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-   -   Vizio L32 HDTV10A - Wont turn on (http://www.badcaps.net/forum/showthread.php?t=8731)

aliasdck 01-18-2010 11:33 AM

Vizio L32 HDTV10A - Wont turn on
 
2 Attachment(s)
Got another free LCD TV to play around with :spin:

I plugged it in and the amber standbye light came on and that's as far as it'll go. TV does not respond to any button pushes.

Power supply is in good shape. Only the 5v line is available during standbye, but I tested the 19v and 12v lines by tricking the power supply into turning on fully and everything tested fine... atleast without any load.

Started probing around elsewhere and determined that there was no sense voltage going out to the power button (or any other button). So of course the TV isn't going to be able to turn on.

Suspected there was a problem with the main board. Made sure it was properly receiving 5v from the power supply. Noticed there was a 3.3v regulator there and that checked out as well.

I was going to start downloading datasheets and probing around more but decided I might as well take some pictures and upload them here incase anyone had any insight. As I was taking the pictures I noticed an abnormality on one of the tiny smd components. It has a small bump in the middle...

Having trouble getting my digital camera to take good enough pictures but hopefully somebody can see well enough from them... I tried using the flash onetime on the closeup shot and it actually made the bump much easier to see (component circled in red)

The suspected bad component is U26... and it happens to be near the connector that goes out to the board with the power button on it. It's hard to read the part number partly because its so small but also because the bump is right where one of the letters should be. It's really hard to say but I think the part number is NTP4 or N1P4 or something similar.

I'll see if I can get better pictures but in the mean time I've attached the ones Ive taken so far.

den3720 01-18-2010 09:10 PM

Re: Vizio L32 HDTV10A - Wont turn on
 
Hi, I am sorry I do not have an answer for you but I am having the same problem as you on my display. If you don't mind me asking. How were you able to trick the power supply to come up?

Wizard 01-19-2010 09:10 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Did you carefully clean it? Could be flux glop sitting atop the transistor. Did you ohm it?

Usually NPN or PNP and it is general purpose because this is not high speed stuff because this is on this circuit for the function input (buttons).

Cheers, Wizard

aliasdck 01-19-2010 09:47 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Quote:

Originally Posted by den3720
Hi, I am sorry I do not have an answer for you but I am having the same problem as you on my display. If you don't mind me asking. How were you able to trick the power supply to come up?

One of the connectors has a line labelled "remote" which is connected to the main pcb. When the main pcb wants to come out of standbye, it puts 3.3v on this line which turns on the 12v and 19v lines on in the power supply.

I simply isolated the power supply from the rest of the tv and then used an external 3.3v supply connected + to the remote line and - to ground. :)

aliasdck 01-19-2010 10:32 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Quote:

Originally Posted by Wizard
Did you carefully clean it? Could be flux glop sitting atop the transistor. Did you ohm it?

Usually NPN or PNP and it is general purpose because this is not high speed stuff because this is on this circuit for the function input (buttons).

Cheers, Wizard

It appears the component is damaged... It does not appear to be flux.

Did some searching around and apparently its a common problem for this component to be defective in these sets. I found a post on fixya where a guy suggests removing u26 and replacing it with a diode. Doesn't seem like the best solution, but I tried it to see if it would fix the problem.

And sure enough it did. I installed a diode across (what I believe to be) collector and emitter. He says to install it across pins 2 and 3.

So yea. TV is working great now.

Wizard 01-19-2010 10:56 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
I thought that was for buttons as "function" is what it means.

And this hack is bad idea. Must install a suitable substitute transistor. I think this one uses PNP if it pulls 3.3V up when microcontroller pulls base gate up.

aliasdck 01-19-2010 11:25 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Quote:

Originally Posted by Wizard
I thought that was for buttons as "function" is what it means.

And this hack is bad idea. Must install a suitable substitute transistor. I think this one uses PNP if it pulls 3.3V up when microcontroller pulls base gate up.

Definetly. I'm not going to leave the diode in there, I just installed it temporarily to see if it would get the TV working again.

I believe its PNP also but I'm not positive atm. I'll see what I can find.

aliasdck 01-19-2010 12:19 PM

Re: Vizio L32 HDTV10A - Wont turn on
 
Got the parts and service manual for this TV off the net.

U26 is listed as a ASM809 which is a 3 pin Microcontroller Power Supply Supervisor. Its function is to keep the microcontroller in a reset state for a brief time during powerup, down and brownouts in order to avoid any errors during those time.

My U26 is faulty and is holding the microprocessor in reset. By installing the diode across pins 2 and 3, I am forcing the reset pin high and allowing the microprocessor to start (albiet without the safety of the brief time delay during powerup).

I'll order a new one, install it and post back.

meritks 01-06-2011 07:07 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Quote:

Originally Posted by aliasdck (Post 93416)
Got the parts and service manual for this TV off the net.

U26 is listed as a ASM809 which is a 3 pin Microcontroller Power Supply Supervisor. Its function is to keep the microcontroller in a reset state for a brief time during powerup, down and brownouts in order to avoid any errors during those time.

My U26 is faulty and is holding the microprocessor in reset. By installing the diode across pins 2 and 3, I am forcing the reset pin high and allowing the microprocessor to start (albiet without the safety of the brief time delay during powerup).

I'll order a new one, install it and post back.

I have the EXACT Same problem and Tv and found a replacement microprocessor. I am having trouble with the "Over voltage" and "Under voltage" thresholds, could you tell me which one you used?
Im looking at Mouser and they have 5 different which range from 2.93 to 4.63 v.
you input on this would be very helpful.
thanks, kyle

Th3_uN1Qu3 01-06-2011 07:51 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Since aliasdck mentioned the supply logic is on 3.3v, either the 2.93 or 3.08 volt will do.

lkvee 02-22-2012 11:54 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Friend gave me his after buying at one of each replacement board. I'm thinking both main boards (the original and the replacement boards) have a bad U26 ASM809 part. I'd love to know about progress here, too.

jgillilan 11-09-2012 08:49 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Has anything come of this thread. So far I have tried the resistor, the diode, and every other trick I found on the net. Still no tv on for me.

budm 11-09-2012 09:02 AM

Re: Vizio L32 HDTV10A - Wont turn on
 
Do you get the standby 5V OK? Check the voltage of the LDO REGULATORS? More info about what you have done so far will help.
http://www.badcaps.net/forum/showthr...391#post274391

http://s807.photobucket.com/albums/y...%20L32HDTV10A/

Keshetisrael 12-12-2013 01:05 PM

Re: Vizio L32 HDTV10A - Wont turn on
 
Quote:

Originally Posted by aliasdck (Post 93416)
Got the parts and service manual for this TV off the net.

U26 is listed as a ASM809 which is a 3 pin Microcontroller Power Supply Supervisor. Its function is to keep the microcontroller in a reset state for a brief time during powerup, down and brownouts in order to avoid any errors during those time.

My U26 is faulty and is holding the microprocessor in reset. By installing the diode across pins 2 and 3, I am forcing the reset pin high and allowing the microprocessor to start (albiet without the safety of the brief time delay during powerup).

I'll order a new one, install it and post back.

So What happened? Did you get the part? Did you install it? Did it work?

newtothis 12-12-2013 01:29 PM

Re: Vizio L32 HDTV10A - Wont turn on
 
Quote:

Originally Posted by Keshetisrael (Post 399854)
So What happened? Did you get the part? Did you install it? Did it work?

You do realize that this thread is a few years old and the OP hasn't logged on for two years?


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