CCFL back light problem

I have a Dell Inspiron 1545. When I got it, the screen was smashed. I found a replacement screen, when I turned it on, I saw the LCD get power but then went black. With a flashlight, I could see Windows had loaded. I ordered a new inverter and it did the same thing. Less than a second of backlight then gone. So I ordered a new video data cable and another inverter. It did the same thing again. I pulled the screen and connected the backlight to an HP laptop and the backlight works fine.What is going on here? Why would it keep blowing inverters? Oh, the replacements were genuine Dell, not aftermarket.

 

That's the screen you unplug the inverter first and the video cable connects near the top of the screen? I've only changed one CCFL(Cold Cathode Fluorescent Lamp) screen without a problem. Are you sure there isn't something more going on than just the inverter? Maybe something deeper electronically.

 

I believe that's what I'm asking in my post.

 

Look for a tiny SMD fuse on the motherboard, near the 40 pin video connector. If this is the problem, you can replace it without worry re deeper problems, because the cause was the breaking of the screen.

If you google dell inspiron 1545 backlight fuse f1 = 3a 32v you should pull up sites with photos.

If that's not it, I have no other suggestions.

 

Thanks. I'll look into that now.

 

It sounds like something else was smashed along with the screen, perhaps causing a short and high current situation.

As far as a fuse, if it were blown, it should not allow the new parts to fail. That's why fuses blow, to open the circuit so no further damage can occur. So I am suspecting crimped or cut wires or some other physical damage.

Also, I know several techs who always replace both the inverter and CCFL at the same time - even if one is still good.

 

Bill, you're right there, which is making me rethink whether I actually saw the backlight or was it just a change in the display when it got power. I'm going to locate the fuse and test/short it to see what happens. Be back later.

 

I sure do NOT recommend shorting (bypassing) the fuse - especially if it is blown. While fuses can fail and blow prematurely, it is not wise to assume the fuse was faulty and instead, you should assume there is (or at least was) too much current running through that circuit, causing the fusible link in the fuse to melt. Bypassing (shorting) the fuse with a wire or some other conductor could result in too much current through the devices the fuse is designed to protect.

You can certainly test the fuse with a multi-meter to see if good. And you can replace the fuse in the circuit to see if it blows too (using the same or lessor fuse). Hopefully, if blown, it was done during the smashing and once the smashing force (physical pressures) was removed, so was the short that caused the fuse to blow.

 

The fuse is blown. Looking into replacing it now.

 

Also as a precaution check to make sure the video cable is not crimped.

 

@ lj50,
Brand new video cable routed correctly. Thanks

 

You're welcome.