Vizio VX42LHDTV10A stuck in standby after going haywire.

[ktulu909]

Ok folks,been reading for the last 3 hours and could use a little guidance.I have a unit that went completely haywire last night.It displayed horizontal multicolor lines and was making a terrible squealing through the speakers and would not respond to any button presses.It had to be unplugged to make it stop.

After letting it sit for about an hour,I plugged it back in and get the orange Vizio logo and nothing else.No response to buttons,or remote.Just an orange vizio logo.

After reading the forums,I have found some good advice on where to start looking,but so far have found nothing definitive.I work in car audio and security and have a decent electronics background.Im proficient with a multimeter and am completely comfortable testing anything you guys can point me towards.

I have visually inspected every capacitor in the tv and nothing has ruptured or shows any sign of buldging.This model has the singal long inverter board and the capacitors look good there as well.I have also tried powering on the unit with the inverter board unplugged and still no dice.It just wont do anything.

I tested all the outputs on the power supply and the only thing that actually has output are the 5V lines.Is this normal?

If anyone has any ideas on where to go from here,Im all ears and look forward to hearing from you all.

MODEL- VX42L HDTV10A
Serial LSABMBH4614174
Date of Manufacture 11-07
Part Number 10235030022

[retiredcaps]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

1) Post clear focused top down view pictures of all your boards following the instructions in my sig file below EXACTLY.

2) 5V indicates that your standby is working.

3) The main board should be sending a signal to tell the power board to turn on the SMPS. This signal is sometimes called PS_ON and is usually 3V or higher.

[budm]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

That is the 5VDC Standby power supply, it always running, the other power supply sections (12v for the sound, and 24v for the backlights inverter) are controlled by the main board, the main board will send out the PS_ON signal to the power supply to turn them on when power switch is activated. Please post good clear pictures of the whole rear view of the TV so we can see how the boards are connected together, then good pictures of the power supply board both top and bottom sides, connectors so we can see the labels on them. There should be a pin with PS_ON (or PWR_ON), measure the DC voltage on that pin (black probe of the meter to the chassis) with the TV off and with the TV on.

[infringer]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

The main board is the one with all of the video connections I would say that if your TV is still indicating that it is powering on then it is likely that you need to replace this board look for things that may be bad on this board as well like a blown cap or something ... If not it is hard saying what it is look at the screen prints and check for blown fuses marked F in most cases... for instance F5 or F12 or F2 something along them lines do a continuity check some of these may not look like fuses but they are SMT variations of fuses. beyond that it gets kind of difficult to diagnose anyways good luck with your project.

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

Yea,all the fuses test under 1 ohm,so I assume (you know that that gets you) that theyre good.Also it seems that the larger heat sink on the power supply will provide you with a nice little 56v tingle when plugged in,is that normal?

Sorry about the quality of pics,my phone is all I have

[retiredcaps]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

Also it seems that the larger heat sink on the power supply will provide you with a nice little 56v tingle when plugged in,is that normal?

Heatsinks are live and can potentially be 400V DC depending on PFC or not. Don't touch them.

On the power board, there is a PS_ON pin. When you press the on/off button, does this pin change from 0V to 3V or higher?

If not, there are a ton of voltage regulators on the main board. You will have to measure them all to see if anyone are bad. Vizio's have a problem with voltage regulators failing.

[tom66]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

I have encountered the "going haywire and then not working problem before", but not on a Vizio (as they aren't sold in the UK.) It was on a cheap China-brand TV.

It turned on a supply on the motherboard had failed while the user was watching, leaving them with a screen full of vertical coloured lines because the T-con board was not receiving a proper signal any more. When they tried to power it up after unplugging it, the power LED would come on but that was it... and then it wouldn't shut down again until unplugged.

So I would carefully check all secondary supplies pn the motherboard especially the dreaded U33.

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

Sorry for the lack of an update folks,Ill be going back over there tomorrow to look at a few more things and see if the power supply is receiving the signal to turn on and we'll go from there.

What would be acceptable voltages on the the regulator pins on U33 and the other ones that look similar?

[retiredcaps]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

What would be acceptable voltages on the the regulator pins on U33 and the other ones that look similar?

