Vizio VX32L turns on with backlight, no video or sound

[retiredcaps]

Re: Vizio VX32L turns on with backlight, no video or sound

(they are all AMC1117):

Is there a suffix or another line after AMC1117. For example AMC1117-33 indicates that the correct output is 3.3V DC. AMC1117-18 is 1.8V DC output.

[yesfan2]

Re: Vizio VX32L turns on with backlight, no video or sound

Hi, they all have the markings

AMC1117
F0646J

Thanks!

[cashkennedy]

Re: Vizio VX32L turns on with backlight, no video or sound

I purchased a VX32L on craigslist with the same problem, folowed the service manual to diagnose the DC-DC regulators. The U33 regulator just like everyone else here who has succesffuly fixed there's, was the problem.

When testing U33 to ground I would get the following to the CASE GROUND (do not test with the 3rd pin as that is an adjustment pin, not a ground)

In to case ground > ~3v
out to case ground > ~2.2v

U33 is supposed to have 5v in and 3.3v out. I was worried that i wasnt getting 5v to it, and that U33 was not the problem, but i bought the part anyway and soldered it in, and the TV works perfectly.

The part number is AMC1117, as has been said here already, that is a really generic part that comes in adjustable or fixed versions. The board clearly uses an adjustable version. I purchased STMicroelectronics LD1117SC-R http://www.mouser.com/Search/Product...511-LD1117SC-R and it worked fine.

[cashkennedy]

Re: Vizio VX32L turns on with backlight, no video or sound

Well I thought it was fixed, but then it went bad after ~ 12 hours of testing.
It turned off randomly twice during the 12 hours, so i thought it was heat, but then the next day after it being off for 10 hours it started compleatly then a few seconds later went to the white vizio logo, but not able to be turned off using the power switch.

I tried a different brand adjustable 1117, but it didnt work right when i soldered it on, but after probing it a while it worked for a bit (i think maybe it works if i accidentally bridge the input (in the broken state around 3.0v), to the output (supposed to be around 3.3v)...

Im concerned my error is slightly different then other people as i dont just get a lowered output, but also dont appear to get 5v to the input. The testing path says to consider replacing U1 (the 8 pin IC that gives 5v to many regulators once the tv is switched on, part 4953gm), but i measured 5.0v on all the output pins from it.

Originally before my regulators arrived by mail I replaced the electrolytic cap that filters the 5v input area to ground with a panasonic EB, and although EB probably isnt the proper cap for this position, it didnt work after replacing just the cap, and i wouldnt think the cap would go bad this fast, so i dont think its the cap , although i could be compleatly wrong.

So my question is basically is it normal to have a lowered input voltage to ground when a regulator fails, or is there likely a different problem then the regulator, such as the cap or one of the tiny smd caps, or the IC that provides the 5v to this regulator.

In the attached drawing the adjustment pin is connected by 2 blue resistors to both the output and the ground, the resistor to the output is ~ 100ohms, and the resistor to ground is 150 ohms.

[budm]

Re: Vizio VX32L turns on with backlight, no video or sound

Since the input oft the 3.3v regulator is fed by the REGULATED 5V regulator, may be your 5v regulator is bad or bad filter caps or too much load on 5V regulator itself.

[cashkennedy]

Re: Vizio VX32L turns on with backlight, no video or sound

Well ive tested all the other regulators and theyre getting 5v input (of the ones that are supposed to get 5v obviosuly ), so i dont think its a problem where the 5v supply is low. and considering the U1 (which is a dual chanel p fed mosfet i think?>) outputs 5v , while at the same time i only read 3.0 v input to the regulator, so i think it cant be the U1 mosfet.

Curiously there is a second dual chanel p fed mosfet called "U32" that your arent asked to test anywhere in the DC-DC conversion testing path. It is the same part number as U1. But the pathway says that if U33 is low to consider replacing U33, or U1, it does not say to consider replacing U32.

I would assume some zener diode or similar part prevents the u1 pin that feeds U33 from seeming low, and so whatever is draining the voltage input to U33 is after that diode. Im not sure what all could drain the input voltage, perhaps someone here has seen something like that happen, maybe the filtering caps?.

[cashkennedy]

Re: Vizio VX32L turns on with backlight, no video or sound

I havent tested caps much, as usually i only replace them if theyre bulging, but i used my multimeter on a high ohm setting to read resistance on a few of them, and was expecting to get the resistance to go up, which most of them did, but between the output of u33, and the ground, in multiple places since it is filtered a few places, i get a resistance of 270ohms, which does not change, i see thats comming from the 2 resistors that i explained above handle the adjustment pin, but is that normal? cause it seems like it might defeat the purpose of having filter caps if the output and ground are connected by a total of 280 ohm resistance.

So perhaps the ouput is almost shorted to the ground and this is causing a huge strain on u33, causing its input and output to both be lower? Im not sure how regulators work though, so not sure if a huge current going through it can lower the input.

