Sony Bravia KDL-37M4000 doesn't turn on

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

Ok, I replaced the inverter. It's still not working, but now I'm getting slightly different symptoms.

The Timer/PIC LED doesn't flash red at 6X intervals anymore. The TV turns on and stays on with a green power LED. When powered off, there's no standby LED (never was). There is still no backlight, no video and no audio.

I checked the standby power circuit at CN602 on the power board. With the power off, there's 3.36V at pin 3 (Standby), 3.36V at pin 2 (AC_OFF_DET) and 0V at pin 1 (POWER_ON). With power on there's 3.10V at pin 1 (POWER_ON).

It looks like the standby circuit is good... Where to next or do I need to replace the main board (BM4)?

[budm]

Re: Sony Bravia KDL-37M4000 doesn't turn on

So what voltages do you get now at cn 4003 in the post 13 diagram?

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

Pin 1 (Dimmer) is 0V when off and 1.63V when turned on.

Pin 2 (Backlight) is 0V when off and 3.14V when turned on.

Pin 3 (Inverter_err) is .76V when off and .93V when turned on.

[budm]

Re: Sony Bravia KDL-37M4000 doesn't turn on

It is strange that you no longer get backlights error code with the new inverter board, I have to think what to check next.
OK, try grounding the inverter error pin to ground with 100 Ohms resistor, then power up the TV to see what happen.

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

I really appreciate your assistance on this, Bud. I'll try that 100 Ohm resister later this afternoon and see what happens.

[budm]

Re: Sony Bravia KDL-37M4000 doesn't turn on

This is really interesting problem that I sure like to (need to know) also in case I run into this problem in the future, sure like to be able to solve this problem.

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

I connected the 100 Ohm resistor to pin 3 and connected the other end to chassis ground. When I plugged in the TV it read .76V and when I turned on the power it read 1.36V. Then after I turned the off the power and it dropped to .25V. I had to unplug the AC and plug it back in to get the .76V reading again.

[budm]

Re: Sony Bravia KDL-37M4000 doesn't turn on

That does not make sense for it to have that high reading of 1.36V since we basically ground the Base of the transistor to ground with 100 Ohms resistor. The Base resistor for Biasing the transistor is 10K (RB4001) so it can not have 1.36V reading due to resistor divider circuit ratio of 100: 10,000.

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

I verified the voltages and they are the same. LOL

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

I just double checked it again. Now I get 1.38V with or without the resistor when powered on.

[budm]

Re: Sony Bravia KDL-37M4000 doesn't turn on

Are you sure it is 100 Ohms resistor? To have 3.3v feeding 10,000 Ohms resistor is series with 100 Ohms to ground, and the voltage reading across 100 Ohms is 1.38V. That does not add up.

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

It's should be 1/2W 100 Ohm. Brown, Black, Brown stripes. 10 x 10^1

Let me try a different setup right quick...

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

Ok, I got rid of the jumper wires and connected the resistor directly to pin3 and pin 4 (GND) and the 1.36V drops to 0V.

[budm]

Re: Sony Bravia KDL-37M4000 doesn't turn on

And what happen when you power up the TV?
So I read the training manual again, per block diagram, that Inverter Error pin 3 should have 0 V when normal, that is why I have you ground it with 100 Ohms resistor. Since you are getting 1.3V on that pin, it means the new Inverter board is putting out an error signal. At the same time, you are not getting 6-blink error code which is confusing me now the way it is behaving with new inverter board.

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

It still doesn't do anything.

I did notice that the power LED comes on bright then dims and then is bright again while I was powering it on tonight and a few times I had to power it on/off a time or two before it would stay on.

[budm]

Re: Sony Bravia KDL-37M4000 doesn't turn on

Where did you get this replacement Inverter board from?

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

River Valley Electronics on eBay.

http://stores.ebay.com/rivervalleyelectronics

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

Now that I think about it, I did notice something odd when I was messing around with it tonight. I had unplugged the connector on the inverter to gain better access to the wires. After I plugged it back in, I was getting the .27V at power off and .93V at power on when I checked pin 3. The 1.36V didn't show up again until I turned power off and on again a couple of times while checking the voltage with and without the resistor. Those were the voltages I was reading when I first installed this new inverter.

It is weird that I'm not getting the 6X error. I suppose it could be a bad board too or something else odd is going on.

[budm]

Re: Sony Bravia KDL-37M4000 doesn't turn on

That should have cause 6-blink error, that is why I am so confused right now since the main board is receiving and error signal so it should be blinking right now. What happen if you put the old board back in?

[winterwar]

Re: Sony Bravia KDL-37M4000 doesn't turn on

I was thinking about doing that to see what happens. I'll swap them out in the morning and let you know the result.