Big Black Bravia

[momaka]

Re: Big Black Bravia

I can try to know if the led that lites is the POWER/RESERVE_LED or the stby one. Ideally pin 24 (key) drives pin 67 (power) and the main processor is very ill.

Or maybe one of the many ICs isn't getting proper power, and this is causing the main processor to not start.
With that said, I think it's time to do some really hard work now... on the schematics for each board, mark every pin of every IC that has standby power coming to it. Then make a list of those ICs and the pins they should have standby power on. After that, take your multimeter and verify that each IC in your list does indeed have standby power going to it. Check off items as you go down through the list so you know what you've checked and what's working.

Also, I'm not sure if you have noticed, but any components on the schematics marked with "XX" underneath means they were not installed on your TV. Just keep that in mind as you follow the schematics.

[Longbolt]

Re: Big Black Bravia

Thanks, this is a good idea I will do that next week end. Just don't know how many of them I can check, there are IC's on both sides.

[Longbolt]

Re: Big Black Bravia

Now I have checked all the IC's on both sides of the BE and A2E4 boards that should have Stby power on.
Many of them have the proper Stby voltage.

Here is the list of the IC's that I “suspect”


BE BOARD:
IC 1003 (main processor)
Pin 41 – 0V normally 3.3V
Pin 45 – 0V normally 3.3V
Pin 49 – 0V normally 3.3V
Pin 12 – 1.86V normally 3.3V
Pin 62 – 1.13V normally 3.3V
Pin 67 – 0V (I can't locate the resistor that connects this pin to the 3.3V)

IC 7402 (PORT EXPANDER)
Pin 1 – 3.26V normally 5V
Pin 2 – 2.7V normally 5V
Pin 9 ok – 5V
Pin 10 – 0.02V normally 5V
Pin 16 ok – 5V


A2E4 BOARD:
PORT EXPANDERS
IC 8500
All pins connected to 5V
Pin 1 – 0.05V
Pin 9 – 4.57V
Pin 10 – 1.89V
Pin 11 – 5V
Pin 13 – 5V
Pin 16 – 5V

IC 8503
All pins connected to 5V
Pin 1 – 4.57V
Pin 2 – 0V
Pin 9 – 0.02V
Pin 10 – 5V
Pin 11 – 5V
Pin 12 – 5V
Pin 16 – 5V

I haven't checked the IC's on GE2 and G3 because I have the 5V Stby which goes directly from G3 to A2E4.
I slightly suspect the BE board.
And yes, it's a hard job! And not for beginners like me. In the beginning I hoped to find a blown fuse, broken tube, exploded cap…
Just wonder how many people have been working on that schematic to make it

[momaka]

Re: Big Black Bravia

>> IC1003
>> Pin 41 – 0V normally 3.3V
>> Pin 45 – 0V normally 3.3V
I think those readings are fine. Note that resistors R7543 and R7544 are indicated with "XX" on the schematic - meaning they shouldn't be installed on your TV. Check your board, though.
In any case, these are signal pins, so the IC may be pulling them low intentionally. Therefore, you don't know whether they should have 3.3v or not (unless IC1003's data sheets specifies it should).

>> Pin 49 – 0V normally 3.3V
Not sure about this one. Resistor R7592 should be installed while R7593 isn't. But again, this being a signal pin, you don't know whether it should or shouldn't have 3.3v.

>> Pin 12 – 1.86V normally 3.3V
>> Pin 62 – 1.13V normally 3.3V
Same problem as Pins 41, and 45. R7551 and R7548 shouldn't be installed. Or are they?

>> Pin 67 – 0V (I can’t locate the resistor that connects this pin to the 3.3V)
Check the empty resistor spots. Schematic says it should be installed.

If any of the above resistors are installed when they shouldn't be or vice versa, this will definitely complicate the analysis. Therefore, I think you should just check only standby power pins on IC1003, namely:
Pin 6 (2.5v), Pin 8 (3.3v), Pin 22 (2.5v), Pin 40 (3.3v), Pin 56 (2.5v), Pin 73 (2.5v), Pin 75 (3.3v)
Do you have power on all of those?

>> IC 7402 (PORT EXPANDER)
>> Pin 1 – 3.26V normally 5V
>> Pin 2 – 2.7V normally 5V
Resistors R7579 and R7580 may not be installed on your TV.

>> Pin 9 ok – 5V
>> Pin 16 ok – 5V
Looks good there.