Anyway i know very little about how circuits like these are designed, so just tell me if thats not where the problem is.

[cashkennedy]

Re: Vizio VX32L turns on with backlight, no video or sound

I think i overcomplicate my posts and people dont reply

1) Can a faulty regulator cause the input voltage to decrease?
2) Is it abnormal for the output of the regulator to be only 175 ohms to the ground.
3) What would usually cause / or occur before the regulator in the circuit that might lower the input voltage besides a bad dual channel mosfet that is sending the 5v signal to most of the regulators on the board

Either way if i dont get any replies I guess im going to replace the dual channel mosfet, and replace again the capacitor thats between the input and ground.


And as a reply to budm : this regulator that fails on most people converts 5v to 3.3v and then passes that 3.3v on to 2 other regulators that create 1.25 and 1.5v for the memory and processor i would assume. The part that i replaced was the 5v regulator that makes the 3.3v, and replacing it seemed to fix the problem for a while, and both replacement regulators i bought were rated for higher wattage then the original.

[cashkennedy]

Re: Vizio VX32L turns on with backlight, no video or sound

I tried to do a 12 hour test again, and it turned off after about not changing the channel or volume or anything for 4 hours. When you do a 12 hour burn in test do you ever have to change the channel every 2 hours or so to prevent the tv from turning off? or is mine turning off from a problem most likely. I have reset the firmware so obviously sleep shouldnt be on / affecting anything.

When i relooked at the problem last night i realized the 5v filter cap was continous with all the other 5v regulator inputs and 5v filter caps, but the specific u33 regulator in question was not continous. So i figured the pad / traces were unreliable and soldered a short wire between the input on the regulator to the 5v filter cap.

[kevinm34232]

Re: Vizio VX32L turns on with backlight, no video or sound

I need some help please. I have a VX32L that powers up with an all white screen. I tested all the voltage regulators described in this thread with the following results:

u33 in 5.08v out 3.30v
u2 in 5.08v out 3.29v
u4 in 5.08v out 3.31v
u8 in 5.12v out 3.32v

u7 in 3.30v out 1.27v
u9 in 3.30v out 1.52v

Seems to be inline with working TV voltages. Any idea what else I can check? I hear that a fuse can cause this not really sure what I'm looking for, thanks!

Also, plugged in DVD player to RCA inputs and switched inputs and DID get sound (but not very loud when maxxed). If I unplug LCD controller board harness from main board backlight still comes on but not a bright white screen like when it's plugged in.

[selldoor]

Re: Vizio VX32L turns on with backlight, no video or sound

Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

It will be useful if you can say how the fault started flashing screen ?? etc and a bit about yourself - skills tools etc.



White screen can be caused by a number of things and often by a fuse on the Panel Board. Also loose cables can cause this. For some reason or other there does not seem to be any pictures of this board so I cannot show you where the fuses are. Try reseating all cables.
If you post good clear pictures I will look and try and help you find them.
Do all the on off controls and the led work?

[kevinm34232]

Re: Vizio VX32L turns on with backlight, no video or sound

Yes controls and on/off working, do you want a pic of the main board or the T-Con board? Vizio logo goes orange to white when turned on, then to orange when turned off.

[selldoor]

Re: Vizio VX32L turns on with backlight, no video or sound

May as well do both while youve got the camera going - its only to help you locate the fuses at the moment. Go carefully if the T con is attached to the panel.

[kevinm34232]

Re: Vizio VX32L turns on with backlight, no video or sound

Pics of VX32L main and T-Con board...

[selldoor]

Re: Vizio VX32L turns on with backlight, no video or sound

Ok Main board pic is not really clear enough for trouble shooting, having said that there are two fuses I can see just above the second connector from the left.
They are white rectangles with gold? ends- board may be marked as F1 & F2 but I cant read it.
On the Tcon there is a white fuse near the right hand end of the connector at the bottom of the pic - it looks to have a red marking on it.

There may be others - now you know what to look for you can look.

To test these POWER OFF for 5 mins Meter set on OHMS 200 one probe on each end - should be the same as touching the probes together. Post results

[kevinm34232]

Re: Vizio VX32L turns on with backlight, no video or sound

All 3 fuses tested good Anything else I can check?

[budm]

Re: Vizio VX32L turns on with backlight, no video or sound

What DC voltage do you get at the T-CON fuse?

[kevinm34232]

Re: Vizio VX32L turns on with backlight, no video or sound

5vdc

[budm]

Re: Vizio VX32L turns on with backlight, no video or sound

I am not sure if your panel is 5V or 12V panel, most 32" I worked on use 12Vdc for powering the T-CON. Can you see the label on the panel so I can look up the spec?

[kevinm34232]

Re: Vizio VX32L turns on with backlight, no video or sound

The part # on the label is 59.31T03.061/01
Hope that helps