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Samsung LE37B551. White picture

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Davy:
Have Samsung LE37B551, you can just about see the picture and on-screen menu but they are far too bright.

The PWM on pin 3 to the inverter from the main board doesn't alter any, voltage or waveform when viewed on a oscilloscope no matter the brightness setting.

Checking on the bench it did fire up OK a second or two then gradually turn to 'excessive white', just like some CRT screen faults.... it only did this once.

Anyone know how to reset the CPU and if a manual is available thanks.

Dave

Turnip:
Hi Davy,

Wonder about the screen used, as some are a bit suspect with this problem, but not usually 37 inch so far.

Chris.

downunder:

Hi Davey,

That sounds like a faulty gamma chip on the T Con.....AS15G, H, or U. Remove the T Con cover and see if it's got one, a smallish 48 pin postage stamp. A very common fault on a host of brands. Not easy to replace unless you've got good soldering skills, otherwise a replacement T Con could be the go.

Bruce

Davy:
Hi Chris and Bruce, thanks for quick reply.

Dunno what brand the screen is it's on my mates bench, he's not a TV engineer, can only see a couple of components on the Tcon, the bottom assembly needs be removed to get at.

I'll have a look tomorrow when I pop round, must be loads of Tcon boards kicking about, might even have one myself, well and truly buried in this set.

I thought with no PWM activity voltage or waveform wise from the main board to pin 3 on the inverter/psu board (all in one) when the brightness is altered.

Chris, when you say screen are you meaning when a part of it goes dark? I've never come across this fault myself..... could be a clue here if I say the picture does look ghostly no doubt one of you guys are right.

Thanks again for your help, I appreciate it.

Dave
 

downunder:

Hi Davey,

I get your drift, T Con is under the pedestal mounting hardware.
Can see the CCFLs being turned on to such brightness levels as to cause an over-bright picture. The inverter protection senses average current used by the CCFLs and would activate protection.

My money's still on the gamma chip.            Bruce

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