Sony Bravia KDL-40EX400 will not power up

[suiramix]

Just another typical case of 3 years old Sony KDL40-EX400 lcd tv which refuse to power up (dead) by pressing the remote or tv set power button … no electronic components damaged or swollen capacitors so far …so I started checking the power supply output voltages .
According to power supply G2HE circuit diagram (attached) at connector CN6101:
pin 1 [STBY 3.3V] = 3.31V
pin 2 [AC OFF DET] = 0V , and everything else is 0V
According to training manual ctv-61, if the tv in plugged in an active power outlet, AC OFF DET should have 3V …so the power supply / IC6301 (CXA3809M) is defective… at this point what other voltages should I measure before replace anything else ?

[budm]

Re: Sony Bravia KDL-40EX400 will not power up

What voltage do you have at pin 3 AC DET IN and at PIN 23 of the IC6301 (Ground ref point at the negative leg of the main filter cap)?
BTW, do you have the link to the full SCH of this TV?

[suiramix]

Re: Sony Bravia KDL-40EX400 will not power up

Hi Budm... thanks for fast reply (btw, big fan of your photobucket pictures) ...so IC6301 has voltage on pin 3=2.68V and pin 20=9.48V
Unfortunately, I have no other schematics of this lcd tv !

[tom66]

Re: Sony Bravia KDL-40EX400 will not power up

You could try as a quick test disconnecting the AC OFF DET wire from PSU and connecting it to STBY 3.3V. Use a 100 ohm resistor in series to protect the main board in case there are any shorts.

[budm]

Re: Sony Bravia KDL-40EX400 will not power up

Pin 23 is the one I need, if that pin is low the LED in the opto will be on which will turn on the photo-transistor which will cause the AC DET to be low and lock out the circuit. Normaly, the AC DET will be high if this is the same detection used in other SONY power supply. Or you can try TOM's method.

[suiramix]

Re: Sony Bravia KDL-40EX400 will not power up

I was doing a lot of reading regarding Sony CXA3809M IC and according to the pdf. datasheet , recommended VCC (pin 20) should be 12 to 18V …sorry for earlier confusion ! Tonight I will measure the voltage at pin 23 !!! Thanks again Budm and Tom!

[budm]

Re: Sony Bravia KDL-40EX400 will not power up

Hmm:
Under Voltage Lock Out Circuit Block (VCC pin)
Item Symbol Measurement conditions Min. Typ. Max. Unit
Turn-on voltage Vact 10.2 11.0 typ. 11.8 V
Turn-off voltage Voff 9.0 9.6 typ. 10.2 V
Hysteresis Vact-Voff Vact – Voff 1.1 1.4 1.7 V

So you have indicated the VCC of pin 20=9.48V.
That is low. Are you getting about 360~400Vdc (measured at the two legs of the cap) on the main filter cap?

[budm]

Re: Sony Bravia KDL-40EX400 will not power up

Please check the DCV on the cap C6117, it should have around 18VDC, if not check the cap and the two Zener diodes.

[suiramix]

Re: Sony Bravia KDL-40EX400 will not power up

Hi BudM....so IC6301 has voltage on pin 23=0.1V...main filter cap C6325 has only 168.3V and C6117 has 10.15V...!!!

[suiramix]

Re: Sony Bravia KDL-40EX400 will not power up

Just a quick update... I did replace C6117 and C6323 with new one, but almost the same voltage reading . Can someone tell me why all the capacitors are rated to 105C except the main one (270uF/450V) which is only 85C and so close to the biggest heat-sink ???

[mixmix]

Re: Sony Bravia KDL-40EX400 will not power up

You solved this issue? i have teh same problem.

[tibimakai]

Re: Sony Bravia KDL-40EX400 will not power up

There is a 40EX500 in this list and it shows a bad CXA3809M IC if the TV it's
dead.
http://www.mikestvtips.com/index.php...le%20Histories
I had a similar issue with a 46" which had a 6x blinking light and it was the mainboard.

[budm]

Re: Sony Bravia KDL-40EX400 will not power up

Oops, wrong thread.

[t4796]

Re: Sony Bravia KDL-40EX400 will not power up

If you have ~10v across C6117 could the mean one zener is short so you're only getting 9.1 (maybe ~10v on your meter) across it?

[t4796]

Re: Sony Bravia KDL-40EX400 will not power up

actually i think the zener are there to protect the ic in case the voltage goes above 18.2v is this right? i can't edit my other message

[coofhair]

Re: Sony Bravia KDL-40EX400 will not power up

Thank for helpfull