Toshiba 37AV600T - not powering on

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

some nichicon, other brown ones without a name..

[tom66]

Re: Toshiba 37AV600T - not powering on

This TV might use a buck converter to generate the 12V from the 24V or 18V line. As it only uses one transformer it's very unlikely one output could fail with the others good. I see at least one buck converter on there. The 18V is likely for the audio amplifier.

Also, what is with the LVDS connector on the main board? Looks like it is lifted up a little?

Brown caps with a crown symbol like this are United/Nippon Chemicon. http://media.digikey.com/Photos/Unit...E10-SERIES.jpg

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

the LVDS connector is lifted because i took some of the photos after taking apart the connectors..
about the 12v, there are 3 12v lines that supply constant voltage from PS to the main board. on the other hand the 12VLCD lines are always 0v.

[tom66]

Re: Toshiba 37AV600T - not powering on

The 12VLCD may be the fault then. Can you get a picture of the reverse (green side) of the power supply?

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

there is a pic of it on the previous page.. if you need to zoom on some area please let me know.

[tom66]

Re: Toshiba 37AV600T - not powering on

OK, didn't notice that, thanks.
Can you highlight the 12VLCD pin(s) on here so I can trace it through:
https://www.badcaps.net/forum/attach...6&d=1357033909

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

here it is..
many thanks for the assistance!

[tom66]

Re: Toshiba 37AV600T - not powering on

OK, see the attached image.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

hey,
diode- seems OK, using multimeter in diode test mode, in circuit - 0.174v forward voltage and closed under reverse voltage.
yellow thing - indeed appears shorted.
IC - 8105QL , this one i think:
http://pdf1.alldatasheet.com/datashe...SI-8105QL.html

[tom66]

Re: Toshiba 37AV600T - not powering on

OK, regarding the IC, is it possible to check the voltage on pin #2 (VIN.) It should be the same as pin #10 of P811A. Which voltage should that be (I understand you have a legend somewhere for the pins?)

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

hi,
i tested voltage on pin #2 - Vin. it is actualy the same as pin #11 (not 10)
of P811A. this pin is marked NC and the voltage there is 24v which appears when the TV tries to start.
by the way pin #10 is GND.
Edit: i didn't get any voltage reading on any other pins on that IC except for the Vin.

[tom66]

Re: Toshiba 37AV600T - not powering on

Must have miscounted them. So the IC has input voltage.

What does pin #3 measure? This is a high frequency switching output, but should *approximately* measure 12V on a DMM,

What does pin #7 measure? It should measure >2.8V to turn the IC on.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

Hi,
actually there is no voltage at all at pins #3 or #7.. weird

[tom66]

Re: Toshiba 37AV600T - not powering on

Well, since pin #7 is low, the IC will not work, because it is being told to turn off.

So I'd look more towards why the other power on signals aren't present. Have you forced on ALL of the power signals?

And what is the name of the marked pin in this image?

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

The pin you marked is PWR_LCD and is dead. i see now that this pin is connected to pin #7 through a 220 ohm resistor. guess that's why the IC doesn't start.
at this moment i don't force any power on signals, just measuring "as is".
Just checked that PWR_LCD signal is coming directly from processor.. so the processor doesn't send PWR_LCD signal for some reason...

[tom66]

Re: Toshiba 37AV600T - not powering on

So, this must be the problem, it is with the processor :/ or some other part of the main board.

What is the part number on the main board. It may be cheap enough to replace.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

the main board part number is PE0736..
also there is V28A000980A1 written.
when the tv tries to start, i hear high pitch noise from the coil (the one with blue circle and 100 written on it) i marked in the image.. when i press down on it with my finger it fades. can it be something meaningful ?

again.. great appreciation for you trying to help me

[tom66]

Re: Toshiba 37AV600T - not powering on

Someone has the board for $49 + $24 shipping; maybe you can negotiate it down.
http://www.ebay.com/itm/BRAND-NEW-TO...-/170908118555

Some test points in the image below to check.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

3.3v is availible on the smd cap right next to the 3.3v text point.
can't find voltages on any other test points or anywhere near them. actualy they all seem to be in continuity with GND when the board is unplugged.
another thing - those inductors with 100 printed on them, the one that i circled does get 1.8v when tv tries to power up, but his twin on the left doesn't show any voltage at all. this 1.8v sound like power to the processor.. no?
BTW the board on ebay looks very refurbished.. caps are changed (original are blue) and what is that jumper going along all the board ?!

[tom66]

Re: Toshiba 37AV600T - not powering on

The brown caps are likely originals before Toshiba started using cheaper caps on the main board. They are under less stress so it's usually OK. The wire might be a factory mod to fix a fault.

The other voltages might not be present in standby.
The CPU runs off +1.05V_D, I think...