Insignia NS-40DR420NA16 no power

[Daveleone]

All --

I have an Insignia NS-40DR420NA16 40" LED TV with no power (no lights even on the logo).
I checked the fuse on the power supply and at least I have 120V across the fuse. But on the cold side I have 0V at the PS_ON pin, and ~0.04V at the 12V pin, and ~0.02V at the 3.3V pin. 0V between the LED+ and LED- pins as well. So, I figured "bad power supply".
I bought a replacement power supply off of eBay that said it was a "brand new" pull from a set damaged during shipping. Well, the new power supply has the same exact voltage readings.

What am I doing wrong? Could I have gotten another bad power supply? Or what should I check next? Your help is greatly appreciated!

Thanks,
--Dave

[dskall]

Re: Insignia NS-40DR420NA16 no power

How are you taking your measurements? If you read across your fuse then you have bad fuse.

[Daveleone]

Re: Insignia NS-40DR420NA16 no power

Sorry for the poor wording above. I actually measured between each side of the fuse and the Neutral line on the power plug. Both readings were 120v.
I also tested for continuity across the fuse with it unplugged and it had continuity.

[dskall]

Re: Insignia NS-40DR420NA16 no power

What is dc voltage across the main cap. Big one in middle of board?

[Daveleone]

Re: Insignia NS-40DR420NA16 no power

171 volts DC

[dskall]

Re: Insignia NS-40DR420NA16 no power

You have two bad power supply if you have no standby voltage and you took measurements with black probe on a cold ground and dcv.

[dick_barton]

Re: Insignia NS-40DR420NA16 no power

All --
But on the cold side I have 0V at the PS_ON pin, and ~0.04V at the 12V pin, and ~0.02V at the 3.3V pin. 0V between the LED+ and LED- pins as well. So, I figured "bad power supply".
--Dave

You are taking those measurements at the output with your meter set to DC volts?

[Daveleone]

Re: Insignia NS-40DR420NA16 no power

You have two bad power supply if you have no standby voltage and you took measurements with black probe on a cold ground and dcv.

Let me clarify, since I'm really new to this and don't really have a clue what I'm doing

The DC voltage *across* the main cap is 171v (if I measure between the left and right wires of the cap). If I measure either of the wires as compared to ground it's 0V. Not sure which measurement I was *supposed* to do.

You are taking those measurements at the output with your meter set to DC volts?

Yes, all of the original measurements (PS_ON, 12v, 3.3v, LED+, LED-) were taking with DCv between the pin and ground.

[dskall]

Re: Insignia NS-40DR420NA16 no power

Seems odd to have two with exact problem. Then again same boards will share same weakness. Based on your readings plugged in all smps should have a standby voltage. If you don't the power supply is bad.

[budm]

Re: Insignia NS-40DR420NA16 no power

https://www.badcaps.net/forum/attach...4&d=1492990844
This power supply board is an always on power supply with only one main power transformer T200. The SMPS IC should be on that black heatsink.
We need good clear straight shot pictures of the bottom side of the power supply board to do circuit tracing. There may be fusible resistor for feeding B+ to the SMPS IC.
So you are really sure that there is no DCV on the connector CON2 at all, right?

[Daveleone]

Re: Insignia NS-40DR420NA16 no power

So you are really sure that there is no DCV on the connector CON2 at all, right?

Ok, I put my original power supply back in, which seems to (maybe) be in slightly better condition than the replacement I bought. All of the readings are the same, with the exception that 3.3v on CON2 reads between 2v-3.3vDC fluctuating. And 12v reads 0.34vDC (so 12v is still bad). LED+/- still read 0, PS_ON still reads 0, big cap still shows ~170v across the pins.

I'm excited to work on tracing down the issue with you guys Pic of the bottom side attached.

[budm]

Re: Insignia NS-40DR420NA16 no power

At least the original board is doing some thing. At this point it looks like the power supply may be in shutdown/restart mode which can be due to bad startup/running cap, bad filter caps in the cold side, bad rectifier diodes in the cold side, the main board is drawing too much current. So those parts need to be tested. I hope you can get money back on the replacement board.
You you remove connector CON2, will the 3.3V become stable?

[Daveleone]

Re: Insignia NS-40DR420NA16 no power

Ah I should've said - all of these readings are with the both the led and con2 cables disconnected. If needed I can test with the cables connected when I get home from work tonight.

[Daveleone]

Re: Insignia NS-40DR420NA16 no power

With CON2 (Main board) and CON3 (LED) connected:

Big cap reads 168v, CON2 3.3v fluctuates between 0v-1.5v, 12v fluctuates between 2.2v-2.6v, and PS_ON fluctuates between 0v-1.5v (just like the 3.3v signal). CON3 LED+/- are both still 0v

[budm]

Re: Insignia NS-40DR420NA16 no power

So test what I suggested in post 12.

[Daveleone]

Re: Insignia NS-40DR420NA16 no power

So, the seller sent me a replacement power supply. The TV still doesn't power up, and still no LED indicator on the Insignia logo.

With the main board DISconnected, I get 2v-3.38v (fluctuating) on the 3.3v pin of the power supply. 0v on the PS_ON and 12v pins.
With the main board connected I get 0v-2.2v (fluctuating) on both the 3.3v pin and PS_ON pins of the power supply. And 2.8-3.8v on the 12v pins.

Questions:
1) Is it possible that I have a 3rd bad power supply? Seems less likely at this point.
2) Is the PS_ON pin driven by the main board? (in other words, is 3.3v initially fed to the main board and then the main board powers up and feeds a PS_ON signal back to the power supply to power up the 12v circuit?)
3) Is it possible that the power supply is working and the main board is not feeding it the proper PS_ON signal, or *is* but shuts down as the 12v circuit comes online due to some other issue?

Thanks again for the help.

[budm]

Re: Insignia NS-40DR420NA16 no power

The 3.3V standby power supply should not be fluctuating period, especially without any load connected.
The PS-ON comes from main board to turn on the rest of the power supply.

[dskall]

Re: Insignia NS-40DR420NA16 no power

Maybe check your power supply cord. Is 120vac going in steady?

[Daveleone]

Re: Insignia NS-40DR420NA16 no power

The 3.3V standby power supply should not be fluctuating period, especially without any load connected.
The PS-ON comes from main board to turn on the rest of the power supply.

Do you know what the PS_ON voltage should be? I have a voltage generator. Maybe I could try to power up the power supply without the main board connected to see what happens?
If not, please help walk me through testing the things you mentioned in post #12. As I mentioned, I'm very new to this so I will need some hand holding. If you could point me to the right components in the picture and explain how I should test them I'd appreciate it very much. Thanks!

Maybe check your power supply cord. Is 120vac going in steady?

Good idea. I checked that and it is solid. I even tried a different power cord and still no change.

[budm]

Re: Insignia NS-40DR420NA16 no power

Do you know what the PS_ON voltage should be? I have a voltage generator. Maybe I could try to power up the power supply without the main board connected to see what happens?
If not, please help walk me through testing the things you mentioned in post #12. As I mentioned, I'm very new to this so I will need some hand holding. If you could point me to the right components in the picture and explain how I should test them I'd appreciate it very much. Thanks!



Good idea. I checked that and it is solid. I even tried a different power cord and still no change.

No need to waste time simulating the PS-ON signal until the standby Voltage is corrected first.