These seem to always kill themselves lol.

Okay, I have picture but no backlight. Sort of, backlight randomly comes on for about 30 seconds then shuts off. Right when I turn TV on BL does not come on. I waited and eventually boom backlight on. Then shut off, few minutes later, backlight on boom. Then backlight doesn't come on, but person said if you wait a bit BL and picture comes back and on.

I checked power board, voltages as follows
From PSU to main
PSON 3.4
Vamps 18v
13v 13v

All seem correct.

From PSU to LED driver...

Did you put the model number into the search [url]https://www.badcaps.net/search?q=qn75q70rafxza&searchJSON=%7B%22keywords%22%3A%22qn75q70rafxza%22%7D[/url]https://Did you put the model number...za%22%7D[/url]...

Set the tester to max voltage/amps. It has a safety on it. Set it to 330v or max.

I have a thread here that diagnosed a 75 like this model in America version, but as you can see the led driver is for 75/82 version. The led driver was bad in that TV but it gives good reference to a specific chip you can check that is supposed to have 3 volts. Maybe it's a lead to two bad led driver boards you have.

Look at post 56 picture that shows 3v on the multimeter and test those 5 points voltages with everything plugged in as normal and the TV on. Look at the picture and there is...

Re: qn75q70rafxza suiciding samsungs

I would love to know what was wrong on the old board.
Not sure if you buttoned up this TV yet but if not (and it were me) I would be probing and comparing to see where the fault was. An SMD or an IC.

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No, i post 2 time over here... but they were thought to another threat.... Lotas give me the attention so i delete them....

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Yes lol diah....

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lol.... wrong

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Diah, what are you talking about?...

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,,,,,,

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Okay I didn't get into all the exactness of it but installed new led driver board and it's working fine. Points 1 and 2 as established run at 3.1v as picture shows.

Thx story, lotas and diah and anyone I may of missed....

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sure you can take it out... but dont lost it..lol... after take it out u need to test to see the v you read before on which side in and if pin 1 ready to be 0v....

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So can I just pull pt9801 off the board then feed pin 1 the 3.3v? I don't know how to free it otherwise. And I will need to buy some resistors I see you say jump 3.3v with 1k all the time but I don't have one. Maybe scrap board. Okay will try tonight...

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did you read my post #56 ??
you need to free one leg of PT9801... to let Pin 1 zero V. and then we feed Pin 1 with 3.3V... i wrote an example... but you can use any source on TV like power on.... but in this case need to connect it via R 1K...

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Yup

Pin 1 shows continuity to both right and left side of pt9801 it shows no resistance continuity on right side on left side it shows 3 ohm resistance so almost continuity just low resistance. All 3 points show 1.408 v...

Re: qn75q70rafxza suiciding samsungs

1.408v you have also on pin 1 9802 ?

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Pt9801 has 3 ohms resistance so multi meter shows short because almost no resistance

There is 1.408 v coming in and 1.408v leaving...

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one things more.. if PT9801 (a PTC Thermistor as we thought ) and there swollen at the middle of the surface it will be in cutoff always.

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Will do lotas, will report back in about 4 hours

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You need to determine how and what is assembled on these three channels, what voltages they have at their terminals, and what transistors they are....

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or try by pass it with short circuit..

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Pt9801

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Bl doesn't come on at all anymore, not even 30 sec.

What would I try to freeze?

Lotas 2.4kohm 1 and 4...

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What is the general resistance between 1(3.3v) and 4(GND), is it not low?

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well every things possible... he can use cool spray to freeze it.... then turn on... if the 30 second BL on increase... if so will be funny case...

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Yes, anything can happen, and the designation on the board is “PT”....