Sony Bravia KDL-40W5500 backlight issue

[electroman220]

Hello everyone,

I would like to post a question regarding the following TV:

Sony Bravia KDL-40W5500

When I turn on the TV, the indicator LED on the front of the TV turns green for approximately 10 seconds but the screen remains black. Then the TV shuts down and the indicator LED gives an error code by blinking 6 times red.

This error corresponds to a backlight issue.

I opened up the TV and did the following measurements:

CN6701 connector (to balancer board):
* 12VCC
* FB
* FB
* LD
* LD
All these read 0V DC.

All the transformers on the inverter board all read around 0.15V AC.

I would be pleased if you can guide me finding the root cause of this problem!

Thanks in advance.

[Fisher77]

Re: Sony Bravia KDL-40W5500 backlight issue

Can you post some good clear pictures of all the boards in the tv?

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

The service manual of this device can be downloaded here.

This includes schematics and pictures.

[budm]

Re: Sony Bravia KDL-40W5500 backlight issue

We need good clear pictures of your power supply board.
What other Voltages do you have on other connectors of the power supply board?

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

In the attachment you can find the pictures. If they do not suffice, please let me know. I did some measurements. All readings are with TV turned on and are DC voltages.

Connector 1 [CN6154] (connection with logic board):
* NC: 0V
* DIMMER: 0V
* BACK_LIGHT_ON: 2V
* INV_ERROR: 0V
* GND: 0V
* BALANCER_ERR: 0V

Connector 2 [CN6151] (connection with TCON board):
* Reg 12V - GND: 0V
* Reg 12V - GND: 0V
* Reg 12V: 12V
* Reg 12V: 12V

Connector 3 [CN6150] (connection with logic board):
* Reg 12V: 12V
* Reg 12V: 12V
* Reg 12 V: 12V
* Reg 12V - GND: 0V
* Reg 12V - GND: 0V
* Reg 12V - GND: 0V
* UNREG 15V [?]: 0V
* GND [?]: 0V
* UNREG 15V: 15.2V
* UNREG 15V: 15.2V
* STBY3.3V: 0V (3.4V in stand by)
* AC_OFF_DET: 3.4V
* POWER ON: 3.3V

In the last connector, I’m not sure if I read the names correctly for 2 wires (indicated with [?]). The readings for the fourth connector (connection with inverter board) are listed above.

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

Anyone?

[budm]

Re: Sony Bravia KDL-40W5500 backlight issue

OK, so one thing for sure is that you never did see the backlights flash on for seconds, correct? If that is the case we will need to check the inverter section.

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

That is correct: the screen remains pitch black. How do I check the inverter section?

[budm]

Re: Sony Bravia KDL-40W5500 backlight issue

That is correct: the screen remains pitch black. How do I check the inverter section?

We need to find the service manual for this TV or at least the diagram of this power supply/inverter board.
I believe these are the boards for your TV, and it also has repair kit for the board.
http://www.shopjimmy.com/catalogsear...y+A-1660-720-a

Your board is A revision: Sony A-1660-720-A

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

Here is a link to the corresponding service manual.

The diagram of the inverter/power board (IP1 Board Schematic Diagram, A-1660-720-A) can be found on page 33 of the service manual.

What does a revision mean?

So if I understand you correctly, you suggest that there are two options to solve the problem:
1) Buy a new inverter/power board
2) Search for faulty component(s) on inverter/power board and replace them using a repair kit

Which option would you recommend? And how do you approach searching for the faulty component(s)?

[budm]

Re: Sony Bravia KDL-40W5500 backlight issue

Here is a link to the corresponding service manual.

The diagram of the inverter/power board (IP1 Board Schematic Diagram, A-1660-720-A) can be found on page 33 of the service manual.

What does a revision mean?

So if I understand you correctly, you suggest that there are two options to solve the problem:
1) Buy a new inverter/power board
2) Search for faulty component(s) on inverter/power board and replace them using a repair kit

Which option would you recommend? And how do you approach searching for the faulty component(s)?

Once you have the diagram, you will be look to see how the inverter circuit get its Voltages from to run, it should be getting the Voltage from the PFC Voltage circuit, and that Voltage may be fed through the fuse or fusible resistor, so that is the start.

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

I'm trying to understand your suggestion, but I do not succeed. Could you give the specific numbers of the fuse and fusible resistor to check?

[vinceroger69]

Re: Sony Bravia KDL-40W5500 backlight issue

the service manual is too large to attach in the thread
please can you also post some good clear pictures of the boards used in your tv as we can highlight parts we need you too test etc

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

the service manual is too large to attach in the thread

The service manual can be downloaded on the mentioned (external) url. It is not attached to the thread.

please can you also post some good clear pictures of the boards used in your tv as we can highlight parts we need you too test etc

There are pictures of the power board in post #5. I will also take pictures of the other boards.

[budm]

Re: Sony Bravia KDL-40W5500 backlight issue

https://www.badcaps.net/forum/attach...9&d=1483911641
Fusible R6500 (next to C6501) is the fusible resistor (white ceramic body).

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

https://www.badcaps.net/forum/attach...9&d=1483911641
Fusible R6500 (next to C6501) is the fusible resistor (white ceramic body).

I measure 0.4 ohm for this fusible resistor, which is pretty close to the 0.47 ohm indicated in the service manual.

[syaoran123]

Re: Sony Bravia KDL-40W5500 backlight issue

Have you visually inspected under the powerboard? In particular, check under the transformer (top left in pic 1) to see if there's any cracked soldering.

[vinceroger69]

Re: Sony Bravia KDL-40W5500 backlight issue

what voltage do you get on each side of that fuse?

[electroman220]

Re: Sony Bravia KDL-40W5500 backlight issue

what voltage do you get on each side of that fuse?

I measured with respect to the ground and the value for both sides fluctuated between 60 and 80 milli Volts.

Have you visually inspected under the powerboard? In particular, check under the transformer (top left in pic 1) to see if there's any cracked soldering.

I'll check tomorrow when I'm fresh

[budm]

Re: Sony Bravia KDL-40W5500 backlight issue

I measured with respect to the ground and the value for both sides fluctuated between 60 and 80 milli Volts.



I'll check tomorrow when I'm fresh

You are making the DC measurement in the hot side of the circuit so you have to use the negative leg of the main filter cap as the GND ref for your meter, MAKE SURE NOT TO TOUCH ANYTHING IN THE HOT SIDE WITH YOUR BODY OR YOUR HANDS!