Visio Main Board Repair

[gustav]

I was curious on the success rate of repairing the Visio's Main Board issues and what was done to correct the problem. There are a lot of detailed threads on troubleshooting, but most of them just replaced the board. Apparently this is a recurring issue with the Visio's. One member said that 90% of the Visio's he encountered were the main board. It also appears to be the voltage regulators are the culprits, but various other components can very well be faulty. Any thoughts?

[newtothis]

Anything near enough is repairable with the Time, Money and tools (oh and experience)... but is it cost effective is the question?

Throw some pics at us, tell us whats happening and get your DMM out

[gustav]

Haven't had a chance to check anything yet. It's at another location for the time being. Will get hands on it tomorrow. Been reading pages and pages of threads on here that has pointed in that direction. Just wondering on how many people had success repairing the boards at the component level compared to the ones who simply replaced the board.

[johnboy1313]

I've fixed 15 Vizio's in the last year. 7 of them (47%) had a fault on the main board. Of those seven, 4 had bad voltage regulators, 2 had blown surface mount fuses, and one had a bad EEPROM.

[ibgm]

I grabbed a Vizio at my local dump, I had to replace the voltage regulators. When I was done, I found that the HDMI inputs didn't work, so I used the Composite Video jacks and that's good enough for my bedroom. It definitly was worth the cost of the regulators. Maybe some day I'll figure out the HDMI issue, but for now, it works....

[gustav]

The only thing I know is the power button turns amber to white with no picture not sure on sound. Maybe that's a good place to start. I read where the power button color changes, blinks, etc can indicate a certain fault.

[johnboy1313]

What's the model number?

[budm]

Model number of the TV and pictures of the boards will help. If the VIZIO does run white but no backlights, then you need to look at the BL_ON (INVR_ON) to see if the main board is sending the control signal or not.

[gustav]

The model number is XVT472sv. I will post pics and readings as soon as I can get the set here, looking at later on tonight.

[gustav]

The insignia turned white and no picture. Popped the cover and did a visual: caps looked good, no visible sign of damage or burn marks. Fuses checked out.

While doing a visual, the t.v. made that clicking tripping sound, by itself, like it was just turned on, and with a long delay about 30 secs or so, the panel lit up! Then after 10 minutes it died. The readings off the power supply connector:

5V standby= 5.5
12V = 7.4
PS_ON = 1.58
24V = .650

Main-board voltage regulators:

1117 type
U2: Input: 5.08 Output: 3.31 Adj: 2.05
U4 Input: 3.29 Output: 1.25 Adj: 1.1
U6: Input: 6.00 Output: .20 Adj: 1.8
U7: Input: 5.04 Output: 3.3 Adj: 2.07

Yes, I checked three times on U6 will use another MM later

L373 G1084 type:

U3 Input: 5.04 Output: 3.3 Ground: 2.05
U5 Input: 5.05 Output: 3.3 Ground 2.05

Mainboard Number: 3647-0282-0150(6b)

There it is.
I'll continue to check tomorrow.

[budm]

"1117 type
U2: Input: 5.08 Output: 3.31 Adj: 2.05
U4 Input: 3.29 Output: 1.25 Adj: 1.1
U6: Input: 6.00 Output: .20 Adj: 1.8
U7: Input: 5.04 Output: 3.3 Adj: 2.07"
OK, you can tell of the ADJ 1117 is good or bad by adding 1.25V which is the internal Vref to what you read on the ADJ pin, that number is what the output voltage should be. I.E. U6, adj is 1.8V, so the output (center pin) should be = 1.25 +1.8 = 3.05V.
You may want to recheck the readings again.
Right now the main power supply (12V/24V) is not working.

"The insignia turned white and no picture" is it Insignia or Vizio? this thread is related to VIZIO.

[gustav]

The VIZIO insignia. My bad. The U6 I just checked it is input: 6.9 output: 1.87 (middle pin) I would say U6 is bad. Most likely it needs to be replaced. and a good idea to replace the others. Thanks for the vref formula. I was wondering about that. I guess U4 should be around 2.35 adj: 1.1+1.25. U7 looks within range.

[cliff_hootarski]

Vizio Logo?

[johnboy1313]

Insignia, logo, same thing.

[budm]

U4, U6 are bad.

[gustav]

ordered from Mousers 5 of the 1117's. Hopefully, they will be here Sat or Monday. They seem to get here faster than Digikey at the economy rate. Don't know why, but they do. Is there something else I should be testing while waiting for the LDO's?

[budm]

You can check the power supply to make sure the 12V/24V powerr supply section is OK by using 1K between PS_ON pin and the 5VSTBY pin, but you have to remove the wire that is connected to the PS_ON pin that goes to the main board otherwise the voltage on PS_ON pin will not be able to go HIGH since the main board will keeps it LOW.

[gustav]

Update: Replaced u4 and u6. Tv still not clicking or powering on. I am getting about 60v on the primary heat shield on the power supply. I was shocked by it. Hmm. I'll try to check the PS_on and stby thing first and then check voltages on the power supply as well as check voltages on the replaced LDO's. Ugh.

I wanted to pass this on too. The easiest way to remove those voltage regulators I found was Bud's trick of cutting the legs. I didn't have any cutters around, so a pair of toe-nail clippers did very well. Then I wiggled the IC around to loosen the back large pin.
This way it avoided accidental touching of any caps or the small smd's around the Voltage regualtors, i.e., pin head size resistors around the adjustable pin with the soldering iron. It also opened up the space allowing easy removal of the remaining back pin. Of course, this was a trial and error experience.

So, back to the basics.

[gustav]

Jumped the pson and stby. im getting 24v.

[gustav]

Also, the 12v fuse now is showing 12.2 as well as U8 voltage, whenever the stdby and ps-on is jumped. The 12v 18v and 24v are showing on the p.s. connector. The voltage on the p.s. heat shield was due to the fact the dmm was set to ac and not dc. So, that's out. It appears to be the mainboard. But cannot figure out was is the cause. V.R.s seem to check out. A guess is the Main I.C. is the culprit. It might best to buy another main board. There are 3 new VR #1117 maybe go ahead and switch out the other two, but they seem to be within spec. Any ideas would be appreciated.

Thanks again