VIZIO M552i-B2

[ca2014mp2]

Re: VIZIO M552i-B2

tv plugged in lcd panel connect:
HVDD, .8 mv
VCC, 3.327
VDD, 2.3mv
VGH, -202.4mv
VGL. -5.13
Look for shorted circuit on the tab bonding boards, I.E. capacitor, or COF.
You can first check the resistance between circuit GND and HVDD, VDD, VGH to see which one shows low resistance reading.

VDD is shorted and the short is removed when I disconnect the right hand ribbon. All other testing is good. Hvdd vgh are not shorted.

so following the short Im focused on the right hand tab bonding board and the caps are not the same as the left hand side. All the caps on the left tab bonding board are 35uf and on the right tab bonding board I have 5 and I'm getting that they have turned to wires not caps LOL.. the last cap at the far end of the display - the far right hand side is the only one with a reading of 22.49 uf.. I suspect that the short is pulling some of the others down but ill assume they are all bad for now and go for replacement.. the resistors are all good on that tab bonding board. I'll now try to isolate by pulling caps to find my short.. I'll update soon.

[budm]

Re: VIZIO M552i-B2

The T-CON could have been damaged trying to drive shorted circuit.

[budwich]

Re: VIZIO M552i-B2

oh things just got interesting: ok in reference to me facing the tv from the front:

I removed the tcon board's ribbon to the display right hand side and 3/4 of the right hand screen lit up very brightly and tappers off to the left see picture 1

Then I removed the tcon board's ribbon to the display left hand side and 3/4 of the right hand screen it up dimly in comparison to the first test and has the exact same pattern showing on the screen just dimmer. picture 2

The first picture is somewhat "normal" on the disconnected side (nice white). The bad news is the connected side shows vertical lines which should have been a display of what was being input or maybe blank / black.
The second picture with the opposite cabling shows no "nice white" for the now disconnected tcon to panel cable on that side. :-(

As you have found and probably confirmed with your measurements, there appears to be an issue with the bottom edge driver board on that side. It is not looking good but as budm suggests you might find a edg board component that is replaceable with care to fix the problem.

Further: since you have tried a second tcon, you can see the results are a bit different. The problem for the second card is that disconnecting right side no longer displays a white half screen. From this, I would think that this tcon card has a problem.... if you put back the first card, and repeat the "test" does the screen go back to the initial set of pictures?

[budm]

Re: VIZIO M552i-B2

tv plugged in lcd panel connect:
HVDD, .8 mv
VCC, 3.327
VDD, 2.3mv
VGH, -202.4mv
VGL. -5.13
Look for shorted circuit on the tab bonding boards, I.E. capacitor, or COF.
You can first check the resistance between circuit GND and HVDD, VDD, VGH to see which one shows low resistance reading.

[ca2014mp2]

Re: VIZIO M552i-B2

Check the Voltages on the T-CON without having the cables between T-CON and the LCD panel connected first.
Voltage test points around U2 (LCD power supplies): HVDD, VCC, VDD, VGH, VGL.
On the left side of the board: VEPI, VCORE.
Then do the same test with cables back in place.

tv plugged in lcd panel disconnected:
HVDD,7.87
VCC,3.325
VDD, 15.72
VGH, 28.19
VGL. 5.12

VEPI,1.813
VCORE.1.205

tv plugged in lcd panel connect:
HVDD, .8 mv
VCC, 3.327
VDD, 2.3mv
VGH, -202.4mv
VGL. -5.13

VEPI, 1.811
VCORE. 1.205 -- but drops to zero after 10 min during verification process.

all measurement are volt unless specified different

[ca2014mp2]

Re: VIZIO M552i-B2

I suggested the hdmi source just to see if the main board produced audio, Anything could be causing the issue on the main board, even a corrupt eeprom.
The osd and logo come from the main board, I'm not sure how you can track down the problem, You said you already replaced the t-con and that did'nt change anything so I would guess the fault is on the main board.

I have a scope to check for video signals on the main, lvds cable and t-con so I don't have to guess where the fault is located.

Ok, on this test I didn't see any osd but it was clear that my inputs from the remote where having an effect on the tv. Shades of back light were turning up and down in brightness. After playing with the input button and doing different combinations I was able to get a flicker, just a few vertical lines that quickly disappeared to just a white screen. And then the audio came in. It was nice and clear. so I've proved sound have half a white screen but no image.

