Vizio VO37L power problem

[ronm6962]

I am trying to revive a Vizio VO37L TV, and making very little progress. I have read through several threads with similar symptoms and suspect the solution is there somewhere, but I need help with some diagnostics. Here are the symptoms and the diagnosis I have tried thus far…..
•When the power cord is plugged in, the VIZIO light at the bottom of the frame turns bright amber, then fades for a few seconds to about half the brightness, and stays amber.
•The screen is totally black, no light at all, and pressing the power button has no effect on the screen or the VIZIO light…it stays amber. (I do not have the remote control)
•I visually checked all the capacitors on all three boards, and could see no evident damage. After reading several threads, I I learned to check voltages at various points and here is what I have determined so far….
•The Power Supply board shows 5v at the 5VSB pins on connector CN3. It does not show voltage at the 12v pins. Voltage is also missing at the 24v pins of connector CN4.
•Therefore, it would appear the Power Supply board is failing, however I learned it has to be triggered by the Main board to turn on the 12v and 24v power.
•So I jumpered a 5v pin on connector CN3 to the PSON pin on CN3, and then I get 12v and 24v power on the respective pins of CN3 and CN4. Unfortunately, I still get no light on the screen and the VIZIO light remains amber.

There are likely other voltages that could be checked to further isolate the problem…at least to determine which of the three boards may be failing, so any advice is appreciated. Attached are pictures of the three boards…..Main board, Power Supply board, and Inverter board.

[budm]

Re: Vizio VO37L power problem

You need to check the voltages on those 3-pin Voltage regultors on the main board. Please read this thread and report the readings in the format we require.
https://www.badcaps.net/forum/showth...063#post491063

[ronm6962]

Re: Vizio VO37L power problem

Thanks for the reply, budm....I was hoping to get you as I see you have helped numerous others in this area. I need to confirm something before getting started, to assure I don't waste your time. Since I am not getting output from the 12v and 24v pins on the Mainboard connector J1, should I expect voltage readings on the voltage regulators? Also, here is one set of readings for U16....is this what you are looking for before I do all the others? Thanks.

U16 - Main Board
AZ7805T - line 1
748D11 - line 2
pin1 - 0v
pin2 - 0v
pin3 - 0v

[budm]

Re: Vizio VO37L power problem

You will not be getting the reading on that 7805 5 Volt regulator until the power supply gets the PS_ON from the main board to provide 12V/24V output to feed the main board, so at this point there is no need to worry about the 7805 yet.

[ronm6962]

Re: Vizio VO37L power problem

OK, thanks. I will continue checking and get back to you a little later. Thanks so much...I look forward to making some progress with this issue.

[ronm6962]

Re: Vizio VO37L power problem

Here are the voltage measurements requested. I think I got them all, but please advise if you think I missed anything.
U15
AMC1117
F0748F
In – 0v
Out - .05
Gnd - .03

U16
AZ7805T
748D11
In – 0v
Out – 0v
Gnd – 0v

U17
AMC1117
F0748F
Pin1 - .08v (left to right)
Pin2 - .13v
Pin3 – 0v

U19
AMC1117
F0748F
In – 0v
Out – 0v
Gnd – 0v

U20
AMC1117
F0748F
In - .05v
Out – 0v
Gnd – 0v

U21
AMC1117
F0748F
Pin1 – 0v (left to right)
Pin2 - .10v
Pin3 – 0v

U22
AMC1117
F0748F
Pin1 – 2.08v (left to right)
Pin2 – 3.33v
Pin3 – 5.12v


U44
AMC1117
F0748F
Pin1 – 0v (left to right)
Pin2 - 0v
Pin3 – 0v

[budm]

Re: Vizio VO37L power problem

Are you sure you are making good contacts with the legs of the regulators? only U22 has the input Voltage (5V.12V). Hard to believe that others 1117 have 0V input.

[ronm6962]

Re: Vizio VO37L power problem

Yes, I thought that looked odd as well...especially U15 that shows 0v in and .05v out. I will run the checks again. BTW.....should I jumper the 5v pin to the PSON pin on the Power Supply board and check that way as well?

[ronm6962]

Re: Vizio VO37L power problem

OK, did the checks again and made sure the probes were tight on the legs of the regulators....exact same measurements.

