SONY KDL-55HX850 : No backlight, no error code, rest OK

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

This is the right ribbon cable from the right screen board, but even trying to squeezing it, putting something behind there are more vertical lines at the same space of screen. Oups ! After seeing more precisely I think this is the black "plastic" bar of the ribbon at his center that may be problematic. However I don't think this is "€€€ rentable"...

Maybe if I found a ~tv with a ~same samsung panel ??

55WQL_Sl6V0.1 is one of the 2 panel board model, (in my phone tv is not reachable to where I live now).
Thanks to Google it may be a LTY550HQ04

[ajshoe]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

pic of display would be nice

[budm]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Ok so I replaced the PSU and the TV works, however there is two lines in the screen, so maybe I broke IT or it was already there, I don't know !

Anyways the PSU was faulty !

So if you check the Voltage per my post #35, what do you get?

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Ok so I replaced the PSU and the TV works, however there is two lines in the screen, so maybe I broke IT or it was already there, I don't know !

Anyways the PSU was faulty !

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Hello all.

The new LEDS are in place.
Nothing seems to be "more broken" after I dissasemble it.

However the backlight still doesn't works

Any others ideas, maybe it's the PSU ? The driver LED seems cold when touching.
With my phone flash I see that the BL is not at 0 in the settings

Thanks and have a good day !

[Diah]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

i don't think its your fault... because heat and the reflector very close to leds surface. just dont forget to clean the edge of the reflector to have clean display..before 3year or more i had got this edge 7030 led. i removed them all with heat gun and placed pasta then stick new ones after all are in place and straight i applied the heat from downside of the strips so all got in place with good middle ground contact.. on aliexpress i got them 100 pieces for about 5$

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Here are the pictures of the led strips.
All 4 are defective now (the first led was "sticked" to a plastic reflector, maybe by heat...

I got a led tester. I put LED + to one of the + of the strips, and with the LED - I go to all - of the strips, each - illuminate 8 leds.

Just one led was already defective it seems, looks cracked. By disassembly it I certainly broke the first leds of each 4 because they were sticked to the reflector, IDK why, there isn't tape.

[budm]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Can we see the LED strips?
What did you use to power up the strips? So how many strips are bad? Two?
BTW, pin 1 Voltage which is the Boost Voltage sensing pin to make sure the PFC Boost Voltage is not too low, it should be > 2V on that pin 1, at 0.1V it thinks that the PFC Voltage is bad so it will stay in protection mode.

[nomoresonys]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Ok, then it looks like it was a bad backlight/s, trying to figure out why it could not be determined by just seeing if there was expected voltage on powerboard at backlight connector with backlights unhooked??

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

So I got some time today to dissasembly it...
It was a nightmare, but I got the 4 led strips. One led was down.
But during disassembly of each, the first led self destruct itself (sticked to one of the reflector layer). When testing the first led never light up (I suppose broken during disassembly) but every other do... except one lost in one strip, it sure be defective befor I didn't touched it.

I'm ordering all 4, I hope I didn't destroyed any other thing (I reassembled it without screws and it seemed ok, even the picture seems ok but not sure if there is any lines... I will see.)

Thanks.

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Hi,

CXD9969AP IC6701
STBY : Pin 1 0.1v - Pin 8 13.8v
ON : Pin 1 0.1v - Pin 8 14v

[budm]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

I found the schematic of how the CXD9969 is used.
Please check the Voltage on pin 1, and pin 8 of the IC against the negative leg of C6530.

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Impossible to find the sheet, maybe this is the same ?
https://www.datasheetq.com/CXD9969P-doc-Sony (lack the A)

[budm]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

I already do it for a samsung 40d5003 (in fact I'm waiting the new leds to come...) but here it's a 55, glass panel in front (strange design even if "beautiful").

SMPS IC : IC6701 ?

Yes, that is the IC, need to look for spec sheet and see if there is error detection pin that will put it into shutdown mode.

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

I already do it for a samsung 40d5003 (in fact I'm waiting the new leds to come...) but here it's a 55, glass panel in front (strange design even if "beautiful").

SMPS IC : IC6701 ?

[budm]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

Opening up the LCD panel is the last thing I would do since if you have never done one you can easily damage the screen, damage the tab bonding.
I will look at the spec of the SMPS IC to do more verification.

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

I retested CN6601 not plugged, meter in place, first turn on, in fact all pins of CN6601 except NC and LD_ERR are -0.01v in stby and goes "down" to -0.02v when turning on.

No flash at all from leds even a micro flash (verified in dark room).

[budm]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

I was hopping that the leds be all good but my hope is going down

Anyway here are the results, if my tests are correct :

Diodes (multimeter to diode mode) D6602, 03, 12, 13:
1.140v 0.425
1.140v 0.425
1.140v 0.425
1.145v 0.423

If I disconnect CN6601 everything is at 0v except 0.7V pin 11 LD_ERR
(startup or not) The TV works fine behind except of course BL

R6707 2.2ohm

Stby C6530 395v, 13.88v with postive on R6707 (the two legs)
TVON same but 14v on the two legs.

Thanks

So there is no action even when the output of the power supply is not connected to the LED driver board, the power supply should put out around 50V, then if there is error the power supply will be shutdown due to error, right now the SMPS IC for the LED power supply is getting the VCC (13V) to run, but no action.
There are many LED strings in this panel and they are driven by many LED drivers, so the one with good LED should at least flash on for seconds before the protection kicks in.
BTW, you did leave the meter in place to monitor VLED pin of CN6601 when TV is turned on to catch the Voltage when TV is first turned on, correct?

[Jojo337]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

I was hopping that the leds be all good but my hope is going down

Anyway here are the results, if my tests are correct :

Diodes (multimeter to diode mode) D6602, 03, 12, 13:
1.140v 0.425
1.140v 0.425
1.140v 0.425
1.145v 0.423

If I disconnect CN6601 everything is at 0v except 0.7V pin 11 LD_ERR
(startup or not) The TV works fine behind except of course BL

R6707 2.2ohm

Stby C6530 395v, 13.88v with postive on R6707 (the two legs)
TVON same but 14v on the two legs.

Thanks

[budm]

Re: SONY KDL-55HX850 : No backlight, no error code, rest OK

No power to the TV:
Check the resistance of R6707.
Turn on the TV and check the DC V between the two legs of C6530, be real careful since you are working on the Hot deadly side of the circuit., then check the DC V between the negative leg of C6530 against each leg of R6707.