Macbook A1181 Screen Problem

Hi there my 4 year old MacBook 13.3 ( Leopard ) has the aparently common screen dimming fault. I have since brought a new MacBook Pro but would still like to get the other fixed.

As it was a few months ago the fault occured I cannot remeber what I was using my Macbook for at the time but I do remeber the screen going black (very dimmed) and then not changing at all. I pressed the brightness buttons repeatedly but still no screen change, I tried restarting it but still no luck. After research I came to the conclusion if must be something to do with the backlight inverter. I ordered a new one off eBay and when it came I dismantled the MacBook (completley) to get to the pesky inverter. Whilst I had the broken inverter out I tested the connection of the cable using a multimeter and got a postive reading meaning it was not a faulty cable. After replacing the inverter and carefully reassembling the Macbook (making sure all cable were not pinched and connections were correctly connected) I fiered it up expecting the fault to be fixed...however I was greeted with the same very dimmed screen. I have done further reseach and tried most claimed soltuions such as

- starting it in safe mode and then restarting it

- changing settings in system prefrences

- resetting system management controller

- resetting the PRAM

The status the macbook is at now is...the screen is still very dark, I can see it using a flashlight or if I connect it to a external display. I had some positivity as the screen does appear to work if I do the classic 'speed-hit' the brightness button on its lowest setting to the first bar (dim to bright repeatedly) but does not last and soon returns to a very dimmed screen. Can anyone help me!? Is it hardware or software? Could it possibly be the logicboard? As said when the screen does work (can range from 5 seconds-a couple minutes) it is not affected by movement or screen tilting but can be affected by rapid change of brightness using F1 and F2.

HELP!