Sony Bravia no picture but backlight on

[capxrf]

Re: Sony Bravia no picture but backlight on

Holy crap!! Really!?

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

I order my t-con today.
I got it from Mat Electronics for $9.95!!

[capxrf]

Re: Sony Bravia no picture but backlight on

My board is still on its way. It should be here tonight or tomorrow. I'm pretty anxious. I really hope it fixes it after all this time. I got mine from Discount-Merchants for about $50 (again, I was the one with the Original tv in this post, a 32" Bravia)

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

so, I've gone as far as my limited knowledge permits me...
I will be ordering the t-con online. However, there is a minimum quantity order, so I will need to purchase more than one item. What other boards are known to fail on this tv? I'll order that board too!

[PlainBill]

Re: Sony Bravia no picture but backlight on

So, I replaced the fuse and started testing smds again but the meter still isn't reacting when I touch the ends to the smds. Am I doing something wrong?
Please see pics below of the meter when the ends are not touching, when the ends are touching and when I try to test two smds.
Maybe the meter is faulty? I have another meter but doesn't have a setting at 200...

To mangle Wm Shakespeare '“The fault .... lies not in our meters but in ourselves.”
Follow this logic.

The T-Con board gets it's power through that fuse.
It converts the power to drive the LCD display, as well as using some for itself.
One thing that can go wrong is a SMD cap shorts, loading the power line, and blowing the fuse.
Per Wizard, when that happens the cap will have a reading below 80 ohms.
You do not find a cap with a reading below 80 ohms.
Conclusion: None of the SMD caps are shorted. (Just for luck check ALL SMD caps)

Other possible causes of this problem is a fault in one of the ICs, a fault in the voltage converter, a bad inductor, a fault in the LCD panel. One thing that helps troubleshooting this is the total current through the fuse is only a little over 3A.

PlainBill

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

So, I replaced the fuse and started testing smds again but the meter still isn't reacting when I touch the ends to the smds. Am I doing something wrong?
Please see pics below of the meter when the ends are not touching, when the ends are touching and when I try to test two smds.
Maybe the meter is faulty? I have another meter but doesn't have a setting at 200...

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

let me clarify, first I'm changing the fuse in order to start testing the ceramic smds again. For now ALL the smds do not cause the meter to react in any way. When I turn on the meter and set it on 200, it displays 1.
This reading doesn't change at all when I touch any smd. However, when I touch the two ends together, it give me a 0.4reading.
So I'm hoping that by first changing the fuse and then doing the readings, it might change something.
BUT I WILL NOT ATTEMPT TO PLUG THE BOARD BACK ON THE TV UNTIL I"VE FOUND THE CULPRIT

[PlainBill]

Re: Sony Bravia no picture but backlight on

DO NOT add another fuse! Find the short FIRST!

Repeatedly blowing fuses could harm the system as the system will be repeatedly subject to overload.

If it reads 1.0 on the 200 ohm scale....are you sure thats not OL or something?

1.0 on my meter means 1.0 ohms....and if you get that on an MLCC cap, its dead.

You are definitely right about simply replacing the fuse. It's blowing for a reason. As far as the resistance, take a look at the picture of the meter. It's on the resistance scale, the leads are not shorted and it's displaying 1 . (First digit 1, three spaces, then the decimal point).

PlainBill

[hardwareguy]

Re: Sony Bravia no picture but backlight on

DO NOT add another fuse! Find the short FIRST!

Repeatedly blowing fuses could harm the system as the system will be repeatedly subject to overload.

If it reads 1.0 on the 200 ohm scale....are you sure thats not OL or something?

1.0 on my meter means 1.0 ohms....and if you get that on an MLCC cap, its dead.

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

That means it is reading more than 200 ohms. 200 ohms is greater than the 80 ohms Wizard mentioned. This means the cap isn't shorted. This is good news, you have eliminated the caps as a possible problem.

And I notice you STILL haven't answered the question - what was the rating of the replacement fuse?

I'm not trying to dump on you, but it's obvious you don't have a strong electronics background. I'm trying to make sure the simple things are correct.

