Sony KDL-32WD600

[bootpanic]

Hi everyone,

I have a Sony KDL-32WD600 which is completely dead, no power led, nothing...

The problem has something to to with the control circuit for powering the TV on. When i bridge source and drain of the FET that is switching the 19,5V from the mains adapter to the DC/DC converter the TV is powering on and working normally.

Service manual and or schematics would be a great help.

Thanks in advance!


Cheers!

[yokoono]

Re: Sony KDL-32WD600

What is the power code ?.

[bootpanic]

Re: Sony KDL-32WD600

What do you mean by "power code"

Here is a picture of the label.

[yokoono]

Re: Sony KDL-32WD600

You did not specify that it is external power supply. To be easier to find, you must then specify the main code.
Are you sure the external power supply is ok?

[bootpanic]

Re: Sony KDL-32WD600

You did not specify that it is external power supply. To be easier to find, you must then specify the main code.
Are you sure the external power supply is ok?

Yes i am sure the power supply is not the problem. I have powered it from a bench power supply with the same effect.

When i bridge the source and drain from the FET (TPC8129) that's sitting in front of the incoming 19.5V the tv powers on and is working normally.

PS: The red (visible in the picture) and black wires are soldered onto the DC power socket for powering it from my bench power supply as i don't have a spare 6.5/4.4mm DC plug.

[yokoono]

Re: Sony KDL-32WD600

The mosfet order comes from the processor. It may be a imperfect contact to the processor or a software alteration.

[bootpanic]

Re: Sony KDL-32WD600

The mosfet order comes from the processor. It may be a imperfect contact to the processor or a software alteration.

Without schematics it is hard to follow where the gate is going to (read coming from).
I measure -50mV on the gate of the mosfet relative to the positive of the supply voltage which is way to little to turn the mosfet on.

Probing around i did not found any supply voltage going to the processor...

[bootpanic]

Re: Sony KDL-32WD600

I have connected the gate of the MOSFET (TPC8129) over a 10K resistor to ground. Now the TV powers on and seems to be working normally. I can turn the TV on and off, drawing about 10mA when off.

I'm wondering what the exact function of the mosfet would be???

Maybe someone can shine some light on this?

[bootpanic]

Re: Sony KDL-32WD600

Here is a picture of the mainboard.

[R_J]

Re: Sony KDL-32WD600

If the mosfet is used to control the 19 volts, there must also be a regulator somewhere that supplies the microprocessor with standby voltage, It could be that that regulator is not working. When you turn the tv off you are likely only turning off part of the tv's circuits. Have you checked all the small fuses on the board?
With the resistor in place on the gate, does the fet turn OFF when the tv is turned OFF or is there still 19 volts on the drain and source?

[will62]

Re: Sony KDL-32WD600

Take a look at the attached SM. Slightly different model, but power section layout looks similar. Perhaps you can use it to help you track down your 5V standby.

[bootpanic]

Re: Sony KDL-32WD600

If the mosfet is used to control the 19 volts, there must also be a regulator somewhere that supplies the microprocessor with standby voltage, It could be that that regulator is not working. When you turn the tv off you are likely only turning off part of the tv's circuits. Have you checked all the small fuses on the board?
With the resistor in place on the gate, does the fet turn OFF when the tv is turned OFF or is there still 19 volts on the drain and source?

Yes, all the small fuses seems to be OK.
No, the mosfet stays on all the time with the 10K resistor connected from GND to the gate (19,5V present at PIN5-PIN8 of the fet when TV is off).
The TV only draws 10mA from the 19,5V supply when off.

[bootpanic]

Re: Sony KDL-32WD600

Take a look at the attached SM. Slightly different model, but power section layout looks similar. Perhaps you can use it to help you track down your 5V standby.

Thank you very much!
This SM helped me a great deal in narrowing the problem

[bootpanic]

Re: Sony KDL-32WD600

I'm not sure the fet is actually controlled by the processor. There are 2 other transistor like devices in the protection circuit. When the TV is off with the 10K resistor on the gate of Q6020 present it draws only 10mA...

I'm suspecting the SMD marked 31. When following the "Protection Circuit– Checking Procedure" in the SM it boils down to Q6019 damage...

I think there is a good chance that the SMD marked 31 in the picture might be Q6019. If Q6019 is a normal transistor it certainly is broken, got some weird high values with DM on diode test.

There is as far i can find no mention of the type of Q6019 in the SM. Does anybody know what type it might be?

[will62]

Re: Sony KDL-32WD600

Here's a data sheet for a PNP that has a marking code 31.

[bootpanic]

Re: Sony KDL-32WD600

Here's a data sheet for a PNP that has a marking code 31.

That looks like a good candidate!

Just ordered 10 of those.

Thanks!

[budm]

Re: Sony KDL-32WD600

Did you check the junctions of that PNP Transistor to see what they show? Check the Voltage readings?