Samsung SMPS BN44-00339A

[Loretto]

Hi all,
this unit comes from a samsumg LCD TV LE32C530F1W which stopped working after making a strong noise like something was exploded inside of it.
I opened it and found that fuse FP801S was blown, capacitor CP814 was completely disintegrated and MOSFET QP801S was shorted.
I replaced all of them and instead of the fuse I connected a 100 Watt bulb. Then, without connecting it to other TV boards, I switched it on, but the bulb begun to blink.
I thought that maybe the bulb was somehow interfering with the normal operation of the power supply, so I replaced it with a fuse, ... and boom !!! I burnt again the MOSFET QP801S I just replaced.
I had another one, so I replaced it again and did some more tests.

I checked all the electrolytic capacitors and noone seemed to be bulged or leaking: also the measure of the capacitance was good (don't know about ESR).
I checked the photocouplers and they seemed to be good, at least for the section of the infrared led: do not know about the phototransistor on the other side.

I found out that connecting PS_ON to cold ground, I had a stable 5 Volts on A5V (stand-by voltage) and the bulb stopped blinking.
In this situation, I measured the voltage on the legs of the main filter capacitor CP809 and I had a stable 324 Volts (our mains in Italy is 200 Volts).
But if I connected PS_ON to A5V, all the output voltages of the power supply became unstable and the voltage on the legs of CP809 was about 300 Volts, which was not good at all.

So I ordered a new ICP801 (FAN7530M) and a new ICM801 (FSFR1800US) and replaced both of them.

At the beginning, with PS_ON connected to A5V, everything seemed to be working: I even measured stable 13 Volts and 24 Volts and the voltage on the legs of CP809 reached about 415 Volts.
But then I begun to hear strange noises and didn't understand where they were coming from.
I rapidly switched everything off and noticed that CP809 (120 uF / 450 Volts) was warm and now seemed bulged, on both sides (top and bottom).

I replaced it temporarily with something similar (150 uF / 400 Volts) but the story is the same, if not worse: the bulb is steady on and all the output voltages are unstable.
Now, even the voltage on the legs of CP809 is fluctuating, from 100 to 300 Volts ... while, if I connect PS_ON to cold ground, everything works like before.

I replaced resistor RP822: nothing changed.

I measured CM801S without disconnecting it from the board and it seems good.

Resistor RM803 seems good too: anyway, when PS_ON is connected to A5V, as soon as I plug the power supply, the voltage across it is e few millivolts (less then 10) and then goes to 0. Is it normal ?

I really don't know what else to do: I played all my cards. Any suggestion ?

Thanks.

[EazyBone]

Pictures of board I don't download pdfs because of security

Here's a link to a repair kit. I would check these items

https://www.ebay.com/itm/27683646718...mis&media=COPY



https://www.ebay.com/itm/31654714827...mis&media=COPY

Also $14 with coupon. At this price I'd just buy the board.

But potentially those items in the repair kit are bad, looks like you have replaced a couple of them

[Loretto]

Yes, I replaced all of them except for the diode which should be DP804 (but I checked it and should be ok) and the DIP IC (ICB801, ICE3BR1765J), which is responsible for the standby voltage (which is ok, in my opinion).

Thank you for your response.

[Loretto]

By the way, thanks for te links. As for the replacement board, unfortunately that customer does not sent it to my country. And here in Italy I can find it, but the price is not less than 30€, shipping charges included.

Anyway, now it's a matter of principle: I would like to find the faulty component, at least in order to learn something more.

If you need any board pictures, I can take some and upload them here ...

[EazyBone]

I don't blame ya, as a matter of principle and all the effort in. I'm not sure. I know there is a power supply section in here also. May be useful to post there too? I can only provide basic info I'm not advanced enough