Sony KDL-32L504 No Power ....Dead

[tom66]

Re: Sony KDL-32L504 No Power ....Dead

STBY3.3 seems to be at fault.

Can you try again to measure it without the main board connected and see if it stays up?

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

hi,

i removed the connector CN6201 between the power-supply board and what i guess is called the video/logic board.

I then powered on the TV and i measurd the voltage on the STBY pin and it was 3.3V.......and it STAYED at 3.3V DC..........

does this mean the problem is with the logic/main board........i still have yet to check the on/off button............

[tom66]

Re: Sony KDL-32L504 No Power ....Dead

It does seem to point to it. Maybe the main board is loading it down too much. Can you get hold of a 3V light bulb? This will be able to load down the power supply a little. If the light bulb remains lit, it is most likely the main board at fault in some way, as it shows the power supply is capable of maintaining the output required.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

i can look for a 3V lightbulb........but how would i wire it .........

Would i wire one lead from the 3.3V STBY pin to one lead of bulb
and then one lead from "ground........chassis" to the other lead of the bulb?

is this how i would do it?

[tom66]

Re: Sony KDL-32L504 No Power ....Dead

You would need to solder some leads to it. Then place one lead in the STBY 3.3V pin and the other on the chassis of the TV (ground)

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

i looked through all my bulbs and no 3V bulbs..........

[tom66]

Re: Sony KDL-32L504 No Power ....Dead

Can you get hold of a 10 ohm, 5W resistor? You might need to buy one...

Or you might be able you use an LED with a 330 ohm resistor, but it won't discharge the 3.3V very quickly, so might not be obvious.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

i have

1 Ohm-10Watt

and

10 Ohm-1Watt


will either of these work?

[tom66]

Re: Sony KDL-32L504 No Power ....Dead

10 ohm 1W would be fine...

Power dissipated = (3.3^2) / 10 = 1.089W. Slightly over but shouldn't be an issue for a simple test.

It will get hot, but you only need to use it for a few seconds to see if 3.3V is stable or not.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

ok, just wanted to double check something.

I going to wire one end of the resistor to the 2.3V STBY pin and the other end of the resistor to gnd.......the chasis?................

[budm]

Re: Sony KDL-32L504 No Power ....Dead

Try heating up using hair dryer those start-up caps for this 3.3V standby power supply or replace them to see if it will be able to handle the load.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

i will try heating with a hair dryer.....i will also see if i have any spare caps laying around. Can you elaborrate on why using a hair dryer or replacing caps may work......i will try it but just want to learn a little on why.

I did have a question about putting a resistor on the 3.3V-STBY pin. By doing this why is the voltage going to stay at 3.3V?

[tom66]

Re: Sony KDL-32L504 No Power ....Dead

Hair dryer heats up caps.

Capacitors work better when heated... here, I got a Samsung LCD to start up:
https://www.youtube.com/watch?v=Ggn_ggaPvc4&t=2m35s

[selldoor]

Re: Sony KDL-32L504 No Power ....Dead

ok, just wanted to double check something.

I going to wire one end of the resistor to the 2.3V STBY pin and the other end of the resistor to gnd.......the chasis?................

Tom - I think he wants you to confirm where to wire in the resistor

[tom66]

Re: Sony KDL-32L504 No Power ....Dead

Sorry... Yes, 3.3V STBY to ground. Then check if 3.3V STBY is stable.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

thanks guys........i will try the measurement once i get home from work.

Tom, just curious why you think the caps that you showed in the pic might be bad......again trying to learn something.

[selldoor]

Re: Sony KDL-32L504 No Power ....Dead

I think it was budm that suggested heating and posted the pic?
The 3.3v that you are dealing with is supplied via the startup caps. One reason the voltage could be low. variable or non existant could be that these caps have failed.( They have to work quite hard everytime the monitor is switched on. If the voltage is low or variable, heating the cap can sometimes make it work a bit better - till it cools down again.

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

quick question about the caps: I may have replacement caps to try out..........from the previous pic it is hard to tell if i am to replace/test 3 caps or 2.

[tom66]

Re: Sony KDL-32L504 No Power ....Dead

Just do the resistor test first, then apply heat. If heat improves the situation, the capacitors are the prime suspect...

[Welchs101]

Re: Sony KDL-32L504 No Power ....Dead

ok, finally got around to making the resistance measurement.

Here is what i did.

On the 3.3V STBY node.........i soldered a wire that went to one leg of the resistor. THe other end of the resistor i left open...ie...not connected to anything. I plugged in the power to the tv.....then I measured the voltage at the 3.3V STBY node with ........i measured the voltage and it was indeed 3.3V.

I unplugged the power to the TV. I waited a few min then i connected the other leg of the resistor to ground.....as per the instructions.....

I then plugged the power on to the tv.......the voltage at the 3.3V STBY node......measured 0Volts at all times. It never reached 3.3Volts.

I disconnected the power to the TV ........i removed the resistor .............i plugged the power back to the TV but this time the voltage did not go to 3.3V. I removed the power to the TV........waited 15min and then plugged power back to the TV (with resistor NOT connected)......and now the voltage at the STBY node did go back to 3.3V..........


not sure what all this means.............i can tell from the original discussion that with the resistor in the circuit we were trying to see if the STBY node would remain at 3.3V....well it did not.......but i am wondering if this was really a good test............the resistor was a 1-ohm resistor (10Watt)...was this big enough......plus connecting the other lead of the resistor to ground.....was this a really good idea.........not sure ...........

thoughts?