Vizio 42" LCD VW42LHDTV10A Will Not Turn On

[Derrick8265]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

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[Derrick8265]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

Thanks again!

[ma777]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

Hey everyone,

This seems to be a great component level community! I have the same problem as the OP. The VIZIO light is orange and will not change to white when I hit power.
TV: VW42L-FHDTV10A

Below is a picture of my board.





I'm poking around at U19 and U20.

U19 (directly right of the top right corner of the heat sink)
Vin= 5.16 Volts
Vout= 4V initially and then drops to 2.503
ADJ= 3v initially and then drops to 1.255 (this seems strange?)

U20(Directly left of top corner of heat sink)
Vin= 3.3
Vout = 1.8 (these are higher at first and then go to these values)
ADJ = .557

These changing voltages seem strange to me because when I tested another 1084-0808HL the values were constantly steady.


Thanks

[ma777]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

F2 is for the switched 12V supply.

Just quoting you so you get a notification.


With the 1k resistor soldered on my PS_ON pin is reading around 4.5V. Using my DMM without bulbs connected I read 12V and 24V just fine. But with bulbs connected, I can't get a reading. I'm assuming having a load connected is causing the problem. The 1157s will not illuminate. So, at this point it looks like my power board and main board are shot?

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

OK, we need to find out first if the power supply board is getting the PS-ON command signal or not from the main board.
BTW, are you using the low filament or high filament in the 1157, it should be the low filament since the cold resistance may be too low and cause the power supply to shutdown when tested with lamps due to too high inrush current. You leave the load for the 12V not connected just to test the power supply function since the 12V and the 24V are generated by the same power transformer.
Your regulators sure do look right with the Voltage changing.

[ma777]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

I don't think I am getting PS_ON from the main Board. With my DMM connected to PS_ON wire from the main board, I show 0 Volts when I press the power button. I am using the low filament but I will double check and try again.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

I don't think I am getting PS_ON from the main Board. With my DMM connected to PS_ON wire from the main board, I show 0 Volts when I press the power button. I am using the low filament but I will double check and try again.

You mean all the cables are connected between the PS board and the main board and the PS-ON is showing 0V? If that is the case then we need to look at the main board.

[ma777]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

Okay just retested with no load. I doubled my resistance to 2k between PS_ON and 5V stand by. PS_ON is now reading 3.88V. With NO load I am getting 12V and 24V. I hooked up one bulb to 12V and had it lit up for about 15 seconds before turning it off. Then I went and wired up 2 bulbs in series for 24V rail. No dice, none of the bulbs turn on now. (100% sure I am using low filament.) I am hearing some whine from a capacitor not sure which.

Edit: Yes, with everything connected between main and power boards PS_ON shows no signs of life. I was wanting to double check my power board as well because it seemed liked an easy test.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

OK, remove the two lamps that are connected in series for testing the 24V and then connected to the 12V output only, so basically we are testing the 12V output only with 24v LAMPS (two 12V lamps in series) and no load to the 24V.
The PS-ON should be present when the power switch is activated even the 12V/24V is not present.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

BTW, how about the DCV readings of the 1117 regulator ICs:
U17, 21, 22, 44?

[ma777]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

Okay, rewired everything back to factory. (Vizio Light is orange) DMM is connected to ground and PS_ON. Pressing the power button gives no change in reading on the meter. Vizio light remains orange.

With the 2k in place jumping between PS_ON and 5V standby, with just one 12V light on the 12V pin it refuses to stay on. It will turn on for about a quarter of a second and then turn off.

When I tested it earlier today just 12V seemed to work fine and now it's not working. Maybe because the set had been completely off for a few days?

I also tested the 12volt pin with two bulbs and got the same result.

Is there anything you want pictures of?

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

Lets make sure the main board regulators are good first, then deal with the power supply problem next, it now looks like we have to fix two boards.

[ma777]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

What are the correct pin names? Don't want to say the wrong names.

U17-----------------------
Top-3.294
Left-2.053
Middle-3.295
Right-5.16

U21-------------------
Top-1.236
Left-0
Middle-1.236
Right-2.499

U22------------------
Top-3.297
Left-2.058
Middle-3.297
Right-5.18

U44------------------------
Top-0
Left-0
Middle-0
Right-0

Edit: A little history of the TV.
2HDMI ports stopped working a few years ago
The final HDMI port went out about a year ago
The TV started turning off on its own over the weekend
This increased in frequency until sunday when the TV would no longer power on.

I'm pretty sure It's my fault because I think on thursday I was being lazy and plugged in a vacuum on the same power strip.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

What are the correct pin names? Don't want to say the wrong names.

U17----------------------- Adjustable Vreg. Good: 1.25Vef + 2.053 (Adj pin) = 3.303V (Output centerpin/tab).

Top-3.294
Left-2.053
Middle-3.295
Right-5.16

U21------------------- Fixed Vreg. Good: 1.25
Top-1.236
Left-0
Middle-1.236
Right-2.499

U22------------------ Adjustable Vreg. Good: 1.25Vef + 2.058 (Adj pin) = 3.308V (Output centerpin/tab)

Top-3.297
Left-2.058
Middle-3.297
Right-5.18

U44------------------------ Need to find out why there is no input Voltage.
Top-0
Left-0
Middle-0
Right-0

Edit: A little history of the TV.
2HDMI ports stopped working a few years ago
The final HDMI port went out about a year ago
The TV started turning off on its own over the weekend
This increased in frequency until sunday when the TV would no longer power on.

I'm pretty sure It's my fault because I think on thursday I was being lazy and plugged in a vacuum on the same power strip.

Need to find out why U44 has no input, it may be fed by the switched 12V which is fed to 5V Vreg 7805 IC and then its output then feeds U44 input pin.

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

OK, I look up old threads. The 12V has to work for the U44 to get input Voltage.
https://www.badcaps.net/forum/showth...&highlight=u44
We never did find what went out on the main board.

[ma777]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On



Two bulbs on 12V line and DMM on 24V line.. It stops working when I try to connect bulbs to the 24v line. BUT, If I connect the white back-light inverter cable the 12V line functions fine. If i disconnect it, the 12v line won't work!?


EDIT: With PS_ON Jumped
U44----------
Top-9.5
left-8.3
middle-9.57
right-11.08

Seems to be something wrong here... My V-in should be 5 volts at the maximum right?

[budm]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

https://cdn.badcaps-static.com/pdfs/...bb102c88cc.pdf
It can take up to 20V, 15V is the recommended input V.
8.3V on ADJ pin + 1.25Vref = 9.55V so it is OK.

[ma777]

Re: Vizio 42" LCD VW42LHDTV10A Will Not Turn On

Ahh okay I just took a quick glance at the data sheet and saw 5v. Didn't scroll down to max input.

I think I've tested everything you said so far... What else can I check?

All my caps appear to be good.