qn75q70rafxza suiciding samsungs

[Diah]

Re: qn75q70rafxza suiciding samsungs

13v comes to the board, in order to power the controller there must be a dc/dc converter whose output should be 3.3v.
There is also a controller on the motherboard and they communicate with each other and give commands to each other.

you drive him in wrong direction...
BL on for 30 second only mean there are SOS come to MB to turn off BL
this SOS are Firmware.... also it could be main parts like Panel. or BL..., resetting 1 option, & force panel & BL to turn on Option 2

No Micom Option like in LG at Samsung. no program... its just native Linux. glitch easy happen when sector on nand / SPI dead

[lotas]

Re: qn75q70rafxza suiciding samsungs

Well, let him clean off the sealant from micom and read what kind of chip it is, most likely it's Renesas, st32, pic, where its own firmware is located.
And this is the bus through which communication takes place between them.

[EazyBone]

Re: qn75q70rafxza suiciding samsungs

@ sony, just saw that. Yes I'm trying to confirm that it is that driver board though. Still haven't done what diah said to do yet, gonna work on it in a couple hours, start with diah suggests and move down the list here checking. I probably wouldn't be able to fix it, so far can only fix power boards so I'd look to buying it, but need to make sure it ain't actually main board sending problem either. Thanks will get more data tonight.

This group is great lol. The game of tv fixin

Edit, I saw rest of posts now.

The BL has come on twice now randomly for 30 seconds and never again. I turned on TV for first time, took 5 min for bl to come in, on 30 sec then off for couple min, then on one more time 30 sec and off again. Hasn't come back on since.

[EazyBone]

Re: qn75q70rafxza suiciding samsungs

Diah do you mean reset from service menu, or from settings/general/reset. The setting method will NOT stop greying out reset. I've closed everything and googled every method to reset, It will not ungray.

I accessed a service menu while TV was on by doing mute, up down select mute, I can't find how to reset it from there.

Is that the menu you are talking about? Or is there some way to bypass that grey out, I've tried everything lol driving me nuts.

[Storyteller12]

Re: qn75q70rafxza suiciding samsungs

@ diah, I have turned down the backlight which was pretty low to begin no change

As a note I disconnected the PSU to LED driver and the fault pin reads 4.5v at plug in. I reconnect the PSU to LED driver and then it reads .058 to 0 and goes back and forth. Is fault similar to BL ERR on Sony?

@story, any combination of disconnect ribbons and clips all combos tried BL doesn't turn on.

@anyone, does anyone know if the LEDs are blue on this TV?

Anyone know how I can test the LEDs with a LED tester?

Edit, I have found how to test them I believe using ribbons. Will put results

Yes, leds are blue on this tv. It's a QLED

[Storyteller12]

Re: qn75q70rafxza suiciding samsungs

Sounds like led driver board is bad if the backlights all tested working with same voltage on tester and psu voltages all test good without anything attached

[EazyBone]

Re: qn75q70rafxza suiciding samsungs

Sounds like led driver board is bad if the backlights all tested working with same voltage on tester and psu voltages all test good without anything attached

Yea all LEDs tested 131v with around 83ma through tester. All 56 different test points lit up.

Like I said fault from PSU is at .060 when connected to LED driver and disc it's 4.7v I'm not sure if that means anything as I can't find data on it. Also that test points on LED driver reads 1.4 not 3.3 as it says. Still going through all steps people told me, can't reset it yet.

Will keep messing around here

@diah factory reset done I figured it out. No change, I'm still trying to find out what 2 things you are asking me to connect as I don't know what you are talking about. I'm taking a closer picture

In picture I have circled. Are you saying plug TV in onto standby and just stick a jumper on those two points and hold them there? Or turn TV on and then jumper them? Not gonna do anything until confirm. Also both those test points show 3.3v

The full picture and sound works still, so are we testing panel? Cause everything looks perfect on panel. Thanks

@ lotas here is a picture without scraping anything off, should be readable. So far I have tested many points on the board and cannot find 3.3v anywhere on it. I find many 1.4v around that chip just like the test points 1 and I found 2.6 at a gate. So I see no signs of 3.3 anywhere on driver board

[EazyBone]

Re: qn75q70rafxza suiciding samsungs

@ lotas so here is what I get from main board to LED driver when disconnected. All test coming @main

