[Solved] Samsung UE40D5000 - Overheating Issue in BN44-00473B Power Supply Module after PFC Failure Repair

Hello, the receiver had a blown mains fuse and a punctured key in the PFC system in the power supply module BN44-00473B . In the vicinity of this key (QP801s) a dark brown plate - symptoms of prolonged high temperature of the key. I replaced the key with a new one, although I used an IGBT transistor with parameters corresponding and current exceeding the original K12A60D.
I started the power supply "through" a 100W bulb, i.e. only in standby there was no short circuit (I did not know then that PFC in this model starts with the main converter)
When starting the TV set it turned on and it came for 3 minutes, the key warmed up and got a short circuit again.
Now I replaced the key with a 2sk3797 mosfet with very similar parameters to the original and the FA5591 driver. After this exchange, the receiver works, but the key heats up a lot. I'm afraid to leave the receiver for a long time - I suppose the key will break again. Maybe some of you have worked on the topic and will help. I found a diagram of a similar BN44-00358 power supply on the same controller, but here two such keys are used in parallel and they are controlled directly from the controller in my power supply, control is via a buffer of 2 NPN + PNP transistors connected in push-pull.

Thanks in advance
Michael

https://elektrotanya.com/samsung_bn44-00473b_smps_sch.pdf/download.html

Thanks for the response, but although the marking of the power supply is the same, it is not this diagram.
best regards
Michael

https://www.electronica-pt.com/esquema/lcd/bn44-00473a-ue40d5003-29726/

Thank you for the diagram from the first drawing in pdf really similar elements differ in value, but almost the same can come up with something. Maybe the system wakes up somehow. If I control the key incorrectly, I have to "harness" the oscilloscope to make some measurements. For now, I carefully follow how it works so as not to let anything go, I was able to turn it on with the artificial load of the 5V and 13V branches in the form of light bulbs.

Thank you, maybe someone else will say something in the subject.

Regards, Michał

Added after 1 [hours] 17 [minutes]:

I made measurements at the output of the chip from PFC (FA5591), it turned out that for a moment after plugging the plug into the socket there is a nice square wave with an amplitude of about 10V and as soon as the converter starts, the main waveform increases its frequency and turns into pins with slight oscillations with amplitude ok 20V. He certainly does not stand it well and the key becomes very warm after a while, and the power supply works practically without load. Instead of a fuse, a 220V / 100W light bulb is turned on to protect the key from damage.
I made oscilloscope measurements: the PFC key control output directly from the IC these higher pins and waveforms on the gate after the buffer and matching elements (the waveforms could not be better synchronized) Y gain 5V / d time base 1us


best regards
Michael

Hello. The same poverty happened to me, tomorrow I'm going to get the transistor. I searched the forums, and found the problem of overheating of this transistor (MDF11N60), it turns out that the problem is the LP801S transformer, he wrote that the conversion helped. This has to be checked. best regards

About FA5591 also written on this forum, e.g. Link
Link

as the field fell> to replace (without measuring) elements in the gate, field, capacitors on the connector. Field DS, FA5591 and improved soldering of "high-ohm" resistors in pin 1 (FB) / * it is worth measuring them (after coming out of the board)

Helpful e.g. SM under BN44-00422B
* ICP801 (code 5591) FA5591

Thanks for the answer, I was hoping it would work out, I do not have the IC (2 weeks to order it), so I took the risk and put almost the original MDF11N65, after turning it on the fuse shot after 5 seconds, I gave 3.15A. I checked the elements in the area where there were suspicions of cold solder and corrected, I found nothing else that was damaged. You can see this overheated place, almost black under the heat sink.
The transistor blew into two halves ha haha. OKAY. I order parts and one more approach.

Hello, you made a basic mistake, you did not give a 220V / 100W bulb instead of a fuse. It helps when starting the inverters; the principle is simple: a light bulb, not a key
You run the power supply "on the table" with a dummy load in the form of light bulbs, one "flashlight", the other "Christmas tree" for the appropriate voltage of 5V and 13V. This way you will avoid losses.

best regards
Michael

Thanks yes i know you already talked about what a loss ?? one transistor ?? i think in this case this is a risk talked about sooner why not take a chance? Or maybe my case is different?

Then order ten keys at once, you will save on shipping

You're right why I didn't think about it.

Added after 5 [minutes]:

I really appreciate humor, professionalism and good advice.

I improved working conditions.