Vizio vw37l Amber light only will not power on

[swwww]

Hi all.

I am trying to diagnose my visio vw37l

I have only orange light

5vdc standby voltage present on output of power supply but no "ps on" signal present at power supply when power button pushed.

I was reading another thread and they suggested unplugging the inverters (the other two output plugs of power supply i'm assuming) with no change.

anyone have any ideas on what to test to isolate (seems like main pcb maybe?)

Two fuses i could find on main pcb by the input cable test fine

I also have my 5vdc control voltage at switch/button board

thanks

scott

Update--- I unhooked all connectors on power supply and hooked 3vdcto "ps on" input pin, the power supply voltages 12vdc and 24vdc are present on output pins of the 3 p/s connectors. so p/s appears to work when it gets the "on" signal..

any ideas why the "p/s on" is not coming from main pcb?

Added pics--- Thanks for the reply

[Dgtech]

Re: Vizio vw37l Amber light only will not power on

Post a picture of the set layout of the boards internal. Then post pics of the boards close up, starting with the power board.

[budm]

Re: Vizio vw37l Amber light only will not power on

I would check all the voltage regulators on the main board, please see the link below my signature on how to check the regulators.

[swwww]

Re: Vizio vw37l Amber light only will not power on

Tested all the v-regs I could find... Aside from u-3 2nd of the largest two risiding on the right side not having any input power ( i am guessing this part of the board is not active in standby) all looks good except u7 which is in the middle upper center just below connector has input but no output. Doe this mean its bad? I was getting readings i that trust/understand trying to test the resistor and cap in the area.. (Differed from other readings (ohms) i tried to sample from caps in circuit next to similar vregs in area )

Admittedly I am traveling a smidge beyond my experience level so my apologies if i am saying incorrect methods

thanks for any help

[budm]

Re: Vizio vw37l Amber light only will not power on

Can you report all the readings in the format as shown by retiredcap: https://www.badcaps.net/forum/showth...999#post300999

U33 is usually bad, same for U7.

[swwww]

Re: Vizio vw37l Amber light only will not power on

u7
amc1117
pin1 -0v
pin2 -.5v
pin3 -3.36v

u33 and all other amc1117's i could find were all the same readings
amc1117
pin1 -2.1v
pin2 -3.36v
pin3 -5.15v

u10
1084
pin1-1.41v
pin2-2.66v
pin3-5.15v

u3
az7805t
pin1-0v
pin2-ov
pin3-85mv

thanks again

scott

[retiredcaps]

Re: Vizio vw37l Amber light only will not power on

u7
amc1117
pin1 -0v
pin2 -.5v
pin3 -3.36v

u3
7585t
pin1-0v
pin2-ov
pin3-85mv

U7 pin 2 should be 1.25V DC. Double check your readings.

Check your part number U3.

[swwww]

Re: Vizio vw37l Amber light only will not power on

u7 readings are as reported...

Correction on u3
az7805t

I'm not sure why your are saying it should be 1.25v at pin 2 All the rest of the 1117's are as reported pin 2- 3.36v when tested in the same way, same fixed regulator ( I am grounding meter to chassis ground) When grounding to the regulator ground leg The other 1117's give the 1.25 you are referring to (which is 2.1v different) with the exception of u7 which is as reported(w/meter ground on chassis).. there must be a 2.10v ground difference from chassis ground an the 1117's ground legs.

Could a u7 failure cause this ground potential difference or are the(1117's) supposed to run w/ ground leg 2.1v off chassis ground? (i am assuming what I am calling pin 1 is the ground leg)

strange how u7 pin 3 is 2.1v lower than the rest of the 117's pin 3s.

thanks for all your help



thanks

[retiredcaps]

Re: Vizio vw37l Amber light only will not power on

u7 readings are as reported...

I'm not sure why your are saying it should be 1.25v at pin 2

Have another read through the how to test a voltage regulator guide (especially post#1 and post#4).

[swwww]

Re: Vizio vw37l Amber light only will not power on

I reviewed it

did you read all my previous post....

