Brightness Control not working : Powerbook Duo 280C

[nvdeynde]

Hi,

The brightness control bottons are no longer working anymore on my powerbook Duo 280C.
I opened up the LCD housing as I though it was probably the brightness actuator but it tests good.

I had a spare logic board from a duo 280 so took a shot and swapped it to no avail, but we can exclude the logic board now.

I only see 2 possible options left: the inverter board or the LCD cable.
I'm toast anyway as these parts never come for sale on Ebay

Anyone else with this problem ?

[techknight]

it could be either a failed inverter, or a bad CCFL tube.

[techknight]

best thing to do is grab a DMM, and check the picofuse in the inverter to make sure its still good. if not, cbeck the transformer driver transistors for shorts and replace them along with the picofuse.

if picofuse is good, most likely the PWM IC failed.

[nvdeynde]

The CCFL is working, it's just that the brightness can't be adjusted anymore with the buttons on the LCD.
So backlight is on but probably on the lowest setting so the screen is hardly readable.

My Main battery and Pram were drained and appartently the brightness setting is stored in the Pram as the screen was much brighter the last time I used the laptop.

[techknight]

yes its stored in the pram. Cant you adjust the brightness with the screen control panel?

[nvdeynde]

There's no Screen control panel op my Duo 280c with Mac OS 7.5.5
I guess the Brightness can only be adjusted with the pushbuttons on the LCD.

[nvdeynde]

The invertor board appears to be faulty. I have tested all traces in the LCD cable between the invertor board and the logic board and they are OK.
I don't see how the invertor board can be repaired. It's not the socket to the brightness actuator, the invertor also works so it must be the controller on the PCB.

It's pitty as chances are next to zero of finding an invertor board for sale on Ebay. It even isn't the same as in the Duo 270c

If anyone has a spare one for sale, feel free to PM me.

[techknight]

I got a powerbook C series, i forget if its the 270 or 280 with a shattered screen.

if its a 280, Ill see if i cant dig it up, depending on where you live you might be interested in the inverter.

[nvdeynde]

I'm definately interested if it's the inverter of a Duo 280C. The one from the Duo 270C is different.
I'm located in Belgium ( Europe ) but since it's just a small PCB, shipment will probably be cheap.

[Bunsen]

Have you checked the connections to the buttons themselves, and whether the buttons work?

[nvdeynde]

Correction here: the inverter of the Duo 270C and 280C are identical.
I mislabeled a spare part: I appears to be from the B&W Duo 280. Sorry

[nvdeynde]

Have you checked the connections to the buttons themselves, and whether the buttons work?

Yes the buttons work. It's the inverter PCB as I have just taken my Duo 270C apart and swapped the inverter PCB: now the screen's Brightness can be adjusted again with the buttons.

So the cause has been found, now finding a replacement inverter board will be another issue...

[techknight]

this weekend when I get time, ill grab out the big box of old PB junk and pull it out.