M421VT LED Screen Color Distortion

[dfang]

Re: M421VT LED Screen Color Distortion

What I expected to see, Reconnect main and make sure we are at the original fault.

Well,,,we are not back to original fault because something happened between then and now..After my heat/cool procedure I lost the display all together..
With the main board connected,,the only voltage is the two 5.2vdc pins...no 24v and no 12v at PS connector..
Btw,,I reinstalled the shield on the main..

[newtothis]

Re: M421VT LED Screen Color Distortion

Best guess is the heat took out the poor BGA connection.

It is either attempt to reflow the BGA device or get a new main. With PSU jumpered it gives you the 12v, You won't see the 24v as the PSU wouldn't getting a signal to turn on the backlights. The main being faulty stops you getting the 12v as its not switching the PSU on.

Want to attempt a reflow?

Going to need flux and heatgun (tho if you have a HA station it would be preferable)

[dfang]

Re: M421VT LED Screen Color Distortion

Best guess is the heat took out the poor BGA connection.

It is either attempt to reflow the BGA device or get a new main. With PSU jumpered it gives you the 12v, You won't see the 24v as the PSU wouldn't getting a signal to turn on the backlights. The main being faulty stops you getting the 12v as its not switching the PSU on.

Want to attempt a reflow?

Going to need flux and heatgun (tho if you have a HA station it would be preferable)

I've got paste tinning flux and heat gun..

[newtothis]

Re: M421VT LED Screen Color Distortion

Needs to be a no clean flux, otherwise it will eat the connections over time

[dfang]

Re: M421VT LED Screen Color Distortion

Needs to be a no clean flux, otherwise it will eat the connections over time

Ok,,I'll have to get some next week..
Thanks NTT...

[newtothis]

Re: M421VT LED Screen Color Distortion

Remember this is no sure fire method of 100% reliability of working though, I use proper equipment for BGA work and I tell people not to try repairs on boards without it as a rule... But... as you won't have £1000 worth of equipment just to fix this board you may aswell try, If it doesn't work you are at square one still anyway and will need a new board, If it does work awesome you have your TV back

[dfang]

Re: M421VT LED Screen Color Distortion

Remember this is no sure fire method of 100% reliability of working though, I use proper equipment for BGA work and I tell people not to try repairs on boards without it as a rule... But... as you won't have £1000 worth of equipment just to fix this board you may aswell try, If it doesn't work you are at square one still anyway and will need a new board, If it does work awesome you have your TV back

Ah Ha...well,,I'm a gambler,,so,,no problem..What exactly does BGA look like on main board ? Btw I have reflowed computer Nvidia graphics cards before with mixed results..

[newtothis]

Re: M421VT LED Screen Color Distortion

Same principle as a GPU.

BGA stands for Ball Grid Array... Just the way they are soldered... You know its a BGA as you can't see any solder leads.

[dfang]

Re: M421VT LED Screen Color Distortion

Same principle as a GPU.

BGA stands for Ball Grid Array... Just the way they are soldered... You know its a BGA as you can't see any solder leads.

Does heat shield need to come off ? Please say NO..

[newtothis]

Re: M421VT LED Screen Color Distortion

Does heat shield need to come off ? Please say NO..

HeHe... yes

[dfang]

Re: M421VT LED Screen Color Distortion

HeHe... yes

Grrrr! Well,,I am a expert at that..

[dfang]

Re: M421VT LED Screen Color Distortion

Ok NTT,,got some flux,,,what is your recommended procedure for doing the Ball Grind flow with the equipment I have ? Do I need to remove heat sink ? Do I need to protect other components with aluminum foil ? I have a thermometer with probe..

[newtothis]

Re: M421VT LED Screen Color Distortion

Ok NTT,,got some flux,,,what is your recommended procedure for doing the Ball Grind flow with the equipment I have ? Do I need to remove heat sink ? Do I need to protect other components with aluminum foil ? I have a thermometer with probe..