>> Pin 10 – 0.02V normally 5V
Can't comment on this one

>> A2E4 BOARD:
>> PORT EXPANDERS
>> IC 8500
...
>> IC 8503
I'm not sure, but it's possible that these voltages may be fine.

And yes, it’s a hard job! And not for beginners like me. In the beginning I hoped to find a blown fuse, broken tube, exploded cap…

I don't think you're a beginner at all. Most people would just pick a board (either BE or A2E4) buy a new one, swap it, and hope it works. You did quite a bit more than that and I do believe you when you say it was a lot of work. It sure would have been nice if this was a simple problem, though.

[Longbolt]

Re: Big Black Bravia

Most people would just pick a board (either BE or A2E4) buy a new one, swap it, and hope it works.

Nice of you to say that, I sometime wonder if a human being can replace one those components especially if they have more than two legs and is probably cheaper to buy a board than a iron for soldering and desoldering those SMT's .

I think you should just check only standby power pins on IC1003, namely:
Pin 6 (2.5v), Pin 8 (3.3v), Pin 22 (2.5v), Pin 40 (3.3v), Pin 56 (2.5v), Pin 73 (2.5v), Pin 75 (3.3v)
Do you have power on all of those?

Yes I do have them all right.

I finally found that resistor to pin 67 and I have 3.3V before it, so the processor is pulling it down. So when I pres power ON something is preventing it to go high.
I have 2.5V on the key connector. I don' know also what AC OFF DET means (which is high on G3 1.35V on STBY mode)
I have 2.95V on the collector of Q7419.

Anyway I am grateful to you for your help momaka, I would feel very stupid on my own in front of that .PDF

To give you better idea of my level I joined the following circuit witch I do not really understand!

I build it some time ago and it works. But I build it with a involuntary mistake (normally the emitter of a PNP transistor is connected to positive) in my case I connected PNP emitter to ground, only like this the circuit is working.
When I saw that it was working with a mistake, refusing to work “normally”, I stopped to try and to want to understand. Even though there was no confusion with collector emitter, I still do not understand the way the cap is charged (why + to ground) and where pnp base current goes, to cap? Just knew that R 4.7M regulates freq. and R680 ohm regulates pulse width.

With all this said some may smile thinking haw can I expect to mend all that mess.
Once I heard; “I have done so much, with so little, for so long, I can accomplish almost anything with nothing”. Some may smile again
The second picture shows a ferrite core memory found in older computers, I thing it illustrates well the sentence above.

So I have little hope left !i

[tom66]

Re: Big Black Bravia

AC OFF DET probably goes low when the power plug is pulled. It gives the TV time to stop writing to the EEPROM and turn the audio off to prevent the popping sound (some amplifiers have built in anti-pop/click circuit) before the power supply completely fails. I think it should be higher than what you are reading...

[Longbolt]

Re: Big Black Bravia

AC OFF DET probably goes low when the power plug is pulled. It gives the TV time to stop writing to the EEPROM and turn the audio off to prevent the popping sound (some amplifiers have built in anti-pop/click circuit) before the power supply completely fails. I think it should be higher than what you are reading...

You should be right! Welcome.
AC off det has a lot to do with audio circuits but also with Backlight. I remember when I was forcing PSU to run and unplugging from wall I was hearing speaker noise after some seconds.
AC OFF DET comes from 5Vstby trough 22K resistor. A photo-coupler on the PSU board is charged to ground that signal.
If the readings I have are not good it will probably mess with the Backlight also.

[tom66]

Re: Big Black Bravia

You should be right! Welcome.
AC off det has a lot to do with audio circuits but also with Backlight. I remember when I was forcing PSU to run and unplugging from wall I was hearing speaker noise after some seconds.
AC OFF DET comes from 5Vstby trough 22K resistor. A photo-coupler on the PSU board is charged to ground that signal.
If the readings I have are not good it will probably mess with the Backlight also.

Try pulling it using a 1k resistor to 5Vstby (should override the optocoupler.) Also try grounding it. If either turn the TV on you have found your problem.

[Longbolt]

Re: Big Black Bravia

Try pulling it using a 1k resistor to 5Vstby (should override the optocoupler.) Also try grounding it. If either turn the TV on you have found your problem.

When you look at Q8601 and the zener diodes connected to Backlight. Should AC OFF DET be high or low on stby mode?

