Re: Samsung UN50H6350AFXZA 1/2 Panel Failure?
Makes you wonder what the average life of a UHDTV panel is going to be, seeing that 1080p panels die rather too frequently. Pushing technology beyond it's current limits i think - "yeah, it will work, but we can't guarantee it will still be working in a years time".
Steve.B
Senior Member
Last Activity: 12-22-2022, 04:59 PM
Joined: 12-21-2008
Location: North Devon
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Re: Samsung UE46D6530 no picture/sound
All this talk of bad panels in the D series is not good to hear, seeing that i invested in D6100 a couple of years ago. Is there a pattern emerging showing which make of panels are failing? (I assume samsung are using various manufacturers for the D series panels?).Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Both of the smd fets were bad, one was o/c, the other had a constant resistance of 57ohm between gate and source.
Not sure about that driver chip, did not know how to test it, and did not want to start probing the new one i bought for comparison to the old one in case i damaged it. The new driver chip only cost a couple of quid, so i decided to swap it, just in case it was bad. And seeing that there were so many components in that circuit that had failed, i think it was likely the chip also had a fault....Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Success!!!
The last of the parts arrived today - the little SO-8 mosfet driver chip, and two of the tiny SOT-323 2sk3018 mosfets. I fitted them, along with the 5 replacement resistors, plus i also replaced the main power mosfet (Q406), this time i put a RJK5010 back in, rather than the uprated RJK5020 i put in last time.
I felt great relief and satisfaction when i pushed the power button and was welcomed with a flashing green light, then she booted up like normal. I even had an added bonus, the thin vertical...Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Well, i will wait for all the parts to arrive, then i will know for sure if i have found everything. If it's still not working after all of this, then a new board it will be.
I am thinking about using budm's trick of wiring it up to the mains via a couple of light bulbs when i first put power to it, hopefully that will stop it having another meltdown if there is still a fault.
Seeing that when i first checked the mosfet driver circuit it seemed fine, no blown resistors or shorts, i can only think that when the...Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Q422, looks like the drain from that Mosfet supplies the Vcc for IC406? I am guessing that the Vcc is very important for IC406, so a faulty Q422 would cause a major issue.
I think i might replace IC406, not sure how to test it, but seeing that i now have 5 different faulty components that connect to it, i think changing it would be a wise move.
Yes, it would have been easier to just swap the whole board, but this is so much more interesting, and rather fun. Shame my living room now looks like a workshop though....Leave a comment:
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Re: MOSFET 2SK3018 advice
Thank you budm, i have ordered a couple of replacements, luckily they are easily available. I ordered a couple in case of mishaps when fitting - never fitted one of those tiny SOT-323's before.Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
A further bit of information. It looks like i have found another blown fet on the board. Q422 is showing a constant resistance of 57ohm between the gate and source pins. I have received advice elsewhere on the forum that suggests that the fet is damaged. Again i am lucky that it is a commonly available part. I have ordered a couple of them, just in case i mess up fitting it the first time around. It a tiny SOT-323 device, could be fun fitting that!
So this is my current list of known bad components:
R448...Leave a comment:
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Re: MOSFET 2SK3018 advice
Thank you for the replies.
Yes to both of them, whichever way round i have the probes, i still get a 57ohm resistance. I also took your advice and removed the mosfet from the board (though i was certain there was not a path between them on the board). With the part removed from the board, i still get the 57ohm between Gate and Source.
So this fet is no good? Thank you again for the information, i feel i am making progress with the trouble shooting now.Leave a comment:
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MOSFET 2SK3018 advice
I am hoping someone will be able to advise me on this mosfet. I am trouble shooting a circuit on a Panasonic plasma psu - thread [URL="https://www.badcaps.net/forum/showthread.php?t=32591"]here[/URL], and have noticed that i have a constant resistance of about 57ohm between the Gate and Source pins on this little fet, (Q422). I have followed the traces on both the pcb and the schematic, and have determined that the resistance is within the fet itself.
Here is a link to the data sheet for the Mosfet, it's the SOT-323 package.