PlainBill

The original is a 3A. The replacement was also 3A, but that burnt.
I'm going to change the fuse again and will then start testing the smd's again as hardwareguy suggested.

[Wizard]

Re: Sony Bravia no picture but backlight on

Yes, 3A fuse.

Looks like you have a problem deeper than that, 2A is too small fuse and I have seen some that draw high current than 2A The marking says 3A and you have to use 3A fuse. Even my 32" panel 5V supply specifies 2.5A fuse for max of start up 1.9A, running 1.4A.

Cheers, Wizard

[PlainBill]

Re: Sony Bravia no picture but backlight on

Problem is that nothing happens when I have it on the setting you specified. It stays locked on 1.0

That means it is reading more than 200 ohms. 200 ohms is greater than the 80 ohms Wizard mentioned. This means the cap isn't shorted. This is good news, you have eliminated the caps as a possible problem.

And I notice you STILL haven't answered the question - what was the rating of the replacement fuse?

I'm not trying to dump on you, but it's obvious you don't have a strong electronics background. I'm trying to make sure the simple things are correct.

PlainBill

[hardwareguy]

Re: Sony Bravia no picture but backlight on

Wow nice TV....don't give up on it! I have a KDL46XBR2 and love it. I would replace every board in the set if need be to fix mine!

Comparable sets today still cost over $1500.

Check that the Tcon board fuse is the same as the original and put your meter on the 200 ohm scale. Place the leads together on the meter and see what indication it gives you when shorted, it should say 0 ohms or very close to 0 (0.01 or so).

Being familiar with your instrument is vital to your success and safety.

WARNING! NEVER attempt to measure resistance of a live circuit as this will cause a short circuit. You could easily destroy the meter and the circuit you are testing. If the available current is large enough, you could be badly burned. At the very least you'll blow the meter fuse.

DANGER! A meter with a blown fuse may give no indication that it is not working properly. Always test the meter before using it. Touch the meter leads together and make sure the meter reads 0 ohms before using it. If the fuse is blown it will continue to read OL or infinity. This false reading could cause you to assume a live circuit is dead, with consequences that could be fatal!

Follow Wizard's advice...he is THE MAN when it comes to TVs.

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

Well, you may be feeling the wrong thing. You have the meter on the 200K range. You should have it on the 200 ohm range.

PlainBill

Problem is that nothing happens when I have it on the setting you specified. It stays locked on 1.0

[PlainBill]

Re: Sony Bravia no picture but backlight on

Hi Fellas,

So I borrowed a meter (see picture for the setting I used)
Tested all large and medium ceramic smd. See picture for all measurements.
The ones labelled a through L all measure in excess of 160, except for b (77.8), c (78.1) and L (59.2).
From M through U all seem to be either 4.5 or 2.7, or 2.8.

I feel it, we're close now!!

Well, you may be feeling the wrong thing. You have the meter on the 200K range. You should have it on the 200 ohm range.

PlainBill

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

Hi Fellas,

So I borrowed a meter (see picture for the setting I used)
Tested all large and medium ceramic smd. See picture for all measurements.
The ones labelled a through L all measure in excess of 160, except for b (77.8), c (78.1) and L (59.2).
From M through U all seem to be either 4.5 or 2.7, or 2.8.

I feel it, we're close now!!

[Wizard]

Re: Sony Bravia no picture but backlight on

unplugged from power for safety sakes!

Yes all these medium to big ones brown-purplish look blocks on T-CON. Rest of other boards don't worry about those yet.

Cheers, Wizard

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

newbie question here, but does the power need to be on in order to measure ohms? Am i looking at the ceramic smds only on the t-con board or on all other boards too??

[Wizard]

Re: Sony Bravia no picture but backlight on

3A

And I think you have a bad ceramic SMD on voltage supply somewhere. Start measuring with your ohm-meter and try to find one that is below 80 ohms.

These MLCC big capacitors SMD that is very high density tend to fail by shorting.

Cheers, Wizard

[bobbyvalentino1978]

Re: Sony Bravia no picture but backlight on

the original fuse was a LF3A...
Wizard, what do you think of Plainbill's feedback?