Vizio VW42LFHDTV10A

[Chancey]

I read a recent post by drpj23 and am suffering a similar problem. I chose to make a new thread as to not hijack his thread. The information I have below is from what I posted on another site and figured a C&P would suffice. I also viewed the pdf that Mr Bill posted on that thread and the DC-DC Converter testing procedures differ from the ones I have. So that may add some level of error for my testing...

C&P
OK...Page 9-5 of the manual indicates the step by step procedure to diagnose the DC-DC Converter. The problem I am having, is when powered on...no powerup.

I checked the first step that claims J1 pin 10,11 and 12 should have 5v. In fact, it does. Next step says to power on the TV. The only indication I have of power up is the vizio orange light that turns white. Then u must check J1 pin 2,3,4 and 5 for 12v. (On the VW42L, pin 5 is not populated...must be in general for all TV;s that follow this design scheme.) There is no voltage on these pins and PIN 1, shows NO voltage for PSON and F2 is good that provides the 12v.

I found a 3.3v reference on the power supply, removed pin1 from connector on mainboard, to prevent back feeding voltage, and jumpered to trick PS to come on. BAM!! TV powers up on I have FULL functionality and menu's and the 12v is present on 2,3 and 4.

Here's my question...pin1 is not fed from the power supply but the main board? The walkthrough say's to check the PS. Is pin 1 not in fact a toggle that is triggered from the mainboard to power on the switch mode?

To add some more information, the PS is: FSP254-3M01 and the mainboard is a 0171-2272-2434

[retiredcaps]

Re: Vizio VW42LFHDTV10A

Some Vizios have bad voltage regulators on the main board. See my sig file below on how to

1) post pictures of your boards

2) test voltage regulators

3) report your readings as per my guide

[Chancey]

Re: Vizio VW42LFHDTV10A

Here's the pictures...I'll post the regulator readings in a sec.

[Chancey]

Re: Vizio VW42LFHDTV10A

Ok...Updating pictures of the regulators and also the readings of the IC's. My apologies for not having the info up sooner. Got side tracked on another project.

All reading were done with TV on (assuming orange standby light turning white means TV is on)

U16
AZ7805T
Pin 1-0
Pin 2-0
Pin 3-0

U44
1117L
Pin 1-0
Pin 2-0
Pin 3-0

U17
AMC1117
Pin 1-2.09
Pin 2-3.35
Pin 3-5.13

U21
AMC1117
Pin 1-0
Pin 2-1.25
Pin 3-2.50

U22
AMC1117
Pin 1-2.07
Pin 2-3.33
Pin 3-5.18

U20
1084
Pin 1-0.54
Pin 2-1.79
Pin 3-3.27

U15
1084
Pin 1-2.05
Pin 2-3.30
Pin 3-5.12

U19
1084
Pin 1-1.25
Pin 2-2.50
Pin 3-5.12

[retiredcaps]

Re: Vizio VW42LFHDTV10A

All reading were done with TV on (assuming orange standby light turning white means TV is on)

U16
AZ7805T
Pin 1-0
Pin 2-0
Pin 3-0

U44
1117L
Pin 1-0
Pin 2-0
Pin 3-0

Recheck the above two. They is something obviously wrong with those.

[budm]

Re: Vizio VW42LFHDTV10A

So if you forced the PS to come on and all he functions on the TV works with good pictures and sounds, then what voltages do you get at those UXX that shows 0V reading on all three pins if you leave the jumper in place?
PS_ON signal is generated by the Main board when TV is turn on and this signal is fed into the PS (Power Supply) board PS_ON pin, >3VDC = ON, 0~.5V = OFF.

[Chancey]

Re: Vizio VW42LFHDTV10A

Recheck the above two. They is something obviously wrong with those.

I agree...I checked and rechecked. Obviously one is a 5 volt regulator and it's right next to the audio amplifier IC. Odd that when I trick the PS in coming on everything works...gonna jumper again and get back with ya on that one.

[retiredcaps]

Re: Vizio VW42LFHDTV10A

For U44 and U16, see if they are shorted. With power off and lcd unplugged, measure the resistance between pins 1-2, 1-3 and 2-3. Report your resistance measurements for all 3.

[Chancey]

Re: Vizio VW42LFHDTV10A

With system jumpered:

U16
pin 1-11.44
pin 2-0
pin 3-5.01

U44
pin 1-8.43
pin 2-9.69
pin 3-11.46

Resistance readings:
U16
1-2 I stopped @ 10k...acted like charging a cap
2-3 2k and rising, cap again
1-3 15k and rising

U44
1-2 .300 ohms <----maybe??
2-3 18.4k steady
1-3 5.4k and rising

Uncertain with the IC U44 being .3 ohms without looking at the datasheet. What gets me, and also worries me cause I know it will cause damage if I leave the TV on while jumpered, why is the stupid thing initializing post when jumpered if the IC's r bad..granted it's the 3.3v not being satisfied. The power button, un-jumpered, will only turn TV on and then I have to kill AC and wait 3 minutes to try again. Power button will not turn TV off. However, jumpered, the TV will power on and off with the button.

You think you know electronics and you get something like this thrown in your lap.

[Chancey]

Re: Vizio VW42LFHDTV10A

Best guess from anybody would be better than what I have. Trying to help out a 75 y/o man on SS without having to buy him a new main board.

BTW, off subject, LOVE the site. Never seen so much information with this high success rates. If I get this fixed or not...gonna def donate to the sites fund.