[URL="http://www.sztuofeng.com/pdf/2SK3018.pdf"]http://www.sztuofeng.com/pdf/2SK3018.pdf[/URL]... -
Re: Panasonic TH-42PX70B Blowing mains fuse.
I can answer that one for myself, D415 is a Schottky Diode - D1NS4. Just looked at it's data sheet and the low voltage drop i am getting is normal for this type of diode....Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Thanks, so pin 6 is getting what it needs, that is the main thing.
I am double checking everything at the moment, D415, i have taken it out of circuit to check it properly, using the diode check range on my meter, i am only getting a reading one way, like i would expect, but the reading is rather low to what i normally see with a diode, i am getting around the .205 mark. Would that be just down to the type and value of the diode? Or is it something to look at do you think?...Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
No, they are not removed from the board yet, but seeing that they are totally open circuit, i don't think removing them will change any readings, but i will pull them out now, just to make sure.
With regards to the bridge rectifier, yes, pin 6 of the IC does have continuity to one of the rectifier pins, the one that connects at ZH17. Will that be the GND reference i am looking for with regards to the IC? But again, that connection does not have continuity to any of the chassis GND points....Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Ok, i have continuity between pin 6 of the IC to the pad that connects to R448, 449. But i do not have any continuity between the resistor pads (either side of resistors) and chassis gnd points.
I seem to remember reading in other threads about different gnd points. Would there be a difference between the DC and AC ground points? If so, would the GND point for that IC be a DC GND point, rather than an AC ground point? (I am presuming that chassis ground would be on the AC side of things? Am i making any...Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
IC406 seems to be a standard L6561D, could not find it in the parts list, but the schematic gives that number, and that matches what i can see on the actual chip. Plenty on eBay, so no problem getting hold of one. £2.46 with free postage. - [URL="http://www.ebay.co.uk/itm/Stmicroelectronics-Pfc-90Ua-Start-Disable-Smd-6561-L6561D-/121112501175?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c32de1bb7"]http://www.ebay.co.uk/itm/Stmicroelectronics-Pfc-90Ua-Start-Disable-Smd-6561-L6561D-/121112501175?pt=UK_BOI_Electrical_Components_Supplies_ET&hash=item1c32de1bb7[/URL]...Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Thanks, Tom, I will go with the 0.22ohm for now, at least until i know that we have life again....Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Thank you both. So fitting the 0.22ohm ones i have found could cause problems. But i am wondering if they would be good enough just to determine whether this thing is going to go into meltdown again once i have replaced the known faulty parts? Once i know that is not going to happen, then i would not mind waiting a few weeks for the correct value to arrive from the far east. I have searched a lot of places in the UK, and 0.22 is the closest i have found. I have indeed even tried looking for them in an axial package, but no luck there...Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Thanks very much for explaining that, i knew i had to have something mixed up. Very glad you mentioned it because i could have made a bad mistake there.
I am guessing they use 'R' for clarity, less chance of an R being missed. (Unless your not sure to start with like me.
But i am still wondering how critical the value is, i am still struggling to find replacements at that value, closest so far is 5w 0.22ohm. Not understanding how these resistors are being used, i would not like to guess how critical...Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Have started looking through the schematic for the P board, have come across something that's really confused me.
You will remember that earlier i had noticed that both R448 and R449 were both o/c, they are the 5w ceramic cement ones. this is what is written on the actual resistors...
5w 0.12ohm
According to the schematic, they should be either 10r for the AB / AD / AG / versions of the board, or 12r for my AE version of the board.
So am i interpreting the numbers...Leave a comment:
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Re: Panasonic TH-42PX70B Blowing mains fuse.
Just to clarify.
Before i fitted the new main mosfet i checked R493 and R439, they checked out good. I also checked D415 and R406, they were good. And Q404 was not showing any shorts, so i assumed it was ok.
But after fitting the new mosfet and trying to power up the set, i found that R493 and R439 had gone bad, one completely open circuit, the other had nearly doubled it's resistance value.
So like you, i am also a bit confused, i know the insulator was in place because it's stuck...Leave a comment:
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