Sony OLED XBR65A8G no video, PSU problem?

[ceak]

Hi, I bought a defective OLED Tv thinking I would just replace the defective board and make it work. The problem was that the TV would turn on with sound but no image. I replaced the TCON first, didn't do anything so I replaced the main board and psu boards too but to my surprise the problem is still there.

So I began testing the PSU to see if at least all voltages were good. What I found is that all the voltages seem good (standby, AC_On, TCON_12v and PWR_On). The missing voltages seem to be EVDD and I'm not sure if BL_ERR should be high or low and if EVDD_ON should be just a pulse or a steady 3.3v.

The EVDD is present for a second, when the tv turns on (there is a relay that clicks) but then it vanishes.

I think that if I can find why this voltage dissapears (maybe there is a bad cap or short circuit?) It would fix that black screen issue.

I don't have the service manual which would be very handy so any help is appreciated.

here's a picture of the power supply.

[canadaboy25]

So the EVDD voltage behaves the same with both the original and the replacement boards? It seems unlikely you would get a defective replacement with exactly the same fault unless it is a pattern failure.

Also, some images of the entire back of the TV showing how all the boards are connected would be helpful.

[Diah]

Originally Posted by ceak

Hi, I bought a defective OLED Tv thinking I would just replace the defective board and make it work. The problem was that the TV would turn on with sound but no image. I replaced the TCON first, didn't do anything so I replaced the main board and psu boards too but to my surprise the problem is still there.

first test:
could you put back all the original boards in place.. and turn it on as you wrote you have sound.. write yours measurements of DC V on the T-CON side reference to TV chassis
1- EVDD Socket ( black color ) on 2 Fuses from both side
2- VIN Socket ( white color ) on both side of Fuse F1

upload photo of the whole back side of the set . to see all boards connected together.

[Diah]

If you got at first test EVDD Lower than 24V then drop down... and the VIN remain at 12V or also drops down ... then do the next

Second Test: ( running the power boards and the panel as stand alone )

1- disconnect the Main boards totally from Power boards and from the T-CON ( mean disconnect the socket coming from the power boards & disconnect the 2 LVDS between Main boards and T-CON .. unplug them from T-CON Side )

2- Disconnect the T-CON from Power boards ( unplug 2 sockets VIN & EVDD )

3. RUN POWER BOARDS as Stand alone ....
make bridge with R value 100 to 1K Ohm ( if the STBY 3.3V you can do it direct with out R but need to be sure 100% of the pins label )
A- STBY & Power_ON ( this will turn on REG12V ON )
B- STBY & TCON_12_ON ( this will turn on TCON_12V ON )
C- STBY & EVDD_ON ( this will turn on EVDD V On Max 24V )

if you confirmed all 3 Voltage in A,B,C you have ... then complete

4- RUN The panel Module as Stand alone
A- Feed the T-CON with VIN & EVDD V which you got at above points B & C

yours panel now should turn on and displaying self test color pattern... give notice on any corner of the screen if there are open cells / dead pixel / Lines...etc.. show us the result

Important: If the panel displaying more than unusual distributed white area image..plug the set out from wall socket immediately.

with my poor English hope this easy explanation enough to you... Good Luck

[ReeceyBurger123]

Originally Posted by Diah

If you got at first test EVDD Lower than 24V then drop down... and the VIN remain at 12V or also drops down ... then do the next

Second Test: ( running the power boards and the panel as stand alone )

1- disconnect the Main boards totally from Power boards and from the T-CON ( mean disconnect the socket coming from the power boards & disconnect the 2 LVDS between Main boards and T-CON .. unplug them from T-CON Side )

2- Disconnect the T-CON from Power boards ( unplug 2 sockets VIN & EVDD )

3. RUN POWER BOARDS as Stand alone ....
make bridge with R value 100 to 1K Ohm ( if the STBY 3.3V you can do it direct with out R but need to be sure 100% of the pins label )
A- STBY & Power_ON ( this will turn on REG12V ON )
B- STBY & TCON_12_ON ( this will turn on TCON_12V ON )
C- STBY & EVDD_ON ( this will turn on EVDD V On Max 24V )

if you confirmed all 3 Voltage in A,B,C you have ... then complete

4- RUN The panel Module as Stand alone
A- Feed the T-CON with VIN & EVDD V which you got at above points B & C

yours panel now should turn on and displaying self test color pattern... give notice on any corner of the screen if there are open cells / dead pixel / Lines...etc.. show us the result

Important: If the panel displaying more than unusual distributed white area image..plug the set out from wall socket immediately.

with my poor English hope this easy explanation enough to you... Good Luck

Very good info thank you

[ceak]

Thanks for the detailed walkthrough Diah, this is exactly what I wanted to do but somewhat wasn't able to achieve (testing boards individually).


So I bridged the pins with the standby voltage and got the right EVDD and TCON voltages. I then plugged in the VIN and EVDD cables in the TCON and got that weird red line on the screen instead of the color test.

