Vizio E321VL

[killian6pk]

Re: Vizio E321VL

OK, you do not have the PS_ON signal from the main baord when you trun on the TV, that is why the PFC and the 12/24 Vdc power supply do not turn on. So we need to find out where the fault is on the main board.

Last night when I checked the PS-On voltage and found none I went over to the mainboard and checked the 3 AP117 Regulators that everyone seems to find bad. From reading all the threads on Vizio Tv's this seems to be a common issue. I am not sure what I should be finding for readings on these regulators. I just checked them again, Pins are left to right with top bar oriented at top for reading purposes. Readings did not changed when I pushed the power button.
U4 = 2.05 3.29 OF
U5 = 0.55 1.79 3.32
U6 = 0.0 1.24 3.32

[killian6pk]

Re: Vizio E321VL

Maybe re check pson test as in
https://www.badcaps.net/forum/showpo...2&postcount=26

Based on this I retested the PS-On using the common (black) on ground screw by AC in and red on #11 pin and got zero volts. While pushing the on/off button I still got zero volts. If I was testing correctly then the problem seems to lie with the Main Board. Since I was getting some power through to the AP117 regulators (see reply to Buds message) then they might be the problem.

[selldoor]

Re: Vizio E321VL

On the 1117s what are the part numbers if they are fixed voltage then they usually say xx1117-33 xx1117-18 etc.
Early on you did say you had changed all the caps did that include the small start up cap ( Not being cheeky -but is it the right way round)
Have you had chance to check out the possible trace faults?

[killian6pk]

Re: Vizio E321VL

On the 1117s what are the part numbers if they are fixed voltage then they usually say xx1117-33 xx1117-18 etc.
Early on you did say you had changed all the caps did that include the small start up cap ( Not being cheeky -but is it the right way round)
Have you had chance to check out the possible trace faults?

They just have a 1117 on the markings. I am going by the other threads that I have read that they are Adjustable 1 amp 5V Sot223. Some of the larger tv's have 5 of these mine just has 3. I rechecked all of the Caps yesterday and they are all in correctly. I am going to try chasing down the traces in a few minutes. Should I start at the connector to the Main Board and work backward along the traces starting with the PS-On pin?

[budm]

Re: Vizio E321VL

You can easily tell if these 1117 are FIXED output or Adjustable out put or by looking at pin 1 (left most), if it is tied to ground, then it is fixed output, it has two resistors (one resistor from pin 1 to ground and another resistor between pin 1 and pin 2) then it is adjustable regulator. You can calculate the output voltage by using the formula as shown in the spec sheet.
On the adjustable regulator, the voltage between pin 1 and pin 2 should always be 1.25V (this is the ref voltage).

[selldoor]

Re: Vizio E321VL

"I am going to try chasing down the traces in a few minutes. Should I start at the connector to the Main Board and work backward along the traces starting with the PS-On pin?"

I was just meaning check the two that I thought looked broken
in the "traces" picture. Just go to the next solder joint on each side of the break and measure the resistance - should be nil.
You can then visually check for more breaks - magnifying glass?.
Wait and see what ideas Budm has for testing the main board.

[killian6pk]

Re: Vizio E321VL

You can easily tell if these 1117 are FIXED output or Adjustable out put or by looking at pin 1 (left most), if it is tied to ground, then it is fixed output, it has two resistors (one resistor from pin 1 to ground and another resistor between pin 1 and pin 2) then it is adjustable regulator. You can calculate the output voltage by using the formula as shown in the spec sheet.
On the adjustable regulator, the voltage between pin 1 and pin 2 should always be 1.25V (this is the ref voltage).

I just checked the voltage for all three between pins 1 & 2 and each are 1.24 or 1.249. Should I be checking these from pin 1 to pin 2 then pin 1 to pin 3 and then pin 2 to pin 3? Also there are two smd resistors under pin 1.

[budm]

Re: Vizio E321VL

Check the resistance from pin 1 and ground, it should be 0 Ohm if it is fixed output voltage regulator.

[killian6pk]

Re: Vizio E321VL

Check the resistance from pin 1 and ground, it should be 0 Ohm if it is fixed output voltage regulator.

U6 has 5.6ohms on pin one the other two show OF on pin one.

[killian6pk]

Re: Vizio E321VL

"I am going to try chasing down the traces in a few minutes. Should I start at the connector to the Main Board and work backward along the traces starting with the PS-On pin?"

