Sony - KDL-32EX400 trouble shooting no turn on

[Doc38343]

I am trying to figure this out. My brother in law said he thinks it was a power surge from a storm that got it.
I have been trying to test the boards but when i looked this one up in Google I found a place that said it was the main board.
Here is my dilemma... I think it is the power supply because the ONLY voltage coming over to the main board is 3.3v and that is on 2 leads only ALL the rest are 0000v.... (photos attached)
Now I could assume the main board sends voltage signal back to the power supply to trip mosfet and relays..
But I just think it is a bad power supply because the 12v raid is not live on the cable as well as it seems odd for it to function in the way described.

So time to ask the experts... trying to learn more so Thanks in advance.

Doc

[budm]

Re: Sony - KDL-32EX400 trouble shooting no turn on

The stby 3.3V is an always on power supply to keep the main board alive when TV is switched off, when power switch is activated, the main board will send the command on signal to 'POWER ON' pin of the power supply board connector CN6401 to turn on the 12V power supply, the 24v power supply, the main board will also send the BL-ON signal to turn on the Backlights, and the T-CON on signal to turn on the VCC-12V for running the T-CON board.
Check the TWO YELLOW FUSES PS6401, PS6402.
Take the DCV (REF. to chassis GND) readings of all the pins of the connector CN6401 when TV is not switched on and when it is switched on.
Make sure to give ALL the pin names next to the Voltage readings so we can see what Voltages are missing.
Pictures provided by SHOPJIMMY.

[Andrew F. Ali]

Re: Sony - KDL-32EX400 trouble shooting no turn on

Look at CN6401-the connector from the Power Board to the Main Board. It should read as I have below. Take Vdc measurements and lets see what can be done.
Pin - Function - Measured DC Volt
1 = Standby -
2 = AC Off Det -
3 = Power On -
4 = Audio 12v -
5 = Audio 12v GND -
6 = Reg12v GND -
7 = Reg12v GND -
8 = REG12V -
9 = REG12V -
10 = BL-ERR -
11 = BL-On -
12 = Dimmer -
13 = NC
14 = T-con-VCC 12v -
15 = T-CON-ON -
Actually you may be getting 3.3Vdc on Pin 1-Standby, which is good. If you are, then follow this test to check if the Power Board is bad:
1. Disconnect the CN 6401 connector cable from the Power Board (This goes to the Main Board)
2. Connect a 100ohm 1/4W resistor across Pin 1-Standby and Pin 3-Power ON
3. Connect another 100ohm 1/4W resistor across Pin 1-Standby and Pin 11-BL-ON
If the Back Lights come ON then you have a Main Board problem

[Doc38343]

Re: Sony - KDL-32EX400 trouble shooting no turn on

Thanks...
Yes sir the yellow fuses are good and best I can tell every component on the PS board is as it should be. Tested all diodes, caps and the mosfets (as able)

After your post I am satisfied it is the main board since it sends no signal out when my wife presses the power for my. (saw a diagnostics on another site as well)

I would like to repair the main board if possible a replacement one is listed from $50 to $130 online......
I am fairly convinced the power surge / lightning spike came thru the catv line and in thru the tuner... there is no visable evidence I went over it front and back with a magnifier.
I have a bench power supply and OScope if I had a bit of guidance I may be able to locate the burnt chip. Lots of SMD's on this board though...
Any input for actual repair trouble shoot?

I gotta go for today a bad thunderstorm is rolling in... pulling the plugs for tonight.

Thanks
Doc

[Doc38343]

SOLVED::Re: Sony - KDL-32EX400 trouble shooting no turn on

UPDATE:
Ordered a main board, waited for a deal to come by.
Works like a charm.
Beautiful very high resolution picture on this model. I am EXTREMELY happy i decided to fix it.

Very good quality TV.