Sony KDL-40ex400 LCD tv no power...100% dead

[shelby5041]

hi i have been tinkering with this tv i got..no power 100% dead no lights on front nothing..no backlight....no sound....nothing..no clicks...

have done some research....took tv apart...i do have 3.3v standby voltage from power supply but standbylight not on....'but no other voltages...anywhere

i then ndisconnected the cable to main board and jumpered the 3.3v standby pin to the power on pin on main board end of cable......and i get no voltages anywhere on the power supply board other than the 3.3 standby volatage and obviously 3.3 pwr on volatage

so my question is that if i do have 3.3 standby voltage why do i not get a standbylight???....and i originally thought it was a mainboard issue since soemone said if you get standby voltages but no standby liught ...the main board is the problem and the power supply is good.....well im not sure about that in my case since i have no volatges on power supply other than 3.3 standby ....

any ideas whats going on here??....i highly doubt both boards would go bad at same time

thank you

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

forgot to mention...all fuses on power supply and main board are good..........

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

and all caps look and test good

[tibimakai]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

The main board gives the command to the power supply to turn on.
Usually you need to use some resistor (100ohm-2.5kohm) between the standby and Ps-On pins and nother one between the standby and inverter on pins.
The main board has to be disconnected.
The backlight, should turn on if the power supply, inverter and backlight is good.
You would also have the voltages at the power supply.

[tom66]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

Some PSUs will require you to jumper the power on command to ground. Also you usually need to turn on the backlight independently.

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

well like i said i do have 3.3 standby voltage but no standby light

when i jumper the 3.3 standby voltage to the pwr on pin i get not voltages anywhere on the power supply


according to many tutorials..once you supply power to power on pin that should turn on power supply and all voltages on board should be enabled

is this true?

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

i did not use a resistor i just used a wire to jumper as this has been done on many tutorials........all im trying to do is find out if its a bad main board or a bad power supply

[mmartell]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

As tom said some boards require you to pull PSON to ground so try that and see if you get anything.

[tibimakai]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

You should post some clear pictures, with your power supply board.

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

i dont know what you mean when you say ground pwr on

what i did was take a wire and inserted in 3.3 standby pin and then took the other end of wire and stick it in pwr on pin.........

this should energize power supply...but i still have no voltages on power supply at the pins labeled 12v and 24v

can you be detailed when you say ground the pson....im not a tech or electronics guy...i know some but not much

thanks

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

here are two pics as you can see i have the jumper wire connected from standby 3.3 v to pwr on

im trying to troubleshott if problem is main board or power supply

originally since i get no standby light but i do have standby voltage i would have thought it was for sure main board issue however when doing some tests on power supply i dont see any voltages other than 3.3 standby

so now im stuck

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

tom are you saying for me to take a wire and connect to pwr on and other end to ground '

in addition to having the wire from 3.3 standby voltage to pwr on pin?

[tibimakai]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

I don't think that is a good idea to unplug everything from the power supply.
You should live the board in the TV and unplug only the main board plug.
Use resistors as I suggested, not just wires.
I have just done this on a Vizio TV and I had the backlight turned on this way.
I know now, that have a mainboard issue.

[budm]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

The PS_ON (PWR ON) signal for this board is active HIGH (<1VDC = OFF, > 3.0V = ON).
The main thing you have to ask is that are you getting PS_ON signal form the main board or not.

"i highly doubt both boards would go bad at same time" it is not out of the question at all.

See training manual.
There are many threads on this model that you should read them:
https://www.badcaps.net/forum/search...archid=3863809

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

hi thank u...i have tested power supply in circuit and still no power.....

i had ps in tv.....disconnected ps to mainboard cable at mainboard....jumpered out the present 3.3 standby pob to the pwr on pin
result: power supply does not turn on....no voltages on any pins...no 12v no 24v

is this a valid test?


can someone tell me if this test proves ps is bad or not...

...i dont care about mainboard at this point

and budm i have seen trainong manaul....thanks

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

timibaki accordong to ur reply #4

my ps is bad

bl no turn on...no voltages

when i jumper 3.3 to pwr on

and jumper 3.3 to bl on

would this be correct to say ps is bad?
or am i missibg something with this test?

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

off subject.....im havibg difficult time desoldering the leaded solder on this tv.....already ruined a pad

any basic pointers/advice?

im using a 30w solder sucker with the rubber squeeze end.......does not work

would 60 w iron using braid wick be better?

im novice so please no professional equopment wanted.....

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

correction lead free solder

[selldoor]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

Please can you update your profile with country and mains voltage

[shelby5041]

Re: Sony KDL-40ex400 LCD tv no power...100% dead

per manual....pwr on energized via 3.3v should turn ps switch on and energize all voltages on ps 12v and 24v


mine fails this test