[budm]

Re: Vizio VO37L power problem

OK, I will have to look at SJ picture to see if there are more than two fuses on the board.
http://www.shopjimmy.com/media/catal.../0/2/026_3.JPG
SJ provided the picture.

[budm]

Re: Vizio VO37L power problem

OK, look at this thread and write down all the IC numbers (I.E. U22) that shows input voltage of 5V or so then you will know that those ICs Input pins are connected together, then use the Ohm meter to verify the ICs on your board to verify that they do have the input pins tied together, the resistance should be around 1 ohm or so.
Your board may have open circuit some where and that is why they are not getting the Voltage to the input pin.

https://www.badcaps.net/forum/showth...highlight=VO37
His voltage readings:
U21
L072 G1117
1. 0.0
2. 1.25
3. 2.5
this one seems good

U19
L072 G1117
1. 1.25
2. 2.5
3. 5.0
good

U17
L072 G1117
1. 2.08
2. 3.31
3. 5.03
2.08+1.25=3.33 which is close enough to 3.31 so this ones good?

U22
L072 G1117
1. 2.05
2. 3.29
3. 5.08

U44 (this one reads all 0 now since the accident)
L061 G9117
1. 8.32
2. 9.57
3. 12.0

U15
1084 0851PL
1. 2.06
2. 3.3
3. 5.02
(i noticed this middle pin doesnt actually seem to be connected to the motherboard but both the pin and the trace on the motherboard read 3.3.. .whats that about? the other 0851PL is the same way)

U20
1084 0851PL
1. 0.55
2. 1.79
3. 3.27

U16 - AZ7805T (this one reads all 0 now since the accident)
1. 12
2. i dunno cause i blew the fuse right here
3. dangit!

[ronm6962]

Re: Vizio VO37L power problem

OK, I'm a bit confused. AI "think" you want me to compare my IC #'s to the IC #'s in the list you included, then check continuity between pin3 on all the IC's on my board that match the ones on the list showing around 5v. Is that correct?

[ronm6962]

Re: Vizio VO37L power problem

Not sure if this is what you wanted, but here goes....
Pin3 from U15 to U17 to U19 all appear to be common, no resistance.
Pin3 from U15 to U22 starts with 1 ohm and then increases as though resistance is increasing. ???

[ronm6962]

Re: Vizio VO37L power problem

Probably staying up too late with this, so will ask one more question and check back tomorrow. Since Pin3 on VRs U15, U17, and U19 are common and show no voltage, and U22 does show 5v, would it prove anything if I jumpered 5v to pin3 of U15? Or is that more likely to cause problems? I'm trying to verify the backlight works on the screen. Just curious....will check in again tomorrow. Thanks for your help tonight.

[budm]

Re: Vizio VO37L power problem

I would not do anything until you probe out the connection first.

[ronm6962]

Re: Vizio VO37L power problem

OK, I'm back at it this morning. Please advise what I should do next. As noted above, it appears Pin3 is common among the U15, U17, and U19 regulators, but there is varying resistance on the U22 regulator. Thanks.

[ronm6962]

Re: Vizio VO37L power problem

Sorry, had to run an errand....back now.

[budm]

Re: Vizio VO37L power problem

Check the resistance between U15, 17, 19 input pins to see they all have low resistance (<1 Ohm) between all 3 devices, that will prove to us that those 3 devices are supplied by the same 5V supply.

[budm]

Re: Vizio VO37L power problem

I look at the pictures, I can only see 7 regulators, your list has 8 (U15, 16, 17, 19, 20, 21, 22, 44) total. I cannot read the U# from the pictures. Can you please tell me what those U # are? I marked them as 1~7, so please tell me what they are as shown in the picture.
I also need pictures in sections so I can clearly see the traces and prints on the board.

[ronm6962]

Re: Vizio VO37L power problem

There is zero resistance between the input pins of U15, U17, and U19. However, U22 has resistance that starts out low and gradually increases to several (10+) ohms. ???

I will work on some better pictures and get back later. My board is identical to your picture and the VRs are located as follows on your picture:
#1 - U20
#2 - U15
#3 - U17
#4 - U21
#5 - U19
#6 - U44
#7 - U16
#8 - U22 (hidden by a couple of bent caps, just to the right of #3 U17 on your pic)