sony kdl-32bx300 in undefined state

[weeb0]

Hello,

I have a 6 years old Sony KDL-32BX300 32" LCD TV.

I do not have a lot of experience in TV repair, but I can read schematic and understand what is going on.

Few years ago, 1 bad video card from a computer destroyed the HDMI port 2. When I measure the resistance of one of the HDMI signal, it is shorted to GND (4ohm resistance). The problem is inside the ARM processor.

Then, last week, while listening a movie on my PS4 the TV stopped working.

I have unplugged the tv from the wall outlet, let it sit for few minutes and replugged in. Now, there is 2 LED active. Power On is green and no picture is also green. Both LED are solid lit.

Sometimes, both LED will shutdown after 30s, sometimes the LED will stay lit.

Sometimes, when I unplug the TV and replug fast, the No picture LED will be lit orange, that means the TV is in standby mode.

by pressing any key on the button panel or the remote control will change anything.

I tried to reset the TV with the special command ( volume + and power on the TV ) this is not working, I also tried the up + power and it is not working.

I have measured the voltage on the PSU and everything seems to be OK.

The voltage to the inverter are OK ( 25V / GND and signal from the control board ) The inverter error is hi -> OK (there is a pull-up on the controller board)

The 3.3V standby is there and when I plug the controller board I have the following signal from the connector :

standby 3.3V
AC-OFF-DECT 2V (OK there is a voltage divider)
Power_on 3.3V
AUDIO_12V : 12V
REG_12V : 12V
BL_ERR : 3.3V
BL_ON : 0V
Dimmer : 25mV or 1.6V it will depend. I don't understand why this will vary.
T_CON 12V : 0V
T_CON_ON : 0V

if I unplug the controller board, most of the signal are gone, the only signal available is 3.3V stand by. So I am 100% sure the power supply is ok.

So I understand that the TV is powered on but since it is in no picture mode, it will disable the T_CON.

I have looked ad most of the voltage regulator (U10, U27, U29, U1, U34 [taken on L1] and U2 [taken on L2], U24, ).

Q10 is OK to provide 5V power.

USB is powered on

I have measured the voltage from the power button (from the TV) and the voltage is ok.

So I am totally screwed.

From this forum, I have seen that it is possible to get a corruption in the eeprom. I would not be surprised this could be the case. I have a knowledge in I2C manipulation, so I could remove the eeprom chip (U5 chip) and erase it. But I am sure there is information registered in this chip that may total the TV.

If I short the SW1 (reset) switch, there is 18mA going through the switch and the LED are powered off. When I release the LED are lit or powered off in the same state than before.

So, as I said, I am totally screwed. I don't know where to look at, since the signal to enable the T_CON come from directly the ARM processor. I guess the problem does not come from the electronics but seems to be a logical error in the processor.

So, what can I do next ? Purchase a new controller board ?

From what I have seen on ebay, all of the pcb have a T_CON connector different of mine. But I think I should be able to unsolder my connector and put it on the new board. Since the pcb is the same (with the same REV number) I guess the value of the resistor will not change on the pcb, only the connector will change ?!

Thank you for your hints/help.

Weeb0

[weeb0]

Re: sony kdl-32bx300 in undefined state

Also, this TV cost me 338$ so I am not willing to put a lot of money (maybe 100$) on it and before purchasing a replacement board, I will want to be 100% sure it will be a perfect fit.

This is Why I was looking for an internal electronic problem.

Thanx :-)

[dick_barton]

Re: sony kdl-32bx300 in undefined state

Looks like T_Con_On is not switching the 12V onto the Tcon board so you would need to follow back this signal line. T_Con_ON may possibly switch a mosfet which has failed that should supply the 12V to the TCON board.

Found this:-

[weeb0]

Re: sony kdl-32bx300 in undefined state

Hi Dick,

Thank you for your answer and the service manual. I have looked at the schematic and the signal T_CON_ON is powererd directly from the processor. There is only a resistor between the connector and the processor.

Anyway, for me it is ok the T_CON_ON is 0V. Looking at the state of the LED, the picture is off, that means that the TV is in power safe mode having only the sound. But there is no sound.

Thank you !

[Diah]

Re: sony kdl-32bx300 in undefined state

from yours measurement at OP it tell the fault
BL_ERR : 3.3V
BL_ON : 0V
Dimmer : 25mV or 1.6V it will depend. I don't understand why this will vary.
T_CON 12V : 0V
T_CON_ON : 0V

MB switch T-CON off, BL Off because there are errors at BL.

[CapLeaker]

Re: sony kdl-32bx300 in undefined state

check your backlight inverter first.

[weeb0]

Re: sony kdl-32bx300 in undefined state

Diah : the signal BL_ERR seems to be ok, there is a pull-up on the controller board. So, the BL_ERR is pulled down when in error.

Also, on this TV model, the LED will have a blink code to indicate there is an error.

How should I test the backlight inverter ? Should I disconnect the controller, then pull to 3.3V the POWER_ON pin and the T_CON_ON signals ?

Thank you!