[retiredcaps]

Re: Vizio VW42LFHDTV10A

With system jumpered:

U16
pin 1-11.44
pin 2-0
pin 3-5.01

U16 is working fine as it is a 7805 type so pin 3 is correct.

U44
pin 1-8.43
pin 2-9.69
pin 3-11.46

Technically U44 is doing its job of pin 1 + 1.25V = output voltage.

U44
1-2 .300 ohms <----maybe??

Uncertain with the IC U44 being .3 ohms without looking at the datasheet.

Hmm, that indicates that something might be shorted. Or there could be a low ohm resistor between pin 1 and 2. What is the resistance of R478 and R479? What is the resistance of C217?

[Chancey]

Re: Vizio VW42LFHDTV10A

What is the resistance of R478 and R479? What is the resistance of C217?

Ok...I need to go to DMM reading class. My meter isn't autosensing and pins 1-2 on U44 are 300 ohms.

R478 300 ohms
R479 1.99K (2K)
C217 1.14K

The initial readings of U16 and U44, PS unjumpered are zero on all pins. The voltage readings I gave after intial readings are with me jumpering the A1 on the PS to J1 pin1. So, factory setup...those two IC's have no in, adj or out voltages.

[budm]

Re: Vizio VW42LFHDTV10A

According to my calculation, the output voltage of this U44 should be 9.583V.
1.25 x (1 + (2000/300)) = 9.583V.

"However, jumpered, the TV will power on and off with the button" but if you check the 12V and the 24v OUTPUTS, they will still be there even when you turn off the TV (jumper in place).

[Chancey]

Re: Vizio VW42LFHDTV10A

According to my calculation, the output voltage of this U44 should be 9.583V.
1.25 x (1 + (2000/300)) = 9.583V.

"However, jumpered, the TV will power on and off with the button" but if you check the 12V and the 24v OUTPUTS, they will still be there even when you turn off the TV (jumper in place).

I agree with the calculations...just wanted to clarify that the first readings were indeed correct and 0 volts. (Post #4)

On the second part, negative ghost rider...power off, no 12v or 24v. Power on, voltages are present.

You are talking about J1 for 12v and the plug going to inverters for 24v, right? I attached picts...

I can program and Allen Bradley PLC5, SLC500 and ControlLogix with my eyes shut...but for some reason, this is kicking my rear....Please don't take my humor as harsh, I am very appreciative of any knowledge I can gain from yourself or retiredcaps....or anyone for that matter

Just reread your post on #6...From some of the information I have been reading on this site, is that a normal voltage for PS_ON for every TV? (granted some will be different I'd imagine...gonna remember that one)

[budm]

Re: Vizio VW42LFHDTV10A

Yes, about 3Vdc for PS_ON to Bias on a transistor in the power supply section, it is not at logic level like the digital circuits. That does not make sense that the 12 and the 24V go away when the TV is off since we are forcing it to be on by jumping the PS_ON pin, now when I look at the way you are jumping the PS_ON, you use the 3.3V form one of the power supply pin which I have never see 3.3V power supply section on this board before. The way we force the power supply to be on, we use 1~3K resistor between the 5VSTBY and the PS_ON pin to turn on the power supply.
I am curious to know if that 3.3V feeding the PS_ON is turning ON and OFF by the main board. Can you tell me which pin on the connector you are using is putting out 3.3V for the jumper?
This is how I test the power supply by itself:
http://s807.photobucket.com/albums/y...ply%20testing/

[budm]

Re: Vizio VW42LFHDTV10A

The pins labeled with C1, B1, A1; they are feed through connections, the power supply board is used as the junction box only, those pins are not connected to the power supply circuits at all.
They are
Dimming signal (0~5V, 5V= max brightness) if inverter board is setup for analog dimming controlled.
PWM Dimming (it uses PWM for brightness control) if the inverter board is setup for PWM dimming controlled.
Backlights ON/OFF (for turning on the inverter, >3V = on).

To have backlights work, it needs two voltages, one is the swiched 24VDC which is controlled by the PS_ON, and then the Inverter ON/OFF signal.
So right now you are using the Inverter ON/OFF to turn on the power supply AND then inverter ON/OFF, that is why the 12/24 go away when you turn off TV. There is no 3.3V power supply section on that power supply board.
If you look at the bottom side of the board you will see how A1, B1, and C1 are routed, this is very common setup for most TV to keep the wiring clean. I can draw you the simple diagram if you need it.

[Chancey]

Re: Vizio VW42LFHDTV10A

Would it help if I took some pictures of the inverter board? To determine whether or not it's PWM or analog...the diagram may help. But I may end up having to remove the main board and tracing where pin 1 originates from. At somewhat of a loss...

[budm]

Re: Vizio VW42LFHDTV10A

If you can get the LCD panel model number, then you can get the spec sheet which will tell you all the pin out of the Inverter board and the T-CON board.

[budm]

Re: Vizio VW42LFHDTV10A

Simplify diagram.
Example of LCD panel spec, see page 15 for control signal for the inverter board.
We know the inverter board is OK so no use to look at it.
You need to figure out the PS_ON pin on the Main board, and since the TV functions OK when the PS_ON is forced ON, more likely the transistor interface that control the PS_ON line is stuck ON so it grounds the PS_ON line.

[Chancey]

Re: Vizio VW42LFHDTV10A

WOW!! LOL, I feel a tad in over my head...but, will force on through the madness and try to whip this puppy. Thnx budm...I'll report back what I find on the main board. Little overwhelming...only a hobby repairer