PowerBook 1400cs fluctuating backlight

[68kAlex]

I've recently inherited a 1400cs with a peculiar backlight problem and I was wondering if anyone could shed any light on it.

When starting up, contrast usually goes really low and has to be cranked back up again manually. I gather this is not unusual on PowerBooks. Nine times out of ten the computer will then run fine with zero screen issues.

However, very occasionally I have noticed the backlight fluctuating completely randomly - at first just faint flickers, then gradually more and more extreme, on one occasion almost going black for about a second before returning to normal. Restarting solves the issue (temporarily).

On one occasion I also started the machine and was unable to get any brightness out of the backlight at all. The screen simply stayed black.

Are the capacitors in the screen on the way out, or is it likely to be some other issue? Cheers folks!

 

[uniserver]

I think its related to the caps on the inverter board.

That is what it sounds like to me.

One thing, I noticed when your PRAM battery goes dead, once you power the machine down. and then power it back up

it looses its brightness setting, defaults to low.

 

[68kAlex]

Thanks for the feedback. The PRAM battery on the 1400 is long dead so that would explain the contrast behaviour at startup.

I was hoping it wouldn't be the inverter caps as they seem to be a swine to replace!