SHARP LC-60LE640X display flashing white noise patches and totally dropping out randomly

[dmcabs]

Hey guys,

I have a SHARP LC-60LE640X TV that has suddenly developed an intermittent fault of flashing white noise patches (appears like an Analog tuner off signal) and then totally dropping out.
This model I believe is also known as LC-60LE600U or LC-60LE640U in other regions.

FYI, a long time ago I was a component level repair tech for all consumer electronics and IT equipment.
I'm a bit rusty but still have ability to dig right down.

I measured all power supply lines and checked them for AC ripple voltage. Noting any lines that exceeded about 5%.
I found a few so decided to replace all electrolytic caps in the power supply and the Tcon board given the age of the tv.
In the service menu the power on hours was almost 25,000hrs, so fair to replace all electrolytic caps.

On the Tcon board there are 3 switching regulators that are filtered by SMD Ceramic caps. I have ordered these caps but have not replaced them yet.
This would be the last section of total re-capping the TV (apart from anything on the CPU board which I have ignored so far).

After the re-capping, the time between the intermittent display issues has lengthened significantly but not totally resolved.

Has anyone had any experience with this model and issue?
The AC ripple on the 3 switching regulators on the Tcon board are under 1%, but does not rule out ceramic cap faults.

Any ideas guys?

Thanks so much.

[lotas]

In this chassis, the BGA processor usually fails, requiring reballing of the BGA processor.
And according to backlight errors, errors are written to the eeprom (if the number of “Lamp error” errors exceeds 5), the TV is blocked.

[dmcabs]

Hey Lotas, thanks for the quick reply.

Are you referring to the BGA processor on the CPU board or the Tcon board?

Are you saying the solder joints under the BGA fail, or the BGA device itself fails and requires replacement?

Regarding the "lamp error" counter exceeding 5 and the "TV is blocked", what do you mean it is blocked? The display still works, just intermittently drops out.

[lotas]

Yes, the CPU on the motherboard is destroying the bga soldering. If the backlight is not working properly, if you turn on the TV 5 times, then the 6th time it will not turn on, you need to change the backlight and reset the error codes.
If it turns off, check the panel, disconnect the cables going from the T-con to the panel one by one and check if it turns off.

[dmcabs]

Thank you for the information. Since the TV is quite old now, instead of reballing the BGA processor, I want to try just reflowing it first. Is this worth doing in your experience?
I found that the thermal pad on the back of the BGA processor has been seeping silicone everywhere, on the back of the pcb and also through the vias under the processor and then under the processor and on the top of the pcb. In this situation if any connections to the processor have become slightly disconnected, the silicone oil will make conductivity worse. I rinsed under the processor with 100% isopropyl alcohol already in preparation for reflowing it.

[Diah]

what you did saw had nothings to do with BGA... since the set old the martial of main boards and soldering are different as now fays.. they can hold ext ern heat for example use your kuchen oven to 260 " heat it and put the board for 10 minute.. turmoil and don't move it till it cool down..... ye this is nor my way to write but its better than to scrap the TV before to try

[dmcabs]

Thanks for the information. I agree the quality of manufacturing has reduced now days. Older equipment was made better.
About the BGA, you said has nothing to do with it. What do you mean? What do you think the fault is?
Should i still consider reflowing the BGA?

[Diah]

I found that the thermal pad on the back of the BGA processor has been seeping silicone everywhere, t.

regards to this.... however u need to give try for BGA

[dmcabs]

Thanks, I will reflow the BGA with proper flux for BGA and use SMD hot air rework station.
I powered on the TV today and now it will not turn on. It has two short red led flashes then off. Service manual says CPU communication error, so I would say you are right, it's the BGA.

[nomoresonys]

check some of the diy reflows on youtube, you need to get the chip to the right temp, too hot and can kill the chip, not hot enough then nothing happens. Best to bring the temp up gradually, some type of temp gauge is handy for that. Goal is to bring up temp gradually to melt solder, go another 30 seconds or so with same heat keeping the nozzle moving around the chip, back nozzle off gradually.

[dmcabs]

Thanks for the tips! I have done lots of smd soldering by hand and using a hot air rework station, all for.small parts, but I have never reflowed a BGA.
I have a few type K thermocouples. I can use them to monitor temperature.
Should I also apply heat to the back side of the board?
I only have a metal hotplate, i guess this is better than nothing.