Bad panel?

[Diah]

early to judge on the panel.. fault T-CON could cause this lonely line.
keep the bridge as you did before.. (main boards always out from circuit ). remove the metal shield covered the t-con.

check as i wrote in first test points 1 & 2 . test the fuses from both sides.

upload focused high resolution photo of yours t-con

[ceak]

The two fuses on the EVDD side have 22.06V on both sides and the VIN fuse is 12.5V

[Diah]

Originally Posted by ceak

The two fuses on the EVDD side have 22.06V on both sides and the VIN fuse is 12.5V

keep the bridge test until you have complete screen..

unplug the 4 ribbon cable from T-CON SIDE. then turn on.. test if EVDD remain have 22.06V or it increase to 24V. ( we have heavy load on this line )

[ceak]

So I unplugged the 4 TCON Ribbon connectors, voltage stays at 22.07.

On a side-note, afterwards I unplugged the TCON from the PSU to see if I had a higher 24V EVDD directly on the PSU nothing was plugged in and it looks like it's some kind of "pull up" because the EVDD voltage on the PSU is 0 unless the TCON is connected.

[Diah]

Originally Posted by ceak

So I unplugged the 4 TCON Ribbon connectors, voltage stays at 22.07.

On a side-note, afterwards I unplugged the TCON from the PSU to see if I had a higher 24V EVDD directly on the PSU nothing was plugged in and it looks like it's some kind of "pull up" because the EVDD voltage on the PSU is 0 unless the TCON is connected.

this cant be...
take out the PSU from tv and do the test as my post #4 point 3 A,B,C all together

[ceak]

Ok, I found out it was a ground problem, I hadn't put all the screws on tht PSU and when I did it fixed the problem of the missing 24v when the TCON was disconnected.

So just to go back a step, here are the voltages on the PSU alone, with nothing connected:

TCON_12V: 12.73v
EVDD: 22.08

Voltages on the fuses on the TCON when connected to PSU but 4 x flat cables Disconnected from the screen:

VIN:12.67V
VDD: (Both fuses, both sides): 22.08V

Voltages on the fuses on the TCON when connected to PSU but 4 x flat cables Connected the screen: (gives vertical red line at center of the screen)

VIN: 12.6
VDD: (Both fuses, both sides): 22.07


**And REG12V is at 12.6 with or without the TCON connected to the PSU

[Diah]

t-con need to replace..

[Diah]

you can try heating the main IC of T-CON and iC U3 heat them very well with hot air gun... and check only with test bridge to see if the screen became full display

just for warning.. dont heat them and the set in stand position LOL... put the t-con out side on surface and dont move it until they cool down

[ceak]

Thanks, replacing the T-CON is the first thing I did when I got the TV and it didn't fix the problem. I'm really afraid that it's the screen that's defective, can you think of anything I can do to confirm it's the TCON and not the OLED panel itself? I'd order another TCON but I feel it's going to be another 100$ thrown out the window.

*** I tried heating the ICs without luck

[Diah]

Originally Posted by ceak

Thanks, replacing the T-CON is the first thing I did when I got the TV and it didn't fix the problem. I'm really afraid that it's the screen that's defective, can you think of anything I can do to confirm it's the TCON and not the OLED panel itself? I'd order another TCON but I feel it's going to be another 100$ thrown out the window.

*** I tried heating the ICs without luck

then dont... but the panel and t-con at stand alone test showing the line... are you saying when it turn on and can hear sound you have the same line on the screen??? or blank or dimm

did you have access to the panel edge boards for more checking ?

[ceak]

When I turn on the TV, I get the red line in the middle and I can hear the sound (music from demo mode). It's the same red line that i get in the standalone test.

I can dissassemble some more parts to get access to the edge boards I guess, just let me know what to look for

[Diah]

Originally Posted by ceak

When I turn on the TV, I get the red line in the middle and I can hear the sound (music from demo mode). It's the same red line that i get in the standalone test.

I can dissassemble some more parts to get access to the edge boards I guess, just let me know what to look for

LOL this is the first time you write it.. then you had spared us much time.. and no reason to write if PSU problem

if you can access to the edge boards am sure you will discover visual issue. let see.

[ceak]

Ah! Sorry, I thought I mentionned it: when I turn on the tv there is the thin red line for a second (while EVDD is present) and then it dissapears when EVDD goes away and the screen is all black and I can hear the sound. I felt it was a psu problem too.

I'll take everything apart and let you know if i see anything.

**any way to show me what you mean by edge boards?

[Diah]

Originally Posted by ceak

Ah! Sorry, I thought I mentionned it: when I turn on the tv there is the thin red line for a second (while EVDD is present) and then it dissapears when EVDD goes away and the screen is all black and I can hear the sound. I felt it was a psu problem too.

I'll take everything apart and let you know if i see anything.

**any way to show me what you mean by edge boards?

sorry its my fault i didn't noticed you wrote about the line before..

edge board the panel PCB board where the 4 ribbon connected