[elequix]

Hello!

I have an ibook G4 1.2ghz that came to me with a keyboard issue wherein each time the '5', 'T', 'G' or 'B' keys (note that these form a diagonal line on the keypad) are pressed individually, the other characters in that "line" are also inserted into whatever text field is selected. Typically, a 'B' keystroke will result in "tgb', while the 'G' stroke will give 'ttg' and sometimes '5tg'. The '5' stroke intermittently raises the volume via 'F5' (also on that diagonal line of bad keys).

I have completely disassembled and thoroughly cleaned the keyboard, checked the ribbon and connection point - all seem solid. I dropped in a known-working ibook keyboard from another G4 and the same problem occured. OS versions have included 9.2.2, 10.4.4 and 10.5.4, all of which have had the same keystroke issue.

The problem briefly (1hr) corrected itself after the system was being highly stressed and became very hot (fan unit broken as well). After the processor reached ~125degF (accoording to iStat), the keyboard functioned fine until temperatures began to cool. I have duplicated this anomoly once more via loading the processor again, but subsequent attempts have seen the keyboard issue still present.

Has anyone encountered an issue like this before? Any ideas or suggestions on repair routes? Does anyone know how the keyboard input is handled on this series?

Thanks!

[ibook_steve]

The PMU manages keyboard input. Try resetting PRAM and the PMU. If these don't work, the problem is on the logic board (a short or some other problem with the PMU). I can't explain why overheating would fix the problem temporarily.

Steve