My beloved Enhanced IIe (PAL version) has suddenly developed a fault. As soon as it's powered on, it goes into the diagnostic mode and loops around forever. If I hit ctrl-reset there, the diagnostic starts up again. It's as if the Open and Close Apple keys are pressed permanently. However time to time, I can hit the ctrl-reset to go into BASIC prompt. I wrote a little program to see the Button 0-2 values and most of the time, it's = 160, though time to time, it momentarily dips below 127. I presume that's when I can go to BASIC prompt, if I hit ctrl-reset at that moment while in diagnostic mode. I have unplugged everything from the machine to no avail.
I don't believe the keyboard has gone bad. I can type BASIC program after all. From the IIe schematic, I can see that buttons (and Open / Close Apple keys) are wired to LS251 multiplexer. Do you think it's faulty? Just my luck, it's soldered without a IC socket.
Also (as I usually don't do this, I can't remember), does the holding down Open and Close Apple keys while powering up make Apple IIe to go into diagnostic mode? That would explain why IIe goes straight to the diagnostic mode when I power it up.
Thank you for your help