Laptop LCD inverter

[janjan22]

Hi

I have a Amilo L7300 laptop probably with a broken inverter. I can still see a faint image of the screen but without the backlight. I measured directly at the output of the step-up transformer. I should measure a low resistance value but I got an infinite reading.

Because this is the secondary side of the transformer, could it be faulty CCFL's? Could it be caused by a short circuit somewhere at the secondary side.

Thanks in advance.

Regards

Jan

[Pentode]

The resistance of the HV winding is going to be high... the off-load output should be in the region of around 1,800V (1.8KV) but the running voltage with the CCFLs lit is around 1,400V and it's going to be around 18Khz in frequency or more, it's not going to be DC.

One quick test is to hold the two ends about 1mm apart and see if you can draw an arc or better still use a high voltage test meter... the tubes can also become faulty.

Dave

[Pentode]

I forgot to mention... make sure it's not the lid switch.

Dave

[joester]

My experience with inverters that have failed tells me that they usually have a failure of the insulation on the wires within the transformer. This shorts the transformer, and blows a section of the windings resulting in an open reading. No chance of repairing them unless you have way too much time on your hands and care to dis-assemble the transformer, count windings, rewind with new wire, and re varnish it.

Replacement is the best answer, and unless the screen was red or pink on initial start up prior to the failure, I would bet the bulbs are OK.

You can sometimes get lucky and find inverters that work in a variety of laptops. Look for assembly numbers on the inverter itself, and Google those numbers.

Good luck!

Joe

[janjan22]

Thanks for your help, I think I will replace the inverter for a used one. I will notice you if the laptop is working again.

Regards


Jan