Sony Bravia KDL-37M4000 doesn't turn on

[winterwar]

I was given a Sony Bravia KDL-37M4000 that doesn't turn on. The previous owner sais it was working fine but when she turned it on a few days ago "and pfffffffffffffffffffffffffth ... yeah, that's what it sounded like ... an electrical fizzing, ear splitting sound when the damn thing blew." Her words exactly. LOL

After I got it home, I plugged it in to see what it was doing. When I hit the power button the green power LED comes on for a few seconds and I hear a relay click, then it shuts off. The Timer/PIC LED will then begin flashing continuously, 6 times, pause, 6 times, etc. I took the back cover off to see if there was anything obvious like bulging capacitors, but didn't see anything.

The TV was manufactured in 2008. Any ideas as to what the problem might be?

[tom66]

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

Smell anything burnt, see anything gone bad, heat/burn marks etc?
Pictures of the boards?

[budm]

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

Service manual:
http://elektrotanya.com/?q=showresul...oria=&kat2=all

[winterwar]

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

There's no damage anywhere that I can see. All the caps look good and aren't bulging or exploded. No burnt smell anywhere and nothing looks burnt. There are a couple of spots on the back of the inverter that look like they got a little warm.

I'm looking over the links you posted, budm.

Overall:



Power Board:





Inverter:





BM Board:



TCON:

[jose6326]

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

I had a similar problem on the sony bravia I am working on now
Apart from the sound effects you described it made

My needs a main board

Try disconnecting one of the connectors from the main board then power it back on

See if you get the backlight on
If you dont, disconnect power wait a few minutes for caps to discharge reconnect then disconnect another connector on main board and connect power again

If you get the backlight working then you need a mainboard which is how I figured it by out the service manual bud provided

Thanks again bud

[winterwar]

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

I tried your suggestion, jose6326. Couldn't get a backlight to come on with any of the connectors removed.

The service manual says the Timer/PIC LED flashing 6 times is a backlight problem. It could be caused by the BM4 Main Board, G2D Power Board, Inverter or LCD Panel. That narrows it down some. ;-)

[tom66]

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

Do you have a digital multimeter?

[winterwar]

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

Yes, I do have a digital multimeter.

[tom66]

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

OK, can you see a place to check the 24V at the inverter connectors? You can check for 24V at the inverter or power supply.

[winterwar]

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

Let me check ... Alright, I'm getting 24.28V at each of the pins on the inverter connector on the power supply.

[budm]

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

Can we get good clear focus picture of the inverter board, and any labeling by the connector? We need to look for BL_ON ot INV_ON signal pin.

[winterwar]

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

No labels on the connector to the inverter (CN1) and didn't spot anything labeled BL_ON or INV_ON. Unfortunately, the service manual doesn't give any diagnostic information and only has schematics for the mainboard and power supply.

Here are some better closeup pics:

[winterwar]

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

The last 4 pins on the 14 pin connector to the inverter go to a 5 pin connector on the main board. The other 10 pins go to the power supply.

On the mainboard connector, pins 2, 3 & 4 are the black wires. Pin 1 is white. There is no connection on pin 5.

BM4 5 pin connector schematic:

[budm]

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

OK, check pin 2 (BACKLIGHT), that is the BL_ON signal to turn on the inverter.
Also check pin3 (error) when TV is off and when you turn it on.

[winterwar]

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

Pin 3 is .76V when off and 1.9V when turned on. After about 5 or 6 seconds the TV shuts itself off and the red LED starts flashing. Then it only reads .27V.

Pin 2 is 0V when off and 3.2V when turned on. After a few seconds and BEFORE the TV shuts itself off, it drops to 0V.

[budm]

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

OK, I need to find out what Inverter error (Pin3) and the Balancer (pin5) error signal should be HI or LO for normal operation.

[winterwar]

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

There's no connection on Pin 5. The plug has an empty hole.

[budm]

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

OK, the Inverter error should normally be low when the inverter board is OK.
Per training manual, the 6-blink code will only happen if the inverter board is not working, poor lamp connection will not cause 6-blink code.

[winterwar]

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

I'm getting 24V on Pin 1 at the inverter connection (CN1). I'm also getting 3.2V for Backlight_ON voltage at Pin 2 on the BM board connector (CN4003), but it drops to zero after about 3-4 seconds. Should that be a continuous 3.2V or is it just a momentary signal to power on the inverter?

I don't get any voltage readings on the HV side of the inverter when I turn on the TV per the instructions on FIG 4-4 that you provided.

[winterwar]

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

I have another inverter board coming. Hopefully, that will solve the problem. The inverter that's in there has a couple of dark spots on the back that look suspicious.