Sony KDL-26L5000

[MisterD]

A friend asked me to see if I can fix this Sony 26" LCD TV. It has been sitting for awhile and when I first plugged it in it came on and had power on light, I left it on for about 10 secs, then unplugged it to move to another location, since then I have not been able to power it back on and the STBY Light in front is not lit. I have voltage readings as follows.

PS Board

P on 2.6 V
AC Det 2.7 V
ST BY 3.3 V
Unreg 15V is 16.3 V on both pins
Reg 12V is 11.9 V on both pins

Connector on PS Bd that connects to Inverter Bd

Reg 24V has 24.7 V on all 4 pins

3.3 V is present on both the IR Board and the On/Off Switch board.

Back Light will come on if I unplug small 3 wire connector (CN202) located at the top left of the Main Board, shown unplugged in Picture.this goes from the main board to the inverter board.

I have tried freeze spray and heat on the Main bd. processor and got no response at all.

Any help is appreciated. Thanks in Advance.

[CapLeaker]

Re: Sony KDL-26L5000

If you got standby voltage going to the main board, no reaction on the Power LED and no PSON signal coming form the main board to the PSU, while trying to turn on the tv, looks like a bad main board to me.

[MisterD]

Re: Sony KDL-26L5000

On left side of main board 3rd connector down from top is CN4201 and has 0v at black/top wire, 3.2v at middle/brown wire and 3.2v at bottom/red wire, when on/off switch is pressed the pin at the bottom red wire at this connector drops to 0v, then returns to 3.2v when on/off button is released. I'm not sure if this is normal.
I think the problem is on the main board, I'm going to remove it later and inspect the back side of it.

[newtothis]

Re: Sony KDL-26L5000

Ignore: missed something in previous post

[MisterD]

Re: Sony KDL-26L5000

I have 385 VDC across the main capacitor, removed and inspected main board, no signs of any burnt traces or bad solder connections as far as I can tell.
Could be the BGA connections are bad on the main processor, not sure.

[budm]

Re: Sony KDL-26L5000

I have 385 VDC across the main capacitor, removed and inspected main board, no signs of any burnt traces or bad solder connections as far as I can tell.
Could be the BGA connections are bad on the main processor, not sure.

Right now you are getting the PS-ON otherwise you will not have the boosted Voltage, the 24V, 12V, ect. PS-ON is stuck at this point, may be.
The connector that you removed there are pin names which I cannot read due to the picture is not focused, what are the names for those pins?

[MisterD]

Re: Sony KDL-26L5000

The connector that you removed there are pin names which I cannot read due to the picture is not focused, what are the names for those pins?[/QUOTE]

Those are reference numbers for components, R212, C201, R259, R217. Unfortunately there are no pin names at that connector only the reference CN202

[budm]

Re: Sony KDL-26L5000

OK, I found good pictures at SJ, and can see the connector now.
http://assets.shopjimmy.com/media/ca...2-21-top_1.jpg

So right now the problem is in the main board and I do not have any idea at this point which part/s are bad.
What happen if you disconnect the button board? The TV is on without pushing the power switch (the boosted voltage and other Voltages are present).

[MisterD]

Re: Sony KDL-26L5000

Bud, I disconnected the button board and there is no change, all the voltages are still present but no backlight, no picture, no sound and no standby or power light in front.
This tv did show a picture and powered on (without me pressing the on/off switch) as soon as I plugged it in the first time but would not power back on once I unplugged it then plugged back in, I think it had been sitting unused and put away for several months.

[CapLeaker]

Re: Sony KDL-26L5000

I think I see 6 voltage regulators. Measure those. All 3 tabs against GND, with numbered pins and whatever is printed on the regulators.

[MisterD]

Re: Sony KDL-26L5000

I just took a hair dryer and heated up the main processor real hot on the main board while the tv was plugged in, then unplugged the tv and when I plugged it back in it powered on with sound and picture.

I suspected this area all along, so the problem must be the BGA solder balls and some were not making a connection, using the hair dryer heat has expanded that area making them re-connect.

I know this is only a temporary fix but gives me the chance to check the screen and other boards so I know only a replacement main board is needed to fix it. Still up and running for 20 mins now. I haven't had much luck with reflowing BGA processors

[newtothis]

Re: Sony KDL-26L5000

Shame your not in UK, Just moving on to BGA rework and get my IR station and tools tomorrow to start practice.

I have extensively researched BGA reflows and profiling for some time now, Successfully done smaller package BGA with hot air alone.

It is possible without the proper tools but essentials are needed :

A multimeter with thermo capabilities and a thermocouple or a dedicated K-Type.
Good flux (I recommend Insat Super)
Something to preheat the board (Ideally from below... You want to get the board upto around 180c before any rework is carried out on the BGA package, ideally 3c per second then let it soak for 60 seconds)
A regulated heat gun (Obviously an SMD station is best) - You want to hit the BGA and get the temp upto 215-220c at around 2c per second

This is best chance of success.

You could of course if you were going to replace the board just heat the whole thing in the oven and got the board hot and hit it with a heat gun til the solder melts under the BGA (Nothing to really lose in trying) Again Insat would help a lot!

[MisterD]

Re: Sony KDL-26L5000

It's my understanding that the board should be flat and not vertical while doing a reflow to prevent the solder balls from shorting together due to gravity when they melt, I also understand that flux can keep them from shorting together

I worry about other small Components falling off the board(due to melting solder)when it's heated at that high of temperature.

Should the board be placed in aluminum foil while in a oven? How long and what oven temp?

Thanks.

[newtothis]

Re: Sony KDL-26L5000

The unorthodox way of doing it in the oven is by covering any exposed areas other than the BGA in foil (So wrap it and then cut only the BGA area out)

You just want to get the board hot so you don't have to heat gun the BGA for as long.... Baking the board allows moisture to escape to avoid popcorning and avoid having the BGA at critical temps for too long.

Yes it has to be flat... sit the board on 4 balls of foil to elevate it from a baking tray... once the board has got real hot (Flux will be bubbling) hit the BGA with a heat gun from about 8cm above it.... with your spare hand you want to nudge the BGA with a pencil or similar very very lightly until you see it move.... the BGA will rest back on its pads from surface tension of the solder and the flux will stop bridges.

This is by no means a proper way of doing it... but if the board will be scrapped anyway then this way has the best chance of success with proper rework tools

[MisterD]

Re: Sony KDL-26L5000

Thanks newtothis for all the great information, I had this TV powered on for 2 hours last night and 4 hours today with no problems, I wouldn't think the high heat from a high powered hair dryer would have actually melted the BGA solder.

Instead of trying a reflow, I placed a piece of surgical tubing (that I have for use in tab bond repairs) in between the heat shield and thermal pad at the top of the BGA processor, reinstalled heat shield and tightened screws down to apply pressure to the BGA Processor.

If it continues to work as long as I'm testing it I will give it back to my friend to try, if it quits again will order a new main board Sony 1-857-322-21 ( SO22MAD) SB106-1 48.71I01.011 if available and they are willing to spend the money.

Thanks to everyone that chimed in on this. here's a picture of it working.

[newtothis]

Re: Sony KDL-26L5000

If the BGA has poor solder joints it WILL fail again trust me.... Found it real funny how people used to bolt the heatsinks down on Xbox360's in hope of reconnecting the poor joints... All it will do is warp the board due to pressure and break even more