I was just meaning check the two that I thought looked broken
in the "traces" picture. Just go to the next solder joint on each side of the break and measure the resistance - should be nil.
You can then visually check for more breaks - magnifying glass?.
Wait and see what ideas Budm has for testing the main board.

Ii checked those two traces and both were good.

[budm]

Re: Vizio E321VL

Not sure what you are seeing at pin 1 of U6, it looks (post #61) like it is fixed out put regulator with 3.3V input (pin3) and output (pin2) is 1.25V, pin 1 is ground (0v)

[killian6pk]

Re: Vizio E321VL

Not sure what you are seeing at pin 1 of U6, it looks (post #61) like it is fixed out put regulator with 3.3V input (pin3) and output (pin2) is 1.25V, pin 1 is ground (0v)

In post 65 I think you said, if it had two resistors that it was adjustable. U6 has 2 resistors stacked under pin 1. The other two have One under pin 1 and one between pin 1 and pin 2, but end to end.

I just took a look at U6 actually it is U8 my eyes are not great so I was wrong about the number, but under pin 1 it is printed on the board as (Adj.) under pin 2 it is (Out) and under pin 3 it says (In). Now the other two regulators: U5 says the same thing, but U4 does not have any of that printed on the board. So it looks like U8 and U5 are adjustable and U4 is not. I am going to try and take this board outside tomorrow and get a close up of each of these regulators and the arrangement of the resistors under them.

[budm]

Re: Vizio E321VL

If there is resistor to ground at pin1 of U6, then you should be able to read the voltage drop across that resistor unless you did not set the meter to the lower voltage scale so it can show better resolution.

[killian6pk]

Re: Vizio E321VL

If there is resistor to ground at pin1 of U6, then you should be able to read the voltage drop across that resistor unless you did not set the meter to the lower voltage scale so it can show better resolution.

If I read it correctly then I got 1.239v across the resistor under pin 1. I am attaching photos of the top of the Main Board taken this morning. On U4 I got the same as U8 and on U5 I got 0.546v

I also rechecked the regulators and none of the three have a number like 1117-XX so how can I tell what the nonadjustable regulator should be.

[killian6pk]

Re: Vizio E321VL

I guess I just answered my own question from post #74. You use the same regulator it is just connected to ground on the 1st leg. So the U4 regulator will not be adjustable because it is not wired to be.

[selldoor]

Re: Vizio E321VL

Is this ok or as it got a hole in it?

[killian6pk]

Re: Vizio E321VL

Is this ok or as it got a hole in it?

It looks to me like a ink stain. I can see a letter U under the whatever it is. It is not a hole for sure.

On my post, I think is #74 am I correct in what I am saying that the regulator is the same it is just what pin 1 is connected to that determines if it is fixed or adjustable. Fixed is connected to ground, Adjustable to a voltage source.

[budm]

Re: Vizio E321VL

Did you read the spec sheet of the 1117 I attached in the earlier post, it will explain everything.

[killian6pk]

Re: Vizio E321VL

Did you read the spec sheet of the 1117 I attached in the earlier post, it will explain everything.

If I understand what the data sheet is showing then pin 3 must always be 1.3V higher than pin 2.
On my regulators U4 is 1.94v higher, U5 is 1.53v higher and U8 is 2.08v higher so all three regulators are higher than spec. Does that make them bad or just better than spec.? Also U4 is the LDO (nonadjustable) regulator and pin 1 should be going to ground which should register 0v if I am thinking properly and is showing 2.05v.

[budm]

Re: Vizio E321VL

The minimum voltage difference between pin 3 (input pin) and pin 2 (output pin) needs to be at least 1.3V for the regulator to regulate, for example, if you want to have 2.5V output, the input voltage must be at least 3.8V if it is less than that, the output will not be able to maintain 2.5V output. This is applied to both Fixed and Adjustable.
The adjustable regulator, the voltage between pin 1 (adj pin) and the output pin 2 will always be 1.25 (this 1.25V precision voltage reference is inside the IC). For example, if you have adjustable regulator with the resistors between pin 1 and ground, and second resistor between pin1 and pin2 to set the out put voltage to be at 3.5V. The voltage reading between pin 1 and pin 2 must always be 1.25V (if the precision ref voltage circuit is working), then the voltage reading between pin 1 and ground should be = 3.5 - 1.25 = 2.25V. At the same time, the input voltage has to be at least 3.5 + 1.3V = 4.8V minimum.

The fixed regulator has the resistor network inside the IC, so you can only verify the input and out voltages only, you cannot get access to the 1.25V precision voltage reference circuits inside.