Toshiba 37AV600T - not powering on

[carbonfiber]

Hello,
hope someone can guide me to find what is going on,
PS model : SRV2169WW
Main Board : PE0736
Got the TV in that state: the tv won't power on, RED led indicator lights when plugged into main. when power button pressed i hear some high pitch noises from PS and main, after a few second RED led turn off and after another couple of seconds lights RED again. There is no picture nor backlight nor nothing.
reading i've done so far on pins that go from PS to main:
12v - present on standby and power on.
5v - present on standby and power on.
PWRDB - dead.
PWRTV - 0v on stdby, 3v when power button pressed.
PWR_PROTECT - 2.9v constant.
PWR_SIG - dead.
AC_DET - 0v on stdby, 3.9v when power button pressed.
PWR_LCD - dead.
two 12VLCD pins - dead.
24v to inverter (?) - dead.
18V - present on power on.
tried to short 5v to pwr_sig - same thing only this time speakers make weird noise and 24v appears temporarily on outputs to inverter .
would appreciate any ideas ( or schematics ), Thanks!

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

Someone knows what is the value of AC_DET and other signals expected for normal operation ?
Thanks..

[tom66]

Re: Toshiba 37AV600T - not powering on

I will attempt to find the service manual and upload it.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

I will attempt to find the service manual and upload it.

Thank you

[tom66]

Re: Toshiba 37AV600T - not powering on

Unfortunately... no luck!

I have worked on the 32WLT66S which had a similar "not powering on" fault, but that is a UK model, I am not sure if it is similar to this model.

Can you post some pictures of the TV's boards, and one of the overall layout? Please use the manage attachments function.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

Hi Tom,
Thanks for the reply!
i took some photos as you suggested.
I would like to investigate the following IC's on the PS (marked them in red square) :
ssc9500-16 pin IC
mip2f2 - 7 pin IC
do you know how to check those for correct functioning? Any other tests i can do?
Thank you and Happy new year all

[tom66]

Re: Toshiba 37AV600T - not powering on

Unfortunately the 32WLT66S is completely different! Mine had about 8 individual boards, but yours has only an AV, PSU, T-con and probably an inverter.

While you may not know what AC detect should be you could cut the wire going to the main board and feed your own voltage in.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

Hi,
Just did that, cut the AC_DETECT wire. normally (with AC_DETECT connected to PS = 3.94v) the TV would make two attempts of starting (red led turns off, no greed light) and then return to STDBY mode (red led turn back on).
if i jumper AC_DETECT to PWRTV which is 3v- same behavior..
tried to ground AC_DETECT , the result: TV makes attempt to start (red led turn off) but doesnt return to STDBY (red led stays off). of course no picture or sound and no PWR_SIG. (relay doesn't click)
i am starting to suspect main board because PWR_SIG is coming straight from the Controller and for some reason it is not supplied.
could the IC's ssc9500 or mip2f2 couse such symptom somehow?
Thanks.

[tom66]

Re: Toshiba 37AV600T - not powering on

OK, I had the very same problem with determining if AC detect was at fault on the 32WLT66S. It turned out to be the buck converter power supply for the main video processor was missing. Mine had absolutely no power LED though. The sub micom (yours may have one, or it may not) was not turning on the LED, so it looked like a normal dead PSU.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

is the 5 pins IC the buck converter ? if it is then there is 3.3v output from it.
if not- how does it look like?
by the way i think that the processor is getting supply voltage because the signal named PWRTV which also comes directly from processor does come up to 3v while TV attepts to start. (though didn't really tested it because i don't have schematics of r8j66614fp processor )
thanks..

[tom66]

Re: Toshiba 37AV600T - not powering on

On mine it was a 5 pin SOT23-5 package (looks like this: http://media.digikey.com/photos/Micr...6-SOT-23-5.jpg)

You could tell it was a buck converter because it had an inductor and capacitor nearby. Since it was a synchronous type, it had no buck diode.

There are also sometimes reset controllers near the ICs. Do you have the pin out for that main processor? Try and find the reset line.

The other possibility is a corrupted EEPROM, causing the set to get stuck in a boot loop.

[tom66]

Re: Toshiba 37AV600T - not powering on

One thing I did not mention previously is that almost every Toshiba LCD I have seen always does a self-test when first powered on. This means it turns on the PSU outputs, checks they are good for about 3~4 seconds, then turns off. If this self-test doesn't complete, the TV won't turn on, and will lock out further input. Maybe that is the problem -- PWRTV should turn on the outputs, but it doesn't.

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

from other Toshiba service manuals i found, the sequence is:
PWRTV (main to PS) -> AC_DET (PS to main) -> PWR_SIG (main to PS) -> PS turn on outputs.
is that correct?
the thing is that if i give 3v to PWR_SIG then while attempting to start, 24v appears on output to inverter (doesn't appear otherwise) .
i don't have the processor pinout, can't find it anywhere unfortunately.
r8j66614fp is the model of the processor .

[tom66]

Re: Toshiba 37AV600T - not powering on

24V appears, but do you also see 12VLCD?

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

nope, no 12VLCD. what does that mean?
what is the role of this signal?
thanks.

[tom66]

Re: Toshiba 37AV600T - not powering on

12VLCD powers the audio amplifier (on some models) and T-CON for the display.

[imp]

Re: Toshiba 37AV600T - not powering on

I see CapXon's on the secondary, almost always a source of failure. Not bulged but they may be dried up.

[tom66]

Re: Toshiba 37AV600T - not powering on

Wow, um, I didn't notice those -- Toshiba normally use decent caps. Shame Toshiba, shame...!

[carbonfiber]

Re: Toshiba 37AV600T - not powering on

not so fast blaming toshiba! it's actualy me who changed the caps while trying
to eliminate bad caps problem - without luck.
if i manage to get the tv running i'll change those to something decent.
by the way, maybe anybody knows what voltages should i expect on
the ssc9500 ic ? (16 pins chip which i marked earlier)

[tom66]

Re: Toshiba 37AV600T - not powering on

What were the original caps, out of curiosity? Probably Chemicon or Rubycon, that's what they usually use. Which are decent caps.