[Diah]

Re: sony kdl-32bx300 in undefined state

if you think the BL ERR seem okay, then you should be able to go from stand by state to view SCDL Self Check Diagnostic List.

when it in stand by Press the following buttons on the Remote Commander within a second of each other Display, 5, Volume-, Power

[budm]

Re: sony kdl-32bx300 in undefined state

Can we see the whole back side of the TV so we can see all the boards and how they are connected together?
There are many version of this TV.
http://www.shopjimmy.com/catalogsear...ny+kdl-32bx300

[weeb0]

Re: sony kdl-32bx300 in undefined state

Guys, I will post picture, hopefully this night. Now, since my last tests, the TV set will not start up. The POWER_ON stay off.

I guess the controller board is dead. Also, the processor get hotter than normal, probably there is a short somewhere that kills it.

[weeb0]

Re: sony kdl-32bx300 in undefined state

Guys,

Attached to this post you can see the picture of the TV.

I added picture of the controller board.

I can see something strange on the pcb. There is white paint on few components near the power supply output cable (solder side). Anyone knows why they do that ?

Thank you

[budm]

Re: sony kdl-32bx300 in undefined state

I would test the power supply inverter by removing the cable between the power supply and the main board, then use 1K resistor between 3.3VSBY pin and the Power on pin, resistor between 3.3V and the BL-ON pin to see if the backlights will come on, if not, you may also need the resistor between 3.3V and the Dim pin.
You should also make sure you do have boosted Voltage close to 400VDC between the two legs of the main filter cap in the Hot side.

[weeb0]

Re: sony kdl-32bx300 in undefined state

Hello Budm,

I have removed the BL_ON wire from the wire harness connected to the controller and added a 1k resistor between this wire and 3.3V standby. When I power on the TV, the backlight is lit. :-)

btw, I don't know why, but finally the control board is no more dead as I told in another thread. It is working as I have explained in my first post.

Also, I tried the DISPLAY, 5, VOL - and power is not working.

To be sure my remote control was working, I looked at it via a camera, the IR LED is blinking when I press the button...

As it is written in the training manual, the TV must be off. But in my case, the TV is powering on as I plug in in the wall outlet. This behavior makes me think the eeprom is corrupted.

Thank you for the suggestion !

[weeb0]

Re: sony kdl-32bx300 in undefined state

I have tried something wild...

I have shorted to GND the SDA line of the system eeprom.

Sadly, no change.

[weeb0]

Re: sony kdl-32bx300 in undefined state

To recap my problem / findings :

1. The power supply is good
2. The inverter is OK
3. The T-CON is probably working. The same bahavior occur if the T-CON connector is connected or not. Also, there is no sound coming from the TV.
4. The TV is always powered on (or not)
5. The TV will react to absolutely no user input (key / remote control)
6. I have shorted out to GND the line SDA of the main EEPROM, so we can be sure the problem is not from a corrupted eeprom.

So, we can be sure the problem is the control board ("A" Board).

The model number of the control board is 185761121 REV 1.0 which is not easily available or the price is too much. More than 100$ USD is too much to save a 300$ CDN TV.

But, I would like to "refurbish" the controller board.

My plan :
1st : I will look for bad diode that could short the processor signal lines
2nd : I will monitor the i2c bus to see if there is activity
3rd : I will monitor Flash to see if there is activity

What are you thinking about this plan ? should I look at other component first ? It is my first time trying to debug a TV controller card.

Thank you a lot for your help !

[dick_barton]

Re: sony kdl-32bx300 in undefined state

Have you read through the earlier threads covering this model on this site where there is quite a bit of information.

[weeb0]

Re: sony kdl-32bx300 in undefined state

Hi Dick,

Yes I did read through the earlier threads.

No other people had the same behavior that I can see. Also, all other changed the module or trashed the TV.

With your help, I know the problem is within the controller board. Now, I would like to find the problem on the controller board.

Thank you for your suggestion.

[weeb0]

Re: sony kdl-32bx300 in undefined state

I am working sniffing out the main i2c bus. There is not a lot of data transfert ...


What is very, very strange is when I short scl line to gnd, I can see some activity on the bus, even if it is tied to GND .... and the LEDS are blinking ... sound like a short ! Does my scope is stupid ?! maybe ...

anyone has already this problem ?

[weeb0]

Re: sony kdl-32bx300 in undefined state

I guess the I2C is only a symptom of a bigger problem.

Anyone know where I could get the datasheet for the processor mediatek mt5388JFMG ?

I would like to understand it's inner working

ie. when the TV bootup, how does it know it has to power on / stay in standby ?

and in fact, when the signal power_on is pulled high ? When the TV is powered on or when the TV is in stand by ? If power_on is low on standby, the memory (NAND, FLASH & EEPROM) are disabled. So, how does the ARM Processor can load it's program ? Is there any internal ROM/flash/prom on the processor ?

I have a lot of questions and would like to read the datasheet to see what is embedded in the processor.

Thank you

[victor_cj]

Re: sony kdl-32bx300 in undefined state

Try to write the software from the nand flash memory with a universal programmer.
Sony KDL-32BX300 H27U1G8F2B.bin https://www.xfile.ro/jhWQg0d&a=1e996...1eda58ed1fb880