Sony KDL-46EX505 No T-con Voltage

[Crystaleyes]

Hi all,

been asked to look at a friends old Sony which turns on ok, changes channels and has backlight and volume control etc. yet just displays grey, with a few streaky lines across the screen.

A quick test revealed that the voltage across the T-Con cable connector(CN6151) on the PSU (G2) was missing, although the 3.3v 'T-CON_On' and 'T-CON_Vcc12v' were present at the connector which links to the main board (CN6150).
As they live some distance away I took the PSU with me to see where the problem might lie.



I'm presuming that the 3.3v needs to be connected to both the 'POWER_On' and 'T-CON_ON' in order to for the area in question on the board to stay 'live'?
There is not a lot of circuitry between the two connectors, with a FET and a couple of transistors after the secondary of a transformer, but my concern is whether the PSU might be damaged with no load?

I'm not a TV tech but want to know if there is likely to be any problem if I power the board up without any load?

Enclosing the schematic and a couple of photos of the suspect area if anyone is interested

[kasfamily]

Re: Sony KDL-46EX505 No T-con Voltage

As a load, you can use car incandescent lamps, then checking the power supply will be more informative

[Diah]

Re: Sony KDL-46EX505 No T-con Voltage

As they live some distance away I took the PSU with me to see where the problem might lie.

I'm presuming that the 3.3v needs to be connected to both the 'POWER_On' and 'T-CON_ON' in order to for the area in question on the board to stay 'live'?

you are correct about how to run the PCB as stand alone to have t-con 12 and other V to MB socket... but i think you took the wrong boards with you... the issue much at MB. or T-CON or panel.

[Crystaleyes]

Re: Sony KDL-46EX505 No T-con Voltage

As a load, you can use car incandescent lamps, then checking the power supply will be more informative

Yes. Nice one.

Obvious really, but still didn't enter my head,

thanks

[Crystaleyes]

Re: Sony KDL-46EX505 No T-con Voltage

you are correct about how to run the PCB as stand alone to have t-con 12 and other V to MB socket... but i think you took the wrong boards with you... the issue much at MB. or T-CON or panel.

You think so?

Does the T-CON_ON signal not come to the PS board from the main board? Then surely it is the PSU board which powers the T-CON board?

Haven't had time these last couple of days but intend to power up the PSU and see what readings come up.

[dskall]

Re: Sony KDL-46EX505 No T-con Voltage

No you don't need a load to check unless you suspect it can't put out the required current.
T-con are most often powered through the ldvs cable from the main to the t-con on one side of the cable.

[Crystaleyes]

Re: Sony KDL-46EX505 No T-con Voltage

No you don't need a load to check unless you suspect it can't put out the required current.

Thanks.

T-con are most often powered through the ldvs cable from the main to the t-con on one side of the cable.

And I'm sure that there is some power in this cable as the T-CON board gets warm.
There is a second thicker wired cable from the PSU to the T-Con and it is this which has no power.
Hopefully should have time today to connect it up and test it further

[nomoresonys]

Re: Sony KDL-46EX505 No T-con Voltage

yep, when dealing with distance, always take the whole tv whenever possible.

[dskall]

Re: Sony KDL-46EX505 No T-con Voltage

It always helps to have good pictures.

[Crystaleyes]

Re: Sony KDL-46EX505 How to test a T-CON board?

It always helps to have good pictures.

For sure, but only having the one board with me didn't help.

Anyway, fired up the board and the T-CON connector voltages are present and correct at 12v, so it would indeed appear that I am looking at the wrong board.

I'll head back up to the TV in the next few days, but are there specific voltages which can be measured on the T-CON board to confirm whether or not it is working?

[dskall]

Re: Sony KDL-46EX505 No T-con Voltage

vgl, vgh, vcom, vcc's

[Crystaleyes]

Re: Sony KDL-46EX505 No T-con Voltage

Still haven't got back to the TV but considering there are a multitude of lines across a grey screen, judging by what I can find, it may be that the VDA/VSource voltage is missing.

If tht does turn out to be the case, any idea what might cause that to fail?