Re: lg 50pk550, my unfixable challenge!
oh and I replaced the 5 large capacitor on the z sub and the 5 on the x sub
veikra
Senior Member
Last Activity: 05-16-2020, 07:13 PM
Joined: 09-19-2012
Location: quebec, quebec
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lg 50pk550, my unfixable challenge!
Ok I've posted about this set before, but I want to diagnose it further. I found my harmony 880 remote that I almost threw in the bin many time so now if people can help me out I might be able to diagnose it better.
Heres the rundown.
Ive fixed the power supply more than a few time now, recap and the 3br chip.
Ive had the resistor blow on it 3 times. I have since most mosfet on that board.
Ive been able to make it work for a while, except when a very rapid change of screen. ie: getting killed in a game.
Lately a z buffer failed,... -
Re: samsung ln46a650 BN44-00203A psu part identification
yes, relay is working correctly. I doublechecked all the mesurements from the pads of all the parts removed this time. Saw some 150 Ohms, checked around saw the resistors and followed the traces to make sure. These mosfets cost me over 2$ each
Tv has been running for 2 hours now. It starts cold with 2 vertical line when cold, but clears out after a minute or 2. Im not gonna fix that, flex ribbon, bga. Not worth the time.
Keeping this one to myself, replacing a 40 inch samsung that's running a toshiba...Leave a comment:
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Re: samsung ln46a650 BN44-00203A psu part identification
FIXED!
So the NCT was shutting down all the low voltage and both QI816 QI815 shorted. Not replacing QI815 blew QI816 and RI868 ZDI805 RI866 and QI814.
The original failure was likely Q815 Q816 then the thermistor. Rest is my own fault but fuck it, ive got to release some blue smoke once in a while.
I used the 115ma mosfets 2n7002 since I couldnt get the other fast. Tv set is on test and I'll report how they do.Leave a comment:
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Re: samsung ln46a650 BN44-00203A psu part identification
It exploded and chunks of it flew off
yes the zener , the mosfet as well as the 4.7 resistor.
The schematics only says 2n7002. it's when I looked for a replacment that I found they were different amp rating with the same number...Last edited by veikra; 11-19-2017, 12:51 AM.Leave a comment:
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Re: samsung ln46a650 BN44-00203A psu part identification
yes, it is used to pull the gate of QI816 down.
Unfortunaly I don't know what kind of voltage comes out of the transformer to calculate the current.Leave a comment:
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Re: samsung ln46a650 BN44-00203A psu part identification
yes, I did mess up.
One question, the ST version of the 2N7002 is 200ma, the ON semi version is 115ma.
Do you think I can use the lower power On semi since the ST is backordered?Leave a comment:
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Re: samsung ln46a650 BN44-00203A psu part identification
I had no short after replacing Q816. It's when it turned on that I got the issue. probably both side of the half bridge were shorted, replacing one solved the short, but only until the new mosfet turned on.
I have 400VDC at the main filter caps with tv on.Leave a comment:
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Re: samsung ln46a650 BN44-00203A psu part identification
q816 and the ntc resurrected all low voltage. Tv runs but no backlight. Flashlight conclusive. Power on main 450V caps is low.
QI814 RI868 and ZDI805 blew up. What could cause this? They all sit around Q816. I dont think I missed seeing those when cleaning the board, but it is a possibility they already were.Last edited by veikra; 11-14-2017, 10:37 PM.Leave a comment:
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Re: samsung ln46a650 BN44-00203A psu part identification
Q816 was the short I was looking for. Diagram made is easyLeave a comment:
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Re: samsung ln46a650 BN44-00203A psu part identification
NTC is 13 mm of diameter.
The ferrites causes a short between + and - of the big 450V capacitors, so I know the problem is probably over that side of the circuit which they feed
Downloaded the pdf, going through itLeave a comment:
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samsung ln46a650 BN44-00203A psu part identification
I need help identifying these parts
The green resistor sit with one leg on either side of the relay power terminal. It blew up from a short circuit or current overload upstream.
The black inductors (deducted from symbol on board) I think they are the reasons for blowing fuses. These produce a .2ohm short between - and + of the big line capacitor if they are in circuit.
Might be a rabbit hole though! Need the green resistor to test... -
Re: LG plasma 50pk550 EAY60968801
sorted itself out after a few power cycle. Been booting up and working perfectly.
Whats the service menu button combo? I'd like to check the hours. It's very very nice, could be low hours.
tw2005: I owe you at least a few fosters for your help j/k, Ill get you some real beer!Leave a comment:
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Re: LG plasma 50pk550 EAY60968801
I replaced zd301 and it solved the rapid clicking.
Now I get the normal slow click and retry. click click red light dims slowly as it shut off both relays. The normal problem you know.
EXCEPT : I THINK this is mainboard related. Why? Because I can instantly start the tv if I probe the 5.1 rail at the mainboard connector relative to chassis ground.
I bet I could put a 10Meg resistor and it would work flawlessly
Something to think aboutLeave a comment:
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Re: LG plasma 50pk550 EAY60968801
Ordered new diodes, will post results tuesday or wednesday when I get themLeave a comment:
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Re: LG plasma 50pk550 EAY60968801
ZD301 seems shorted in circuit, Ill pull it and check whenever I get time tonight
Have the part number handy?Leave a comment:
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Re: LG plasma 50pk550 EAY60968801
im concentrating on the microchip. It's not getting feedback from the first relay clicking on. Did you download the schematics I linked?Leave a comment:
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Re: LG plasma 50pk550 EAY60968801
my this could be the optos ! I had some weird mesures with them but shrugged it off when remesured them correctly later... Definitely something Ill try and scavenge on other boards.
the 3 cycles then stop was my previous problem, and was a bad infineon 3br chip not booting right. I have bought many, and the first I replaced was a dud. Can't find them on digikey, only on shady ebay sellers.
I have a bunch of good working ones .Leave a comment:
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Re: LG plasma 50pk550 EAY60968801
microcontoller m81f4316 gets 5v, turns on relay rl101. That I know.
From my understanding, the relay sends power to the emiter of opto PC102 which activate the transistor side. So m81f4316 should get 4.5V on r03 (pins 28 ) when rl101 is activated.
Is that correct? Because I get nothing on that pin 0VLast edited by veikra; 09-28-2017, 02:19 PM.Leave a comment:
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Re: LG plasma 50pk550 EAY60968801
yes, I did go over it on all the major components. I dont have a microscope though!
What were your symptoms? I have Rl101 clicking on and off and no stable 5v standbyLast edited by veikra; 09-27-2017, 01:02 PM.Leave a comment:
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