DELL E176FPf 2 Secs To Black

[coppercitycomputer]

Got this DELL E176FPf from the scrap yard, turns on for a few secs then shuts off, led stays on. I can hear odd noise from the power supply board almost like a crunching sound not a whine.

I removed the board and don't see anything that looks bad? Where do I go next?

[SteveNielsen]

Re: DELL E176FPf 2 Secs To Black

Maybe arcing/sparking making the sound. Check the CCFL wires & connections for signs of burning.

[coppercitycomputer]

Re: DELL E176FPf 2 Secs To Black

Nope, everything looks good no arching that I can see. Can't see any burning,

[SteveNielsen]

Re: DELL E176FPf 2 Secs To Black

Next thing comes to mind is an inverter transformer shorting, arcing internally.

[coppercitycomputer]

Re: DELL E176FPf 2 Secs To Black

Ok, Thanks I will plug it up outside the case and see if I can see anything or pinpoint the noise.

[SteveNielsen]

Re: DELL E176FPf 2 Secs To Black

BTW I have one of these monitors I repaired a year or so ago (replaced caps in the inverter section), and I thought I had the schematic for it but apparently not. There are a few other threads here discussing this monitor if you haven't already looked at them.

[coppercitycomputer]

Re: DELL E176FPf 2 Secs To Black

The sound is a hiss and it only happens when T2 has to drive both CCFL tubes, If I unhook one of the CCFL tubes (it's leads wire connector) the hissing stops, I can't tell if it's coming from the panel or the board. T2 is the inverter in the lower right hand of the photo. Still 2 secs to black even if some of the CCFL are unplugged.

[budm]

Re: DELL E176FPf 2 Secs To Black

You will get 2-second to black if one of the lamp is bad, does not light up, or does not stay on after 3 seconds, it is part of the protection circuit.
You should remove the transformer and inspect it real close, also check the secondary side (high voltage side) winding resistance. The hissing sound can also come from the lamp due to bad solder joints, wire insulation break down, or crack lamp.
Bad lamps:
http://s807.photobucket.com/user/bud...?sort=3&page=1

Bad transformers:
http://s807.photobucket.com/user/bud...?sort=3&page=1

[coppercitycomputer]

Re: DELL E176FPf 2 Secs To Black

Thanks everyone for the help, I checked out the transformers they seemed good. So I tore apart the LCD panel and sure enough one of the CCFL tubes is very black and burnt. One tap with the screw driver and it just broke. not worth fixing at this point.

[budm]

Re: DELL E176FPf 2 Secs To Black

Thanks for the follow-up.