedance (0.400 Ohms) instead of just ESR.

Reading 200uF instead of 220uf I would replace it, most lytics cap will usually show higer capacitance on the higher side.

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

Oh, thank you. Also, I removed that chip, U505 with my Weller....now I test the pads where that voltage regulator was (U702) and I'm getting readings that aren't 0 ohm. The fat pad is reading 0.920 Kohm right now, the other pad that isn't ground starts at like 2 Kohm resistance and reads up. When I remove the probe, put it back on, it's in the Mega Ohm place. Does that mean the chip I removed is the culprite?

[budm]

Re: Dead Insignia 42" NS-L42Q-10A

OK, please remind me what the U505 is? So the sections that show <1 Ohm in the earlier posts now no longer show <1 Ohm?
I am losing track on this thread.

OK. I see this post:
https://www.badcaps.net/forum/showpo...1&postcount=19
That is a big IC U505 is part of the HDMI. The TV may work now with that IC removed. HDMI IC failure is usually due to power surge or lighting close by that will damage the cable box and the HDMI circuits.
So if the low resistance went away, then it looks like you found the cause of the problem.

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

Yes. The sections that showed <1 Ohm in the earlier posts now no longer show <1 Ohm. U505 is an 80 pin HDMI switching (?) IC. SiI9185ACTU is the chip number. It's made by Silicon Images.

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

Sorry, I thought the bottom part of your post was your signature. Just read what you wrote. So with that chip removed, I can try to turn on the TV and see if it works? I ordered a new HDMI switch IC from China or Hong Kong. It might take a while to get here. Thanks for the help. I'm going to go to bed now, I'll try it out in the morning, if you think it's safe.

[budm]

Re: Dead Insignia 42" NS-L42Q-10A

It will be safe to power up the set, just be sure you do not have any solder bridge on those small pads that you removed the IC.

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

I'm gonna use my desoldering braid and go over the pads. I normally do that when I remove a chip. It does look like there's some bridges. I'll let you know if the TV works when I'm done.

[budm]

Re: Dead Insignia 42" NS-L42Q-10A

I also clean off the flux with Acetone so I can easily see the pads and traces.

[Spork Schivago]

Re: Dead Insignia 42" NS-L42Q-10A

I did the same. I need some new desoldering braid or a new iron. I'm using radio shack desoldering braid and a radio shack digital soldering iron. With that iron and the braid, I always have trouble removing soldering. I think it might be the soldering station because when I try to back out caps, I can't even melt the solder 9 out of 10 times. Some of these caps came right out, some didn't. I was thinking for braid, I'd buy some of that chem-wik stuff and maybe for an iron, when I get some cash saved up, perhaps a Weller, although I've always like the JBC brand.

I put the board back on the TV, soldered that voltage regulator that I had to replace with the new one that came in the mail the other day and as soon as I plugged in the TV, the red light came on. We hit the power button, a blue light came on, the back lights kicked on and it said HDMI 2. Screen was blank (black but backlit). I believe we found the problem. I bet that Hitachi that had a similiar board as mine and had almost the exact same problem has the same chip bad, that HDMI switch chip.

Once I get the new chip, I'll solder it on using my paste and I'll let you know if it works. Thanks for the help Budm.

[HAHOMETP]

Re: Dead Insignia 42" NS-L42Q-10A

Folks,

I hope Spork Schivago does not object that I decided to continue his thread rather than start my own because my symptoms are almost exactly like the ones described in the OP with a few exceptions. I feel the symptoms are related and it would be beneficial for the archives to keep this within the same topic.

My Insignia died after the recent lightning storm that took out yet another TV in the household. In that other TV the HDMI chip on the motherboard has literally burnt down to the Si substrate. I suspect that this Insignia was also damaged via its HDMI port. However there is no visible damage on either PCB in this TV.

The voltages in my Insignia are the same whether I press the power button or not:

CN903
SILKSCREEN VOLTAGE
ON/OFF 0v
PDIM 0v
+12V 12.6v
+12V 12.6v
Gnd
Gnd
Gnd
24V 24.6v
24V 24.6v
PS_ON 4.0v
5V 5.0v
5V 5.0v

Both large capacitors C929 and C930 show +290v to ground.

Of the three voltage regulators (U709, U708, U703 and U702) on my motherboard it's the U703 whose output (Pin2) is shorted to ground. That's with Pin1 and Pin3 desoldered and lifted off the PCB per budm's recommendation on the first page.

Using the schematic diagram provided by Spork Schivago in the OP (thank you very much!) and budm's excellent pointers I quickly determined that the 3.3v bus D3V3 was shorted to ground. Then I got stuck.

The 3.3v bus D3V3 must be shorted throughout the whole motherboard, right? In reality some points do indeed show 0 to ground whereas some show 1.16k. My findings are below:


U702 Pin2 0
U207 Pin5 0
U209 Pin5 0
U404 Pin2 0
U405 Pin8 0
CN401 Pin13 0
R407+R408 0

but

U511 Pin2 1.16k
U505 Pin23 1.16k
......................Pin43 1.16k
......................Pin55 1.16k
......................Pin63 1.16k
R528+R529 1.16k



In order to isolate the short in the D3V3 bus I desoldered a few semiconductors. Here are the results:

Desoldered U207, Pin5 - D3V3 still shorted to ground.
Desoldered U209, Pin5 - D3V3 still shorted to ground.
Desoldered U404, Pin2 - D3V3 still shorted to ground.
Desoldered U405, Pin8 - D3V3 still shorted to ground.
Desoldered U505, Pin23 - D3V3 still shorted to ground.
.........................Pin43 - D3V3 still shorted to ground.
.........................Pin55 - D3V3 still shorted to ground.
.........................Pin63 - D3V3 still shorted to ground.
Desoldered U511, Pin2 - D3V3 still shorted to ground.

The only chip that I did not desolder is the big BGA IC U401. In page 77 of the Service Manual from the OP you can see a bunch of U401 pins connected to the D3V3 bus. I have no idea how to disconnect those in order to test the bus as to eliminate the U401 from the suspects.

Questions.

1. How is this possible that the very same bus D3V3 sometimes shows 0 ohms yet sometimes shows 1.16k depending on where I am testing it on the PCB?

2. How can I cut the U401 off the D3V3 bus in order to test the latter?

3. It appears that the OP had gotten rid of the short in the the U702 regulator (1V8_STB bus) by removing the HDMI processor U505. I disconnected the 4 relevant legs in mine and it didn't eliminate the short in the S3V3. Do you feel that if I remove the U505 anyway I might get rid of this short?

4. The same goes for the U511 HDMI chip.

5. Why is PS_ON showing 4v while the TV is OFF and the LED is red?

I hope I haven't bored you to death, folks.

The picture of the motherboard (not mine, but identical to mine) is attached.

[HAHOMETP]

Re: Dead Insignia 42" NS-L42Q-10A

A follow up for the archives. Bought a working motherboard off ebay and the TV is alive again.