If you are lucky, there distinguishable part numbers on each chip that reads something like 1117-33 where the suffix tells you the correct output voltage +/- 1%. So 1117-33 designates 3.3V +/- 1%.

The output pin is usually the middle pin.

If there are no part numbers, common output voltages are 1.8, 2.5, and 3.3. Anything that reads 2.9, 3.1, 3.5, etc is likely bad.

I suggest you list and measure them all. Measure all the pins except the fat tab.

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

SHould those pins be showing any kind of voltage in standby,considering thats all I have lol.Heading over tomorrow afternoon to work on it some more.

[retiredcaps]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

SHould those pins be showing any kind of voltage in standby,considering thats all I have lol.

Standby 5V power is required in order for the main board to work.

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

OK here we go.


Looking at the regulators as the fat tab being the top,listing pins left to right.

U2- Part number
AMC1117
F0734F
PIN 1 2.03 VDC
PIN 2 3.28 VDC
PIN 3 5.10 VDC

U8 Part number
AMC1117
F0734F
PIN 1 2.02 VDC
PIN 2 3.26 VDC
PIN 3 5.12 VDC

U33 Part number
AMC1117
F0734F
PIN 1 2.02 VDC
PIN 2 3.26 VDC
PIN 3 5.10 VDC

U7 Part number
AMC1117
F0734F
PIN 1 0.00 VDC
PIN 2 0.71 VDC
PIN 3 3.27 VDC

U9 Part number
K1117S15
735
PIN 1 0.00 VDC
PIN 2 1.50 VDC
PIN 3 3.27 VDC

Well,there you have it.I hate to assume,but Im going to go out on a limb and say that U7 and U9 are bad.Now this is the part where you professionals tell me if im right or not lol.

Anything else you guys want me to check?

Oh and no,no voltage is showing on the PS_ON line when the power button is pressed.

[Jasgriff]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

http://pdf1.alldatasheet.com/datashe...C/AMC1117.html

There is the datasheet for those regulators this will allow you to chack and see if they are in range or not.

Can you edit the numbers so we know what each line says? its hard to look at what they are with them in 1 big row as some of the numbers wont be relevant.

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

I appreciate you posting the datasheet,but unfortunately the info is a little out of my league lol.Ill stare at it for awhile and see if anything jumps out and I can put 2 and 2 together.

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

Ok after looking at the datasheet for 15 minutes,I see that U7 and U9 are receiving lower voltage on the input pin than the others.Does that mean that my problem lies elsewhere before those two components?Or are those two regulators supposed to have a lower voltage on them?

Also,whats the significance,if any,of U9 being a different part number than the others?Also the datasheet doesnt show my specific part number (ending in 734) anywhere.

Ok,now im officially confused lol.

[Jasgriff]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

They way they work is like this.

AMC1117 This is the part number F0734F is possibly underneath the part number im guessing? so this might be a date code.

If your part number was AMC1117-1.8 this would tell us that your should have 1.8v on Pin 2 which is out. If it was AMC1117-2.5 then pin 2 should be 2.5v.

So if you look at K1117S15735.... Part number K1117S with the next 15 meaning 1.5v on pin 2.

Does that make sense?

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

Can you edit the numbers so we know what each line says? its hard to look at what they are with them in 1 big row as some of the numbers wont be relevant.

Edited.There ya go

[Jasgriff]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

Ok on Pin 1 of U7 are there 2 resistors connected to it?

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

They way they work is like this.

AMC1117 This is the part number F0734F is possibly underneath the part number im guessing? so this might be a date code.

If your part number was AMC1117-1.8 this would tell us that your should have 1.8v on Pin 2 which is out. If it was AMC1117-2.5 then pin 2 should be 2.5v.

So if you look at K1117S15735.... Part number K1117S with the next 15 meaning 1.5v on pin 2.

Does that make sense?

Thank you for the breakdown.That makes perfect sense on the K1117,but unfortunately not so much on the AMC1117 to me.Please be gentle,Im trying to soak all of this in.

[ktulu909]

Re: Vizio VX42LHDTV10A stuck in standby after going haywire.

Ok on Pin 1 of U7 are there 2 resistors connected to it?

Yes there are,two microscopic resistors.