Having a problem with the screen going dark on my G4 15" powerbook. It doesn't go completely dark - you can barely see windows. It is darker than the normal brightness drop screen saver.

No amount of typing or moving mouse restores the brightness. Closing and opening the case sometimes help. A restart so far has always worked.

Any ideas?

Either your backlight is dying or your a cable is getting pinched in your casing. We don't repair this problem.

-Bradley
Powerbookmedic.com

Is there anyway to test for if its the cable

Unfortunately there is no test you can do. I'd just take apart the unit and see if there is stress on any of the cables and make sure the inverter cable is plugged into the inverter board correctly.

-Bradley
Powerbookmedic.com

The LCD screen on my 500 MGHz Powerbook is also going to a very dark gray, but with a twist. If I put the Ti to sleep or turn it off for a few days, when turning it back on, the screen is OK. Then over time (and that time is getting shorter) the screen starts to quickly flash to all white for a while, then I get fuzzy vertical 1 inch lines for a while, and finally goes to all dark gray (almost black). Then periodically wihtout any obvious reason, the screen comes back to life, shortly, and then the process starts over again. However, most of the time it is just dark gray. The external monitor connnected to the Ti is fine.

It doesn't seem to matter whether I jiggle or move the screen or if the Ti is running from battery or power. Any ideas what the problem is and how do I get it fixed?

Thanks,

lmbass

Hook the laptop up to an external display. If the display doesn't have linese or problems, then the problem is your logic board. Otherwise it is the display.

-Bradley
Powerbookmedic.com

Ok, an external monitor works great. So if it's my logic board, what next? Is there a fix, if so how much, or is this Mac toast?

A logic board repair on a 500mhz is $499.95 + $65 repair labor. Email us at support@powerbookmedic.com for more info.

-Bradley
Powerbookmedic.com

Hi,

I had the replaced the inverter board and associated flat cable with units from Powerbookmedic yesterday to address the screen flickering problem discussed. However, the replacement unit (and associated cable) did not resolve the problem.

It has been mentioned in these forums that the problem may be pinched cables. I had not noticed any pinched cables in my unit and took care not to cause any of this on reassembly.

While attempting to repair the unit I did, however, note that the inverter board is affixed with a screw which passes through an aluminum block/armature. This armature applies considerable pressure to the inverter board when the screen is moved. Is this engineering flaw potentially damaging the inverter board? If so, is there a suggested solution to this?

As my Ti screen shorts out when either the screen is moved or the case is twisted slightly and it has been suggested, by Powerbook Medic in the forums covering this issue, that the problem could be caused by - in decending order;
a) inverter board
b) pinched cable
c) logic board

As my particular problem is only present when the unit is at operating temperature this suggests, perhaps, that expanding metal is causing the short to occur in either the inverter board, cable (which one) or logic board.

(As it has been suggested by PowerbookMedic in these forums that the logic board could be the problem) what could be damaged on the logic board that causes this short - and not the total failure of the board? I replaced the large flat cable connecting inverter board to the logic board with no resolution to the problem.

If the problem is related to the small cables carrying current to the screen, what solutions are available or suggested?

I believe we answered your question in an email. You're looking at either the logic board or a crimped inverter cable most likely.

-Bradley
Powerbookmedic.com

ok, so why not share the "email" with us...i am haing the same exact problem mentioned in the post quoted here...anyone? seems llike this might not be the place.. i have a 15" tibook 500MHz 512MB RAM

I don't remember the specific email as we get over 500 a day. I believe the case in this issue was the logic board however.

-Bradley
POWERBOOKMEDIC.COM

Hi, re: your screen dimming problem.

I have replaced the logic board on my 15" Ti and this has solved the problem. It would appear that there was a crack in the board that shorted the trace running to the inverter board circuit - making it appear to be the inverter board at first. However, after replacing all the parts related to the inverter we refocused on the habit of the screen to go dark when the screen or frame was moved/distorted and even typing sometimes caused the screen to dim out.

Unfortunately, it is hard to eliminate the faulty part(s) except by replacing them. If you have replaced the inverter & related components then the logic board may be your next target. I was able to find a good used logic board from a local repair place - they often have lots of dead units they have stripped of their screens.

Good luck.