Vizio M65-C1

[mrtek]

Hi.

picked up another TV. This time is a Vizio M65-C1. TV does not turn on. I had repaired another 60 inch vizio , Bad main board.
When power button is pressed, the Power led indicator on the bottom right, turns for a few seconds and then it fades away. No backlight or Vizio logo on screen. Removed back cover and repeated test.
This is the TV This TV is a little different from the Samsung I have worked on. Power supply is on the Left side, Main Bd is on the right side, T-CON , not in the picture is on the bottom. I am assuming that the boards in the middle are the LED Drivers. Why 2 boards and what is the function of each one?
When power cord is connected to PS board, one RED LED on main board turns on and stays on
. Checked voltages at power board and everything looks normal. I have +24V, +19V. The other connector going to main board has :
ON / OFF = .147V
Dim = 3.3V
PS _ON = 3.6V

When power button is pressed, a smaller Pink LED turns on next to the RED one and stays on until power button is pressed again. The power LED indicator turns on and fades away. When power button is turned OFF, the RED led stays on. No indication of LED turning on or Vizio LOGO on TV

Removed main board and check ed some capacitors under one of the main CPU and noticed that some them, measure between 7-10 ohms.
Removed all the capacitors in questions but small resistance value is still there. So, I am assuming that somehow the main board is defective and the fact that I read that small resistance value accross those capaitors is an indicator that either and internal short / has happened.
Wanted to be sure I am not missing anything before I order a new main board.

Thank you in advance for any suggestions.

Massimo

[howardc64]

Most common failure is cracked BGA solder balls on the main board BGA chips under the 2 depressed rectangles in the heat sink. Proper BGA removal and reflow is necessary for long term fix (over bake or hot air gun/dryer fix usually don't last long) And need to know enough about heating boards to not do more damage (cold garage floor on bottom and hot air on top will usually warp + crack something)

https://www.youtube.com/watch?v=XjB5vwSqDg0
https://www.google.com/search?q=m65-...t=gws-wiz-serp

On main board, not all low ohm caps are shorts. SOC CPUs need ~1v and operates in GHz speeds. So their voltage rail filtering caps to ground is super low resistance. Think of it this way, if you need to clock fast to GHz, need low resistance So if the caps are on low voltage rails (1v = CPUs/GPUs, 1.8v = DRAM, 3.3v = eMMC), its likely the correct design.

BTW, easy solution of just replacing the main board are often costly on these Vizios with similar shaped heat sinks. Its because so many fail and most people don't have access to proper BGA remove/reflow equipment like above video. So pricy due to low supply and high demand.

[EazyBone]

Yea id agree, likely a reflow of bgs chip. I have this exact TV same problem. Although I didn't watch the main board while reflow and it bent it and no longer works lol so oh well.

[lotas]

The board should heat up evenly over the entire surface, without bottom heating the board warps and becomes deformed and such a board cannot be repaired, since the BGA chip will no longer lie evenly on the surface of the board...

[EazyBone]

The board should heat up evenly over the entire surface, without bottom heating the board warps and becomes deformed and such a board cannot be repaired, since the BGA chip will no longer lie evenly on the surface of the board...

Yup figured this one out.

[mrtek]

Most common failure is cracked BGA solder balls on the main board BGA chips under the 2 depressed rectangles in the heat sink. Proper BGA removal and reflow is necessary for long term fix (over bake or hot air gun/dryer fix usually don't last long) And need to know enough about heating boards to not do more damage (cold garage floor on bottom and hot air on top will usually warp + crack something)

https://www.youtube.com/watch?v=XjB5vwSqDg0
https://www.google.com/search?q=m65-...t=gws-wiz-serp

On main board, not all low ohm caps are shorts. SOC CPUs need ~1v and operates in GHz speeds. So their voltage rail filtering caps to ground is super low resistance. Think of it this way, if you need to clock fast to GHz, need low resistance So if the caps are on low voltage rails (1v = CPUs/GPUs, 1.8v = DRAM, 3.3v = eMMC), its likely the correct design.

BTW, easy solution of just replacing the main board are often costly on these Vizios with similar shaped heat sinks. Its because so many fail and most people don't have access to proper BGA remove/reflow equipment like above video. So pricy due to low supply and high demand.

I know, I have researched these main boards and they go for $150 Some companies offer BGA reflow services but it looks like to me that my board has been worked on.
How hot these heat sink get? I have seen a guy placing a fan on top of the bga heat sink thru a cutout in the rear panel. He claimed it worked. I am sure it would help but for how long , is the question.

[howardc64]

I know, I have researched these main boards and they go for $150 Some companies offer BGA reflow services but it looks like to me that my board has been worked on.
How hot these heat sink get? I have seen a guy placing a fan on top of the bga heat sink thru a cutout in the rear panel. He claimed it worked. I am sure it would help but for how long , is the question.

A lot of variables. Google BGA ball cracking to see microscope pics of the fracture. If just remelt, the cracks oxidize so will recrack easily. If prior incorrectly heated, then warp might have occurred and if bga doesn’t sit perfectly flat, the solder ball soldering will be uneven across the chip.

anyway no way to know. Best is proper bga removal / reball / reflow.