Ok right...

1) cover top area on the board leaving the BGA cut out, don't let the foil touch any Electrolytic Caps.. Aluminium is a really good conductor of heat and most people press it against the board which isn't clever... (Yes no heatsink)

2) You will want to hang as much if the board over the edge of a worktop weighting the one end down to keep it stable... You need to be able to see as much of the bottom of the board as possible.

3) Flux all around the BGA

4) With heat gun in hand warm the bottom of the board all over checking with your thermo probe right next to the BGA, You want to get the board to around 180c

5) From around 10cm away heat the BGA trying to gently get it to around 200c and hold it there for 60 seconds (This allows any moisture to escape slowly avoiding popcorning)

6) Keep transferring heat to bottom of board to maintain even temps... bottom heat is more important than top heat

7) from 5cm away from BGA heat gun it checking the temp every 30 seconds.... Solder needs to hit 217c to reflow. When you get close to that temp you are going to want to either A) tap on top of the BGA every 10 seconds or B) nudge it from the side... This has to be done ever so lightly.... You will see the chip bounce or move when done if the solder is molten.... As expected don't want to push it hard... The solder surface tension will hold it in place though.

8) When you see it has moved remove heat and leave it to cool for some time so you can handle it.

Good Luck

[dfang]

Re: M421VT LED Screen Color Distortion

Ok right...

1) cover top area on the board leaving the BGA cut out, don't let the foil touch any Electrolytic Caps.. Aluminium is a really good conductor of heat and most people press it against the board which isn't clever... (Yes no heatsink)

2) You will want to hang as much if the board over the edge of a worktop weighting the one end down to keep it stable... You need to be able to see as much of the bottom of the board as possible.

3) Flux all around the BGA

4) With heat gun in hand warm the bottom of the board all over checking with your thermo probe right next to the BGA, You want to get the board to around 180c

5) From around 10cm away heat the BGA trying to gently get it to around 200c and hold it there for 60 seconds (This allows any moisture to escape slowly avoiding popcorning)

6) Keep transferring heat to bottom of board to maintain even temps... bottom heat is more important than top heat

7) from 5cm away from BGA heat gun it checking the temp every 30 seconds.... Solder needs to hit 217c to reflow. When you get close to that temp you are going to want to either A) tap on top of the BGA every 10 seconds or B) nudge it from the side... This has to be done ever so lightly.... You will see the chip bounce or move when done if the solder is molten.... As expected don't want to push it hard... The solder surface tension will hold it in place though.

8) When you see it has moved remove heat and leave it to cool for some time so you can handle it.

Good Luck

Hello NTT,
I finally got around to attempting the BGA on the VIZIO main board...Unfortunately I failed. I followed your instructions (which are very good) but,,the problem came at the point of the last hi temp application (217c).

my assistant had the temp probe on the chip monitoring the temp and when the probe was removed it lifted the chip from the board and little balls went rolling,,lol..

So,,,I'm trying to find a TXACB5K05302 main board,,they are hard to find right now,,got a request in at SJ...

Thanks again for your help..
I did learn a lot..

[newtothis]

Re: M421VT LED Screen Color Distortion

Hello NTT,
I finally got around to attempting the BGA on the VIZIO main board...Unfortunately I failed. I followed your instructions (which are very good) but,,the problem came at the point of the last hi temp application (217c).

my assistant had the temp probe on the chip monitoring the temp and when the probe was removed it lifted the chip from the board and little balls went rolling,,lol..

So,,,I'm trying to find a TXACB5K05302 main board,,they are hard to find right now,,got a request in at SJ...

Thanks again for your help..
I did learn a lot..

Oh no!

Should of had the probe against the board next to the BGA and not on the BGA itself... Though you managed to get the reflow which is good You know how to do it now but next time (if ever) don't lift the chip LOL

Sorry it didn't work out for you but it was at least worth attempting first