Visio VO320E - black screen

[wenter]

Hi, all
I have a Visio VO320E TV that has no picture. When turned on Visio sigh in the front turns from yellow to white, but nothing else happens. I have read the forum and someone who was fixing his Visio pointed to specific components on the main board. I have located similar components on my board and took readings with power off/power on.

Here are the readings:
U2: 0.44V 0v 0v / 1.71V 0v -1.27
markings on component: L373 G1117

U7: 0V leg cut 0.43v / 1.27v leg cut 1.71v
markings on component: L323 G1084

U9: 0.43v 0v 0v / 2.5v 0v 1.27v
markings on component: L373 G1117

U11: 0v 0v 0v / 1.78v 0 0
markings MC 7805CT

I suspect that the linear voltage regulator U11 is not working.

Any ideas what may be wrong with the TV?

[TimT]

Re: Visio VO320E - black screen

have you checked the two fuses on the main board?

[TimT]

Re: Visio VO320E - black screen

disregard that. I had a similar issue. I ended up replacing a regulator U8 if I remember correctly.

[wenter]

Re: Visio VO320E - black screen

is that the U11 on my board?

[budm]

Re: Visio VO320E - black screen

Please report the readout again after reading this post in the format that we can easily under stand, it will be so much easier for us the figure out what you are getting on your reading.
Also the pictures of the back side of the TV so we can see how many boards and what kinds you have in your TV.
https://www.badcaps.net/forum/showthread.php?t=22231

[wenter]

Re: Visio VO320E - black screen

ADJ = Pin 1
Out = Pin 2
In = Pin3

U2
L373
p1: -1.27
p2: - 0.03
p3: 1.71

u8
L373
p1: -1.27
p2: - 0.03
P3: 1.99

U9
L373
p1: -1.27
p2: -0.03
p3: 2.51

U7
L323
p1: -1.27
p2: -0.03
p3: 1.71

U4
L373
p1: -1.27
p2: -0.03
p3: 1.75

U5
L373
p1: 2.41
p2: -0.03
p3: 1.7

U11
7805CT
pin 1 out: 0
pin2 ground: 0
pin 3 in: 1.71

[wenter]

Re: Visio VO320E - black screen

Here is a picture of the back of the TV.

[budm]

Re: Visio VO320E - black screen

Retiredcap format:
U100 -> pcb designation
AS1117-33 -> line 1 of the IC
0506 -> line 2 of the IC
pin 1 = 0.000
pin 2 = 3.301
pin 3 = 5.001

Sorry to ask, but the "L373" there are other number after that, I.E. 1117, OR 1117-33, ETC.
Result also does not look right at all:
Your results:

ADJ = Pin 1
Out = Pin 2
In = Pin3

U2
L373
p1: -1.27
p2: - 0.03
p3: 1.71

u8
L373
p1: -1.27
p2: - 0.03
P3: 1.99

U9
L373
p1: -1.27
p2: -0.03
p3: 2.51

U7
L323
p1: -1.27
p2: -0.03
p3: 1.71

U4
L373
p1: -1.27
p2: -0.03
p3: 1.75

U5
L373
p1: 2.41
p2: -0.03
p3: 1.7

If p2 is truly output, then just about all of them have no output.
1117 series regulator:
Notes: we are looking at the regulator with the Big tab up (the big tab is tied internally to the center pin).
Left pin (1) is ADJ/GND, Center pin (2) is Output, Right pin (3) is input.

From my post:
This is the way to figure out if the adjustable regulator is good or not:
Notes: we are looking at the regulator with the Big tab up (the big tab is tied internally to the center pin).
Adjustable regulator will have two resistors attached to it, one resistor (Rfb) is between pin1 and pin2, another resistor (Rg) is between pin1 and ground. Pin3 is an input pin.
The voltage between the Adjust pin (left pin) and the center pin (Pin2, output) will always be 1.25V +/- 2% (this is the precision voltage reference), if it is not, it is bad.
To figure out what the output voltage should be: measure the voltage between pin 1 and ground and add 1.25V to that number, that is the output voltage on pin 2 but you have to make sure you do have 1.25 between pin 1 and 2 as noted above.
You have one of those power supply-inverter board combo type.
I suspect that the main board is not sending the BL_ON signal to the PWR-INVRTR board.

[wenter]

Re: Visio VO320E - black screen

The regulator L373 has G1117 on the second row.
The regulator L323 has G1084 on the second row.

I am attaching the picture with marks how I assigned pin numbers.

[wenter]

Re: Visio VO320E - black screen

Pins numbers

[budm]

Re: Visio VO320E - black screen

OK, I see why you are getting the wrong readings, that big tab on the regulator is connected internally to the center pin of the IC, so the big is the same as Out pin.
You need to put the black probe of your meter to the metal chassis which is the Ground ref. point, then the red probe for reading In, Out, Adj.
So there is nothing printed on the body of the IC like 1117-18 (1.8V fixed regulator), 1117-33 (3.3V fixed regulator), etc.? Just 1117?
I am glad you show the picture how you made the measurement.

[wenter]

Re: Visio VO320E - black screen

U2 Adj to Center: 1.22v
U8 Adj to Center: 1.23v
U9 Adj to Center: 1.23v
U7 Adj to Center: 1.23v
U4 Adj to Center: 1.23v
U5 Adj to Center: 1.23v

I do not mind replacing all voltage regulators, I just need to know what parts to order.

[budm]

Re: Visio VO320E - black screen

In order to get the correct regulator, we need to know if they are fixed regulator or adjustable regulators, you may have both types.
So we still need the Voltage readings of the regulators to see what they are.

[wenter]

Re: Visio VO320E - black screen

Here are the readings: black probe on chassi, red on "out" center pin:
U2: 3.28v
U8: 1.23v
U9: 2.48v
U7: 3.29v
U4: 3.28v
U5: 2.60v
U11: 0 zero

[budm]

Re: Visio VO320E - black screen

OK, can you do the same report for the adjust pin and chassis? U11 is 78xx series regulator which rarely goes bad, inthis case, it is 7805 which is 5V regulator.

[wenter]

Re: Visio VO320E - black screen

It seems that U8, U9 and U5 are bad. I think they are 3.3v. I also think that the U11 5v 7805CT is bad as well.

[wenter]

Re: Visio VO320E - black screen

Here is Adj pin to chassi:
U2: 2.04v
U8: 0 v
U9: 1.24v
U7: 2.04v
U4: 2.04v
U5: 1.36v
U11: 0 zero

[budm]

Re: Visio VO320E - black screen

Well that is why I need the reading on ADJ and Ground because Adj to ground reading + 1.25 will be what the output voltage should be.
For example, are you getting 0V at U8 adj PIN? if you do, then the out put should then be 1.25V +/- 2%.

[wenter]

Re: Visio VO320E - black screen

yes, I am getting 0v on U8. Gnd to Adj. Gnd to Out 1.23v

[wenter]

Re: Visio VO320E - black screen

Can you recommend the part to replace U8? (I will buy few extra if I will need to replace U9 and U5)