Vizio VO42L question

[tibimakai]

I'm working on this Vizio and I'm puzzled that what it's wrong with it.
Usually the slave inverter it's the problem, but this time the 8.5K values at the fet transistors were there and the chip looked OK. One of the caps was bulged, which I have replaced.
I have found a low value on one of the fet transistors on the master inverter(even after removal).
Replaced the fet and the value it was still low, it got a bit higher, but it was still very low(76 ohm), so I have replaced the chip and it became 8.5K.
I have done the bulb test on the power supply and check out OK.
The voltages are there and still no sign of back light(at least).
The blue LED comes on for like three seconds on the master inverter board, the Vizio logo works as it should, with the buttons.
What else can I check?

[tibimakai]

Re: Vizio VO42L question

I have measured the 2 big capacitors on both inverter boards in circuit and all of them show E=0.00 and respectively C=2650(most likely they are in parallel, they are 680uf) on the ESR meter.
One of them it's a new capacitor and that one shows E=0.00.

[retiredcaps]

Re: Vizio VO42L question

As usual, a picture of your boards would help.

[retiredcaps]

Re: Vizio VO42L question

What else can I check?

1) Does BL_ON or equivalent go to > 3V DC and stay there?

2) Did you check all the voltage regulators on the main board?

[tibimakai]

Re: Vizio VO42L question

The 3.3V is there as all the other voltages on the power supply.
The TV can be turned on and off, there is no problem there, in fact the TV acts as everything it's OK. But there is no sign of life from the panel.
Vizio logo turns white or orange if I turn it off.
The voltages are there, the blue LED turns on and then off on the master inverter.
I'm trying to see a picture with a flash light, but I can't see any.
Usually on these TVs the slave board has issues, but this time I had problem on the master inverter.
How can I check if the BD ICs on the inverters are working?
I have replaced the master IC since after replacing a shorted FET it was still reading very low.
Now all the FETs on both boards are showing 8.49-8.51 KOHM.
After checking with a lupe my soldering job, I have found a leg not soldered to the PCB tab. Do you think that it's possible that the IC it's not working properly because of this?
Another question, how do I know if the slave IC it's working properly or not?
Do you think that it's worth checking the regulators on the mainboard since the TV turns off properly?

[retiredcaps]

Re: Vizio VO42L question

After checking with a lupe my soldering job, I have found a leg not soldered to the PCB tab. Do you think that it's possible that the IC it's not working properly because of this?

Fix your soldering first and retest.

Do you think that it's worth checking the regulators on the mainboard since the TV turns off properly?

For Vizio TVs in general, regardless of age, I think it is mandatory to check all the regulators on the main board. About 75% of the problems with Vizios comes down to those components. It only takes 5 minutes to rule them out so why not?

[tibimakai]

Re: Vizio VO42L question

The IC it's soldered now, but it's no change. What I meant is the IC can't be damaged because one pin wasn't soldered?
I will check all the regulators tomorrow, and I will let you know.

[tibimakai]

Re: Vizio VO42L question

Something went wrong, but not sure what happened.
I had a bit of time to check the regulators on the mainboard and this time the TV did not turn on anymore.
There is no PS_ON, 12V or 24V with everything connected.
If I test the PS, it's all good, but it seems that I have a problem with the PS_ON voltage.
I have found only one regulator (if I remember correctly is the U22)with 5.2V, 3.3V and 2.09V.
Not sure what happened.
I will have to take much better pictures.

[tibimakai]

Re: Vizio VO42L question

Not sure what happened, but it is back in the same stage as before, after removing the mainboard for taking pictures.
I have all the voltages at the PS connectors. The blue LED comes on on the master inverter board and the Vizio logo turns white or turns orange when turned off.
I have checked all the regulators and here are the voltages.
U16: 11.84V/0.00V/5.02V
U44: 11.84V/9.59V/8.35V
U22: 5.12V/3.35V/2.10V
U17: 5.07V/3.36V/2.10V
U21: 2.54V/1.16V/0.00V
U??: 5.07V/2.54V/1.27V
U20: 3.30V/1.81V/0.56V

STBY: 5.52V
PSON: 3.30V
A: 2.58V
B: 5.07V
12V: 11.88V
24V: 25.05V

Next I will be uploading the pictures.
I have a question until then, how do I know if the BD9897FS are OK?
If the FET transistors have the 8.5Kohm, then they should be OK?
I have received the shipment from Digikey, so I will be replacing the four capacitors on the inverter boards.

[tibimakai]

Re: Vizio VO42L question

Replaced the inverter capacitors and still no change.
Here is the mainboard picture:

[retiredcaps]

Re: Vizio VO42L question

U21: 2.54V/1.16V/0.00V

I think U21 is bad. If the top tab is "up" or north, it looks like you are numbering the pins right to left.

From your pic, it looks like the part number is AMC1117 which is an adjustable voltage regulator. I just wrote about this, again, 2 minutes ago, so I will cut & paste from

https://www.badcaps.net/forum/showpo...7&postcount=50

The correct output for pin 2 (middle) is based on this calculation:

DC V of pin 1 + 1.25V = output of pin 2.

So 0 + 1.25 should be the "correct" output. You have 1.16V. Most specifications for regulators are +/- 1%.

At 1.16, it is (1.25-1.16)/1.25 = 7.2% out of spec (see post #6 last paragraph).

The same above URL gives a replacement part number.

[retiredcaps]

Re: Vizio VO42L question

PS. There is little to NO chance that your brand new Fluke 87V is incorrect either when measuring U21.

It is 0.05% DC V accuracy +1 count.

For fun, you can put it into 20,000 count mode by holding down the backlight button for 2 seconds and then retake the reading on pin 2.

It should give you 5 digits. Something like

1.1632

[tibimakai]

Re: Vizio VO42L question

Thank you, I will check it tomorrow.

[tibimakai]

Re: Vizio VO42L question

I'm an idiot, I have re-checked my notes and it's 1.26V, so it's OK.
How do I know if the inverter ICs are OK or not? The FET transistors have the right 8.5Kohm. But you are right that it's very possible to have something on the mainboard also. I should see something on the screen if only the inverters would be the problem.

[tibimakai]

Re: Vizio VO42L question

So any input?
Should I replace the IC on the slave board?

[retiredcaps]

Re: Vizio VO42L question

You can try to replace the IC. The voltage regulators all look good now that you provided the correct info.

[tibimakai]

Re: Vizio VO42L question

I should see a picture with the flashlight?

[retiredcaps]

Re: Vizio VO42L question

I should see a picture with the flashlight?

Some members see a picture, others don't. It might depend on the screen, type of glass, flashlight lumens, etc.

[tibimakai]

Re: Vizio VO42L question

I have replaced the IC on the slave inverter and there is no change.
Panel seems dead.
How do I know that the inverters are working?

[retiredcaps]

Re: Vizio VO42L question

How do I know that the inverters are working?

I guess you can measure the voltage on the FETs and see if there is any voltage on the Gate, Drain and Source.