[johnboy1313]

Re: Vizio vw37l Amber light only will not power on

looks like U7 has a 3.3V input where the others have a 5V input. Pin 2 of U7 should read right around 1.25V.

[tom66]

Re: Vizio vw37l Amber light only will not power on

Yes, output voltage (pin #2) = pin #1 voltage + 1.25V, as long as regulator has more than ~0.8V between desired output and input.

[swwww]

Re: Vizio vw37l Amber light only will not power on

Is it just coincidence that the input of u7 is 2.1 v lower than it should be ( which is the same voltage that the other similar 1117s ground legs are reading--2.1v....

And why would it be low.. Is that a u7 failure or a indication of associated circuitry failure.

Could u7 be shorting 2.1v of its input to ground causing the 2.1v on the other 1117's gound leg?

Or as asked in a previous post, is the ground leg supposed to be off zero on these 1117s...

thanks

[tom66]

Re: Vizio vw37l Amber light only will not power on

Is it just coincidence that the input of u7 is 2.1 v lower than it should be ( which is the same voltage that the other similar 1117s ground legs are reading--2.1v....

Yes. The regulator can be configured to output any voltage and this is determined by the voltage on that pin. All the main regulators put out 3.3V (2.1V + 1.25V), but there's also a 1.25V regulator (U7: 0V + 1.25V), and the failure is with that.

And why would it be low.. Is that a u7 failure or a indication of associated circuitry failure.

Nobody knows why Vizio have this problem so often, perhaps an instance of "sort by lowest price" on the manufacturer's catalogue, or by accidentally (or deliberately..) buying counterfeit parts. Also, they often run very hot due to being used near their maximum power rating. I have also encountered failed regulators on Samsung and Haier/Bush TVs.

Could u7 be shorting 2.1v of its input to ground causing the 2.1v on the other 1117's gound leg?

No, each regulator is independent.

Or as asked in a previous post, is the ground leg supposed to be off zero on these 1117s...

It can be any voltage you like. A 1117 can output anywhere from 1.25V to around 18V, depending on the requirements of the circuit different voltages are used.

Replacing U7 should be all that is necessary.

[budm]

Re: Vizio vw37l Amber light only will not power on

U7 gets the input voltage from the output of U33. U7 is bad.
As shown in post 6, U33 output is 3.36v, THE INPUT OF THE u7 IS 3.36V. If you check out the connection between the output of U33, it will be connected to U7 input pin. Pin 1 (ADJ/ or GND (for fixed regulator) and pin 2 (output pin) will ALWAYS BE 1.25V due to the 1.25V Vref of the regulator.
Pin 1 will be grounded for 1117 Fixed regulator, or will have voltage on pin 1 due to resistor network for setting the output voltage for the Adjustable 1117 series.

[swwww]

Re: Vizio vw37l Amber light only will not power on

Thank you much for all the info . I really appreciate you taking the time to help clear that up

Do you think that my assumption of why u-3(the 2nd of the largest two regulators, residing on the upper right corner of board)does not have power input is a correct one?

(see my first post) ( i am thinking this part of the board is not active while in standby or is it due to the failure upstream?)


thanks much

[tom66]

Re: Vizio vw37l Amber light only will not power on

Yes, that regulator is correctly functioning (as it receives essentially no input, it gives no output.)

[swwww]

Re: Vizio vw37l Amber light only will not power on

Ill give u7 a try and see what develops.


not sure i get what you mean

(as it receives essentially no input, it gives no output.) (u3)

so are you are saying no input should not be expected for the conditions ( because of tv not being on) or are you just stating the obvious (no input no output)



Also...

I do not have an air tool... Are the methods I have read regarding hot iron techniques (heating the tab/globing the legs, ect.) viable methods or does anyone have any good methods/links?

thanks

[tom66]

Re: Vizio vw37l Amber light only will not power on

The best way to get it off is not using hot air. Glob solder across the three main pins, then heat up the tab and those pins alternately. You'll shortly be able to push it off. This video describes it well.

https://www.youtube.com/watch?v=cNFzBJELFoU&t=8m40s

[budm]

Re: Vizio vw37l Amber light only will not power on

I use the same method as Tom, your iron should be 40watts or more with big tip.