Sony 46EX400 won't turn on, 2 blinks

[tibimakai]

I have picked up this TV and I couldn't find anything about this issue.
It turns on for like two seconds with nothing on the screen(no BL), just the red LED and then begins blinking the error 2.
This error points to the main power supply.
I have measured all the pins at the PS and to me the only fishy voltage is the BL_ERR and the T-Con is not getting the needed voltage.
here are the voltages:
CN6150 connector:
T-CON_ON= -0.004v
T-CON_VCC= 0.092V
DIMMER= 2.96V
BL_ON= 0.046V
BL_ERR= 3.32V(TV ON OR OFF)
REG 12V= 12.71V
AUDIO 12V= 12.72V
POWER ON= 3.3V
AC_OFF_DET= 2.75V
STBY= 3.32V

Main caps= 396V

CN6702 connector:
12V= 12.67V
FB= -.0001V
GND= 0V
LO= 12.02V

Capacitors are KMG, KMZ. I don't see any bulging.

These voltages are there only for those two seconds and then they are gone, except the STBY and the BL_ERR.

T-con fuse is OK.
Inverter transformers show 139-142 Ohm.
Checked for shorted FETs or diodes, couldn't find any.
No visible damage.
Here are some general view pictures. If specific areas needed, just ask.
I would appreciate any input.
If I fix it, I may keep this one and sell my 46" Samsung.

[DaveHignett]

Re: Sony 46EX400 won't turn on, 2 blinks

Hi!

Firstly, I've never had one of these sets on my bench, but I'll do my best with some pointers if I can.

The T-CON voltage does seem very low. Have you taken these measurements with the ribbon disconnected, ie; with the PSU running open, or did it have the loads connected to it?

If it's open when you've measure the O/P, then I'd be looking at caps on the PSU board. I'm sure you already know that just because they're not bulged, it doesn't mean they're operating as they should.

If, on the other hand, the PSU had a load connected to it when you took the measurements, I'd be opening the T-CON supply cable and trying to measure the current, or disconnect it to see if the voltage rises to somewhere near normal. If it does, then something's shorted, or nearly shorted, on the T-CON board.

There will be some form of feedback system from the various boards back to the PSU, maybe opto-isolators etc, which will shut down the PSU if any of them detect a fault. I suspect this is what's happening, as it's firing up initially then shutting down.

In the first instance, i'd try to disconnect PSU, power up and get the T-CON
voltage. If this is fine, then reconnect and it'll probably fall. If this happens, then it's time to have the T-CON board on the bench for some surgery!

Hope this helps!

Dave

[DaveHignett]

Re: Sony 46EX400 won't turn on, 2 blinks

I've just checked and we've got a service manual for this set if it helps? If you need it, email me on djhignett@live.co.uk and I'll email it back to you.

Dave

[budm]

Re: Sony 46EX400 won't turn on, 2 blinks

"CN6150 connector:
T-CON_ON= -0.004v
T-CON_VCC= 0.092V
DIMMER= 2.96V
BL_ON= 0.046V"
The reason that there is no T-CON VCC is because the T-CON on signal is stuck LO, the signal is used to turn on the switched transistor to supply 12v to the T-CON (see page 21 of the service manual).
The BL_ON is also stuck LO.
The BL_ERR (FB) is LO when it is normal, this TV uses Balancer board which has a bunch of the current sensing transformer on each lamp, the when the lamp draws too much current, it will send out the signal to turn off the lamp.
http://s807.photobucket.com/albums/y...psa9c38f7d.jpg
See https://www.youtube.com/watch?v=oE6K4xBVweA
Notes: Samsung/Sony basically uses the same setup for the Balancer board.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

Thank you all for your suggestions.
Bud I will check out those voltages. I have seen that video, but I didn't think that my issue could be the same as in that video, but it makes the most sense.
I will ask you for the service manual also. Thank you for the suggestions and offer.
Everything was measured with all connectors connected.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

I havedone some measurements, but I haven't found anything that out of order then in that video.
Number 1 from the top of the TV, had the highest voltage. Most of them were under 2mV AC, one it was just a bit over 2mV and the first one from the top of the TV went up to 6.7mV.
Removed the transformer, checked out OK and then I have soldered a jumper as in that video.
The TV didn't turned on. It was in the same situation with the two blinks.
I have noticed some differences between the last transformer/diode measurement and the rest of the transformer and diode measurements.
Firstly the diode next to the first transformer shows .608 on the diode check scale, on the side closest to the "bad" transformer(w/transformer removed) the other side of the diode shows .554.
Measurements between these points (yellow line and red line in the picture) on the yellow line has different value then between the same points on other transformers.Forgot to wriyte it down,but it was something around 330 Ohm or Kohm.
I will update with more info as I'll check more.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

It doesn't seem that this method works.
The voltage measured it's much higher with the jumper, then with the transformer.
Should I take the panel apart and check out the tubes themselves?

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

Any more ideas?

[budm]

Re: Sony 46EX400 won't turn on, 2 blinks

Did you get the service manual yet? we need to find out what the BL_ERR signal is, if LO = NORMAL, or HI = NORMAL.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

It's in the first post, but it's pretty basic.
I'm thinking hat maybe I should remove two transformers, to see how they are connected the pins between each other. What do you think?

[budm]

Re: Sony 46EX400 won't turn on, 2 blinks

i saw that one but I thought Dave also has the service manual that he offers. I am still thinking the problem is on the power supply board.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

Good call, I have completely forgot about asking for it, stupid of me.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

I have just sent the E-mail.

[budm]

Re: Sony 46EX400 won't turn on, 2 blinks

We can try to see if the high voltage transformer even try to fire up when the TV is first powered up. You can solder a piece of wire to the bottom of the CFL, then just touch that pin the one of the pad in red circle, you should see the lamp flash if the high voltage does come on for second when you turn on the TV. You can try that on the monitor.
I think the High voltage transformer is not being driven by the MOSFETS.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

I have extra ccfl tubes, should I used one of them instead, or it's better the bulb?

[budm]

Re: Sony 46EX400 won't turn on, 2 blinks

You can use that too, just need to make contact with just one end of the test lamp, just have o hold the lamp body with your hand.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

I will try it out when I get home.

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

Nothing happens Bud.

[budm]

Re: Sony 46EX400 won't turn on, 2 blinks

We need to look at the circuits around the high voltage transformer. There are 4 devices mounted on the heatsink next to the transformer, they should be the driver for that transformer, check and see if the b+ from the large dc filter is connected through some kind of fusible resistor. What voltage do you have on that large cap?

[tibimakai]

Re: Sony 46EX400 won't turn on, 2 blinks

396V, but only for that second or two. I have to check on the resistor though.