Sharp IT-23M1U TV LCD, flashing distort

[tieny]

I just got a Sharp IT-23M1U LCD TV monitor with a problem. I would click the main power button and the power LED lights up green right away but it doesn't come on right away. After around 45 seconds the screen would turn on (screen is still black but lights up a bit) 15 seconds after it turns on, the distortion comes on for a second and would flash on and off every 4 seconds.

I'm not sure if this may or may not be a circuit problem. Would this be a problem on the video board? Whats weird is that it still displays (MONO) on top of the screen clearly. I'm still trying to figure out how to remove the back panel to check out the circuit boards but still having a hard time.

[Scenic]

Re: Sharp IT-23M1U TV LCD, flashing distort

Elektrotanya has the service manual. Disassembly instructions start on page 19.



Can't really help much at the moment, but I'd suspect a mainboard problem.

I've seen a very similar fault on a LG LCD TV before.. couldn't really find any info on the net about this sort of problem, so I ended up not buying the TV despite it being dirt cheap. It also had weird multicolored pixel-salad on the screen with the OSD showing up normally (no distortion etc.). I'm VERY curious to see what causes this.

[tieny]

Re: Sharp IT-23M1U TV LCD, flashing distort

Thank you!! I've been looking for the service manual and couldn't seem to find one. It was a pain taking it apart because of all the screws, but I made it to the mainboard.

I provided two photos of the same mainboard (the same board I just zoomed in half and half to get a better quality)

I found an oddly placed resistor in the first photo, I just found it weird, don't know if its relevant.

All the caps look normal and seem fine to me. I've checked all the fuses and I think I found a blown one (as shown in the second photo), couldn't get a read off the multimeter and no continuity. Lucky me I happen to have extra fuses of the same type! =)

Should I check anything first before replacing the fuse and where should I start (still new to circuits) I don't wanna replace it only to have it blown again.

[tom66]

Re: Sharp IT-23M1U TV LCD, flashing distort

That blue resistor with a bit of orange tack? That's a bodge job - but it's fairly common in consumer electronics. Boards are expensive, one component might be faulty (misplaced for example) so they bodge them on. Or, they might design a board but discover a problem later when they are released and they don't have the time to re-spin the board.

I think the fuse is the problem as it powers some video decode stuff. Worth a shot.

[tieny]

Re: Sharp IT-23M1U TV LCD, flashing distort

A bodge job? Does it usually come directly out of the manufacturer? Well I replaced the fuse and that did it! =) Its working perfect now.

But just curious, what are the causes of a blown fuse? Usually when a fuse gets blown from excess current wouldn't it get blowned again? Or could it be due to aging and eventually got weaker and wore off.

[tom66]

Re: Sharp IT-23M1U TV LCD, flashing distort

A bodge job? Does it usually come directly out of the manufacturer? Well I replaced the fuse and that did it! =) Its working perfect now.

Yes, the manufacturer pays people to fix the boards that don't work. Far cheaper than throwing away a £50 board.

Glad you fixed it.

But just curious, what are the causes of a blown fuse? Usually when a fuse gets blown from excess current wouldn't it get blowned again? Or could it be due to aging and eventually got weaker and wore off.

Essentially, it is thermal wear. It is common on T-con boards too for the fuse to blow, with no fault on the board itself.