NS-LCD32 - Power Cycling

[retiredcaps]

Re: NS-LCD32 - Power Cycling

I can't tell if this power supply uses PFC or not? If the large cap is around 450V then it might use PFC? If PFC is present, then the VDC across the large capacitor should be around 390V when the SMPS is working properly.

If the large filter cap is rated at 250V, then there is no PFC.

For the 1 second on/off, check all your diodes to see if any are shorted. It shouldn't take more than 10 minutes to test every diode on the board (including any on the heatsink).

[budm]

Re: NS-LCD32 - Power Cycling

It does have PFC, the inductor on the top left corner is the PFC inductor (it has BCK-100-02 on top). If you are only getting 350V, that is not right. You said you have replace that large cap, what did you replace with?

[retiredcaps]

Re: NS-LCD32 - Power Cycling

I can't tell if this power supply uses PFC or not?

After seeing budm's reply. I someone missed paragraph #2 in post 13 (as evidenced with my reply/quote in post #14).

Note to self . (I still haven't physically worked on anything with PFC).

[arunningpir8]

Re: NS-LCD32 - Power Cycling

I replaced it with the same cap from the new power supply board that was ordered. I checked it before putting it in and it checked out as perfectly in spec measured at 151uf. I had checked all the diodes on the board already and it seems they all checked out they have small resistance one way, large the other. I also checked the drop and they all had normal forward drops. There were however 3 or 4 diodes that had a reverse drop of 800 or so, which I still don't understand (2 each from the power supply board and the main board). I am assuming this is ok however as when I pulled one off the main board that had a reverse drop it didn't when taken out of circuit.

So does this mean there is a PFC problem? Does anybody still know why the power supply would keep 3.3v standby when hooked up to the mainboard but not when manually forced on? That's still my biggest question.

[budm]

Re: NS-LCD32 - Power Cycling

"I replaced it with the same cap from the new power supply board that was ordered." So you did not install the new power supply board in place to see if it works OK? Then you removed the cap from the new board to put into the broken board?

[arunningpir8]

Re: NS-LCD32 - Power Cycling

Well as per the first post the new board had the exact same symptoms as the old board, with the tv still cycling power on and off. It was the comment of new boards not always working that made me start looking into the power boards. I found the 2 issues with the old board and fixed them thinking maybe the new power supply was just sent broken, and rather than try and figure that out I found the common problem of the output cap being bad on the old power supply and thought maybe that was my problem. The only thing I didn't try with the new power supply before pulling parts from it was forcing it on by jumping PS_ON. Other than that, all the issues were identical between the 2 power supplies being plugged in.

[ben7]

Re: NS-LCD32 - Power Cycling

Well as per the first post the new board had the exact same symptoms as the old board, with the tv still cycling power on and off. It was the comment of new boards not always working that made me start looking into the power boards. I found the 2 issues with the old board and fixed them thinking maybe the new power supply was just sent broken, and rather than try and figure that out I found the common problem of the output cap being bad on the old power supply and thought maybe that was my problem. The only thing I didn't try with the new power supply before pulling parts from it was forcing it on by jumping PS_ON. Other than that, all the issues were identical between the 2 power supplies being plugged in.

Most likely the power supplies are good then, and you have a short circuit or other problem somewhere else on the unit.

[mu2]

Re: NS-LCD32 - Power Cycling

Hi,

Was this root cause of this problem ever found?
I have the same problem with the Insignia NS-lcd32. Power supply is marked 569HU222OD.
Was the A6159M ever replaced in the power supply? I'm suspecting it might be bad.

Mike