Ray, just to confirm : you're saying that if you remove the flat cable from the motherboard, your T1100 does not say "NO KEYBOARD" ?
Correct. "NO KEYBOARD" does not appear.
And I confirmed it again, today.
The fact that is a multi layered board does not help, as there are traces I simply can't follow.
What I do is put my multimeter into continuity mode (i.e. beep at low ohms), put one probe on the reference pin, then run the second probe over the pins of all components (i.e. not only the chips), listening out for a beep from the multimeter. In continuity mode, my multimeter beeps at anything under 100 ohms, and so when I hear the beep, I check to see that the ohms shown is zero or up to a few ohms.
I don't understand what could be wrong
If a similar problem existed on my T1100's system board, then I would be 'in the same boat'. Because without the faulty bit being visually faulty, I would need the T1100's circuit diagrams, source code, and a good understanding of how it all 'works in concert'.
Many hours would be required to create a circuit diagram of the T1100's system board. And some disassembly of the system board's BIOS to see what triggers the POST to display "NO KEYBOARD".
On mine, either that controller is dead and my T1100 is worthless, or something prevents it from starting (hopefully that's it)
Wanting to see the KEYBOARD ERROR message for myself, I tried some experiments.
With the keyboard connected, I held down the H key whilst powering up the T1100. Odd was that the RAM test only went as far as 80 KB (well, on-screen anyway). But no KEYBOARD ERROR message. Multiple H keys appeared to have been registered because the 'Place system disk in drive. Press any key when ready.' sequence ran for quite a few iterations.
Okay, so I will 'disable' the 80C49. I tied the 80C49's /RESET pin (22) to ground. No KEYBOARD ERROR message during POST !!!
Confirmed that the 80C49's VSS pin is connected to the ground running about the system board. And VCC is tied to +5V. So it wasn't a case of incorrect ground being used.
- Instead, short circuited the 80C49's two XTAL pins. No KEYBOARD ERROR message during POST.
- Instead, tied the 80C49's EA pin to ground. No KEYBOARD ERROR message during POST.
- Instead, tied the 80C49's EA pin to +5V. No KEYBOARD ERROR message during POST.
The above suggests that the keyboard test in the POST is not communicating with the 80C49 !!!
I went back to tying the 80C49's /RESET pin to ground. I then powered on the T1100. Again, no KEYBOARD ERROR message. And pressing a key on the keyboard works (specifically, at the 'Place system disk in drive. Press any key when ready.' message, pressing a key triggers another attempted read of the diskette drive).
So, with Toshiba indicating that the 80C49 is a keyboard controller in the T1100, how is it that disabling the 80C49 still allows the keyboard to work ?
Are Toshiba lying to us by indicating that the 80C49 is a keyboard controller in the T1100 ?