15 0
13 .110
11.220
9 0
7 3.3
5 5.1
3 0
1 0

16 .004
14 .002
12 1.67
10.006
8.002
6 .002
4 3.3
2 .006

Compared to when plugged into LED driver

16 .015. 15 0
14 0. 13 .142
12 1.32. 11 .169
10 .006. 9 1.407
8 0. 7 2.76
6 1.407. 5 3.2
4 2.76. 3 0
2 .045. 1 0

So I see an absence of 3.3v all over the LED driver but it seems MB is sending 3.3v in 2 different places. Also lotas, the chip you pointed out only showed the 1.4v as I stated at that test point there was no 3.3v on it at all.

So as storyteller seems to infer and lotas I think maybe LED driver has gone bad. Gonna wait for some consensus before I try and order one. Cause maybe my thoughts are wrong lol.

Thanks y'all! Picked this TV up for $50 to take a chance on it. Night!

[lotas]

Re: qn75q70rafxza suiciding samsungs

Yes, you have an STM32F446 controller, as I wrote above, it is powered by 3.3v.

[Diah]

Re: qn75q70rafxza suiciding samsungs

Diah do you mean

no need to do the other test.... your reset from S.M enough... work on the LED driver to the testing points (9802 ( No 1 read less as 3.3V ..
i think its feed rail belong to IC 9801, but you need to follow it after take out the boards... check if this test point had any direct points to any of sockets like FB or from MB.. if not then it mean you have DC to DC on the boards supply this 3.3V... and if t goes as 1 thought to IC 9801, then mean the IC drops it.. so it should be warming..

[EazyBone]

Re: qn75q70rafxza suiciding samsungs

no need to do the other test.... your reset from S.M enough... work on the LED driver to the testing points (9802 ( No 1 read less as 3.3V ..
i think its feed rail belong to IC 9801, but you need to follow it after take out the boards... check if this test point had any direct points to any of sockets like FB or from MB.. if not then it mean you have DC to DC on the boards supply this 3.3V... and if t goes as 1 thought to IC 9801, then mean the IC drops it.. so it should be warming..

I can't exactly find where it goes yet. But nothing on board gets warm at all

[Diah]

Re: qn75q70rafxza suiciding samsungs

I can't exactly find where it goes yet. But nothing on board gets warm at all

you have on the boards many Regulator... with beep ton check the PIN 1 with them.... one by one

[EazyBone]

Re: qn75q70rafxza suiciding samsungs

you have on the boards many Regulator... with beep ton check the PIN 1 with them.... one by one

This is connections I have

[Diah]

Re: qn75q70rafxza suiciding samsungs

read the resistance of PT9801. then left one legs out of PT9801 and check if the V increase on the Regulator to 3.3V

[EazyBone]

Re: qn75q70rafxza suiciding samsungs

read the resistance of PT9801. then left one legs out of PT9801 and check if the V increase on the Regulator to 3.3V

Ohms is 3.2 pt9801

And is this the regulator in the picture? If so there is no increase to 3.3. I dont know if that's the regulator. Like a mosfet

And I thought the forum shut down lol couldn't access it

[Diah]

Re: qn75q70rafxza suiciding samsungs

Ohms is 3.2 pt9801

And is this the regulator in the picture? If so there is no increase to 3.3. I dont know if that's the regulator. Like a mosfet

And I thought the forum shut down lol couldn't access it

can you read whats written on the one like Mosfet ?
PT9801 from the sign black line look like zener diode 3.3V .. but i am not sure,,, this why i asked you to free on legs of it... then see the PIN 1 will be zero V. if this case we can DiY Regulator 3.3V .. can be find easily if you have programmer CH341A ( had one. just we feed it with 5V or less and take out 3,3V to feed pins 1..

PT could be mean Power Train..... or Power transport... LOL

[lotas]

Re: qn75q70rafxza suiciding samsungs

PT9801 - It could be Surface Mount Resettable PTCs.

[Diah]

Re: qn75q70rafxza suiciding samsungs

PT9801 - It could be Surface Mount Resettable PTCs.

you mean a PTC Thermistor ?

[lotas]

Re: qn75q70rafxza suiciding samsungs

you mean a PTC Thermistor ?

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

[Diah]

Re: qn75q70rafxza suiciding samsungs

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

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