[Longbolt]

Re: Big Black Bravia

I have tried to pull it down but not up. I'm temped to try the 1K resistor pull up but since I'm not knowing what I'm doing I'm scared to kill something.
I tried to check the phfotocoupler on it's transistor side; diode test, when connector is unplugged it does not conducts collector-emitter, emitter-collector. Not shorted anyway, I assume it's OK.
When connector (on/off) to the main board is plugged diode test on the photocoupler terminals it conducts just one way.?!

[tom66]

Re: Big Black Bravia

I have tried to pull it down but not up. I'm temped to try the 1K resistor pull up but since I'm not knowing what I'm doing I'm scared to kill something.
I tried to check the phfotocoupler on it's transistor side; diode test, when connector is unplugged it does not conducts collector-emitter, emitter-collector. Not shorted anyway, I assume it's OK.
When connector (on/off) to the main board is plugged diode test on the photocoupler terminals it conducts just one way.?!

A 10k resistor will limit current even further, but it's possible the impedance of that pin is low, in which case it wouldn't provide enough drive. 1k across 5V is 5mA, unlikely to cause any damage.

What numbers are there on the PSU board? It might be possible to get a new PSU for around $50. Given the TV was free, it might be worth it, instead of chasing hundreds of small problems.

[Longbolt]

Re: Big Black Bravia

What numbers are there on the PSU board? It might be possible to get a new PSU for around $50. Given the TV was free, it might be worth it, instead of chasing hundreds of small problems.

Buying and throwing, the logic gates of modern life!!

You have said clever things about AC OFF DET and how it works, but I do not understand what's make you think the PSU is bad.

Poker or crossword?

[momaka]

Re: Big Black Bravia

When you look at Q8601 and the zener diodes connected to Backlight. Should AC OFF DET be high or low on stby mode?

I *think* it should be low. When it's high, this will make the base-emitter junction of Q8601 forward biased, thus pulling BACKLIGHT low. Most monitors also have a pin called BACKLIGHT or BL. If I remember correctly, this pin usually goes low when the monitor is on.

If this is the case here with this TV, then AC OFF DET should be high. Otherwise it should be low.

As a last resort, you can always try to jumper the PSU ON by pulling POWER ON high, then pull PSW DIG, PSW SW, and PSW PANEL 5v high (this will enable the GE2 to produce all of the voltages for the TV. Probably won't work since

Buying and throwing, the logic gates of modern life!!

Very true. Actually, that's rather sad than funny.

[tom66]

Re: Big Black Bravia

Buying and throwing, the logic gates of modern life!!

You have said clever things about AC OFF DET and how it works, but I do not understand what’s make you think the PSU is bad.

Poker or crossword?

It depends what your time is worth. I wouldn't spend any more than a few days trying to debug a problem unless I realllly wanted to. I'd buy a new power supply and install it.

I think the AC OFF DET should be either 0V or 3-5V but not 1.35V. Whatever numbers on your board could help in tracking down a service manual.

[Longbolt]

Re: Big Black Bravia

I agree with you, Tom66, it's time consuming!
For me this is an educational and experimental device, only because I was able to find the service manual and I believe in miracles.
It may become a TV again, one day, if I do the right bid.
I was unable to aloud so many pixels to go to the trash just because of something… very small. (and that's the problem)
I already have a TV that I almost never watch.
I use this think instead: http://www.youtube.com/watch?v=y-jOc...eature=related

I have tried to pull AC OFF DET up and down with the 1K R but no success.
Then I have tried to ensure that PSU STBY Power will have enough power to feed the circuits by connecting external power supply parallel to the stby 5V.
-NO change. AC OFF DET goes from 1.35 to 1.38V
As soon I force PSU to start by connecting STBY and POWER ON trough 1K resistor AC OFF DET goes LO.
When I pull up PSW DIG, PSW SW, and PSW PANEL trough 1K R I have all the regulated voltages from GE2 regulator board
I even wake up the inverter and beautiful backlight came. But Frankenstein is still sleeping.

1.35V is not very clear voltage but it comes from 5V rail through 22Kohm resistor and it goes to many transistor bases.
5V / 22000ohm = 0.002A ?
With 1K R connected to 5stby I have 4.21V on AC OFF DET
And if it is not a good reading, then something sucks too much. When there is no connector connected I have 5V.

I'm tempted to cut that wire. !


The good news is that my sister called me yesterday an said “ I found a flat TV set by the trash on my street and picked it up for you if you want to mend it”
So the next Zombie is waiting in her cave!

Any ideas about the flasher circuit at post 25?

[tom66]

Re: Big Black Bravia

http://blog.coppelltvrepair.com/2010...m-dead-no.html

Looks similar to your problem.