[budm]

Re: VIZIO M552i-B2

Check the Voltages on the T-CON without having the cables between T-CON and the LCD panel connected first.
Voltage test points around U2 (LCD power supplies): HVDD, VCC, VDD, VGH, VGL.
On the left side of the board: VEPI, VCORE.
Then do the same test with cables back in place.

[ca2014mp2]

Re: VIZIO M552i-B2

I suggested the hdmi source just to see if the main board produced audio, Anything could be causing the issue on the main board, even a corrupt eeprom.
The osd and logo come from the main board, I'm not sure how you can track down the problem, You said you already replaced the t-con and that did'nt change anything so I would guess the fault is on the main board.

I have a scope to check for video signals on the main, lvds cable and t-con so I don't have to guess where the fault is located.

Well come on with those measurements and where you took them. I have two scopes here. I'm setting up for the HDMI test but it will be in 30 min.

[ca2014mp2]

Re: VIZIO M552i-B2

Tcon board front and back Hi-res

[R_J]

Re: VIZIO M552i-B2

I suggested the hdmi source just to see if the main board produced audio, Anything could be causing the issue on the main board, even a corrupt eeprom.
The osd and logo come from the main board, I'm not sure how you can track down the problem, You said you already replaced the t-con and that did'nt change anything so I would guess the fault is on the main board.

I have a scope to check for video signals on the main, lvds cable and t-con so I don't have to guess where the fault is located.

[budm]

Re: VIZIO M552i-B2

Can you please upload good clear hi-res pictures of the whole T-CON board? There should be a bunch of Voltage points that you can check.

[ca2014mp2]

Re: VIZIO M552i-B2

what about the osd or the Viszio logo on boot up. Is that generated from the MB? I can hook up a HDMI but with no image it wont prove anything. For this test are we thinking that the tcon and display are good? Or maybe a better question is what have we proven with this test?

[ca2014mp2]

Re: VIZIO M552i-B2

Well that is what i'm after, what test do you want to do to get us there?

[R_J]

Re: VIZIO M552i-B2

Sometimes if the panel has a problem, this test can show a picture on either half of the screen. since there is no real video, it could be a faulty main board, the issue of no audio could just be the tv is set to the wrong source, sometimes connecting a hdmi source will automatically switch to the correct input and then you might have sound.

[ca2014mp2]

Re: VIZIO M552i-B2

Ok fortunately I do have another tcon board with all references the same I swapped out the board.

From the second board round of test:
I removed the tcon board's ribbon to the display right hand side and 3/4 of the right hand screen lit up very brightly and tappers off to the left.

Then I removed the tcon board's ribbon to the display left hand side and 3/4 of the right hand screen it up dimly and darker than the first boards test in comparison to the first test and has the exact same pattern showing on the screen just dimmer much dimmer. see picture 2

ON either test I didn't hear sound or OSD just what is in the picture

[ca2014mp2]

Re: VIZIO M552i-B2

oh things just got interesting: ok in reference to me facing the tv from the front:

I removed the tcon board's ribbon to the display right hand side and 3/4 of the right hand screen lit up very brightly and tappers off to the left see picture 1

Then I removed the tcon board's ribbon to the display left hand side and 3/4 of the right hand screen it up dimly in comparison to the first test and has the exact same pattern showing on the screen just dimmer. picture 2

[ca2014mp2]

Re: VIZIO M552i-B2

6 resistors at 6 locations are not broken @ .6 to .7 ohms
My board pictured below

[R_J]

Re: VIZIO M552i-B2

Seems like the backlight is working, pressing menu has an effect on the backlight which would be expected as the backlight would be dim without any video.
Try disconnecting one of the cables between the panel and t-con, see if you get half picture, then reconnect and try disconnecting the other cable between panel and t-con.

Disconnect & reconnect cables with tv unplugged.

[tvtimmy]

Re: VIZIO M552i-B2

Check all the 000 resistors on the led driver board. I think I count 6.

[ca2014mp2]

Re: VIZIO M552i-B2

No, sorry I looked at that, it's fine.. and thanks.. any idea where I can get wiring diagrams?