Philips 46pfl9706m bad video, need reflow?

[Davi.p]

Hi, i'll try to explain better than i can, sorry no pictures, i'm not organized..
This smart tv i have bought by second hand already broken, previous owner said he carried it to 3 Philips services and all said "bad panel".
He said first it showed "mixed colors and it freezes video" then after black screen no backlight...
I have found a bad linear voltage reg. for 2,5v on the FRC board, without 2,5v all the chain of other voltages doesn't switch on, also the switch that feeds power to tcon, this board controls also backlight so this is why no BL (?), i have changed it with a similar chip, i don't remeber well why, self destruct? .. My operation?.. but the reg blown again, i have ordered another one (equal) but since the long wait from China instead of mounting the new one i have supplied 2,5v from ext. PSU, in this way tv showed a Philips LOGO perfectly at power up, some seconds then some garbage pixels then a screen full of wide bars and some lines from top to bottom and steady. Letting tv warm a bit with this screen then switching off and on Philips logo donn't be showed again, letting cool it and newly LOGO on powerup..
First i've thought of bad firmware but there was some colors fade transition that don't remember bad data sent to screen, then i've thought of bad CPU and hopely bad bga soldering, so i've started reflow.. my questions:
1. what do you think about defect?
2. Reflow came bad, i have warmed some stripes of gel flux to flow under the chip, then i have masked around the chip with thick alluminium foil, then i have warmed a bit the chip, then under the board in the chip zone, then i have warmed the chip for some minutes always with my heat gun at 300C about, but with a tweezers in the corner the chip never moved. The result is that i have no more video. Which technique i can use to melt all the chip's tin?

THANKS.

[diif]

Re: Philips 46pfl9706m bad video, need reflow?

Is your heat gun a hot air station ? If so 300c won't be hot enough. I have mine at 380c for removing SMD components.
I wouldn't use mine for reflowing on its own. You need to heat the whole of the board to about 100 before using the hot air from above. There are those that just use the big paint stripping heat guns but they could very easily burn components and the board if not careful.

[Davi.p]

Re: Philips 46pfl9706m bad video, need reflow?

Is an HEAT GUN, on the manual sheet it says only 2 temp/air speed: 300/600 C.

"There are those that just use the big paint stripping heat guns but they could very easily burn components and the board if not careful."

But if 300C is not enough how can damage boards? Maybe at 600C? And why no picture now? I have cooked CPU? Surely no smd
surrounding chips flight away..

I use a self made nozzle that reduces the air exit hole to a circle of 1,5cm diameter approx. and i make circular movements aorund the chip, does this matters?

Bye and much thanks..

[diif]

Re: Philips 46pfl9706m bad video, need reflow?

I've only ever reflowed/reworked with a commercial rework station.
Did you measure the temperature on the board ?
You've either killed the IC or unsoldered more balls.
Did you apply flux before adding heat ?

[Davi.p]

Re: Philips 46pfl9706m bad video, need reflow?

"Did you measure the temperature on the board ?" Do not have termocouple..
"Did you apply flux before adding heat ?" Yes i've said.. I don't know if it flowes to center pins..
I think it has on the center pins many balls connected to ground plane that is too much wide to let the chip balls melt, but i have reflowed with success an LG 42" led tv, now sold months ago, no problems reported. The chip was a bit smaller and completely flat, this instead have a shiny mirror looking center square core..

[dskall]

Re: Philips 46pfl9706m bad video, need reflow?

I would invest in some temp monitoring if you are trying to reflow. Also you need to heat from bottom as well as top.

[Davi.p]

Re: Philips 46pfl9706m bad video, need reflow?

I've tried to warm all board but the temp remained low also after over a minute of circular warming, i was able to touch it a second without problems, i have warmed also the chip but never moved, just to make sure, i've tested it and now i have again Philips logo, i cant test sound because speakers are on the base (stand) and is not comfortable.. i'm wondering if using high temp 600C setting can warm the thing enough, or i need a new idea, (no oven, i don't want dioxine in my dishes).. thanks bye.

[dskall]

Re: Philips 46pfl9706m bad video, need reflow?

Have you checked for short if you are blowing regulator?

[Davi.p]

Re: Philips 46pfl9706m bad video, need reflow?

Is the end for the board, i've tried to warm up the bottom at 300C, then the top at 300 then 600C, then warmed the CPU at 600C not so near, 3 cm, no movement of the chip, at a certain point i've noticed 3 little tin balls arround the top inner square portion of the chip, that is at higher level than the green rest of the chip, with glue around, i think the tin exploded out from an invisible hole in the glue, it happened to me earlier on a laptop mainboard, tested the board the tv is 100% dead , no sign of life. Need a new mainboard. BYE.