2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

[Acesales]

Hello all, I'm back again with some questions. I have been able to get through a couple previous projects alone, thanks to you folks. I acquired a 55" Insignia NS-55D42NA16 LED TV, built 11-2015. No standby light, I get 168VDC across the filter caps and can chase it through the hot side till I get to the transformer SYEQ2612-T012A. A 4R7 4.7uH inductor snapped and sparked on the board without my help. I did not have any probes on the board at the time. It is LD1 and located between the AV5 RCA inputs. I can see no burnt or damaged areas. Subsequently, when viewing with a FLIR camera that inductor is "pulsing" every second or two and momentarily heats to about 105 deg F. Seems it is going into overcurrent protection? What should the voltage be on the secondary side of the Xfmr? Thanks

[budm]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Can we see the pictures of the whole back side of the TV showing how ALL the boards are connected together?

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

I removed the bottom speaker enclosure and found this. I have not removed the metal back- it appears the only wire going into the panel enclosure is the LED lighting cable. This is the newest and the lightest model I have worked on- compacted for sure.

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

I believe I found a schematic.

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Now this step down converter M3406-ADJ self destructed on it's own. Any ideas?

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

I believe this is the circuit for the burned step down converter.

[R_J]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

You could have a shorted component on the 1.15 volt line that caused the regulator to fail. It is likely that was the part that sparked originally and not the coil.

[budm]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

I would remove that burnt IC then check the RESISTANCE between GND and the output where the filter caps are, I.E. CD3~4, to see if it will show very very low resistance or not.

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Test to ground;
RUN= infinite
FB= 59 ohms
SW= 5.4K

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

The maximum allowable voltage in for the M3406 step down converter is 6.5V. I am measuring 12V after removing the burnt chip. Is it high because there is no load?

[budm]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

I expect the input pin to be fed from either 5VSTBY or switched 5V.
You may want to trace the input pin to see if it is connected to the 12V power source some how.

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Budm, I misidentified the circuit in question. The problem circuit is actually the 5V STB supply circuit. My schematic is wrong in regards to part ID's. So the MP1470GJ-Z actually burnt. I saw 5 pins, I wonder if the initial spark was a pin burning off.

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Pin 1 (GND) is supposed to be ground but I have an inifinite reading to several ground points.....chassis screws?
Pin 2 (SW) is shorted to ground. You guys were right.
Pin 3 (IN) 5.45K to ground and 0 volts.
Pin 4 (FB) trace is damaged.
Pin 5 (EN) shows 12VDC.
Pin 6 (BST) reads 59.5 ohms to ground.

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

More random unidentified circuits. The schematic I found for this TV is not great but the manual is for a Hisense, not Insignia, but very close.

[R_J]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Does pin 1 of the ic have continuity to the ground pin on that "pwr upgade" plug? it could be that the ground is isolated from the chassis

[budm]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

So with that IC removed and you check the empty pad of pin 2 and GND, does it show very low resistance still?
So the always on 12V is feeding this buck converter circuit to produce the always on 5VSTB.
If you do not see any shorted at the SW pad of that IC's then you may be able to use external 5V supply to feed that 5VSTB point and see if the TV will work normally or not, I would prefer to use power supply with DC current meter built in so you can see if the circuit is drawing excessive current or not, we also know that the IC is rated 2A so you know what the maximum the current draw by the circuit should be.
BTW, do you have the whole schematic or the whole service manual that you can upload for us?

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Here is the service manual I found. I couldn't read the part number on the burnt IC. I'm wondering if my PSU requires a different part number than what is listed in the schematic.

JR, there is no continuity to the "power upgrade" connector. I can chase pin 1 through a >1 ohm resistor and a capacitor.

budm, yes, shorted between pin 2 and ground, unless pin 2 is ground and I am chasing the wrong converter part number.

[budm]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Here is the service manual I found. I couldn't read the part number on the burnt IC. I'm wondering if my PSU requires a different part number than what is listed in the schematic.

JR, there is no continuity to the "power upgrade" connector. I can chase pin 1 through a >1 ohm resistor and a capacitor.

budm, yes, shorted between pin 2 and ground, unless pin 2 is ground and I am chasing the wrong converter part number.

If you follow pin 2, see if it is connected to an inductor or not.
Can you please provide straight shot of that section?
https://www.badcaps.net/forum/attach...7&d=1519095492

[Acesales]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

Here are the close ups.

[budm]

Re: 2015 Insignia NS-55D421NA16 No Standby-PSU Sparks

https://www.badcaps.net/forum/attach...4&d=1519428544
Pin 2 (to the right of the pin 1 that has triangle marking) looks to be connected to the 12V pin of the connector, can you check on that?