Ok, I've run across what might be the cause of the keyboard issue in my original post. Today I was playing around with the system after installing the disk drive connector cable that Ben Yates sent to me. I was using the NIB TI 99/4A that I bought last month and it was doing the same keyboard thing that I posted about at first. I unplugged it and tried another unit that had been working - same thing. I Turned off the PEB and unplugged the flex cable and speech synthesizer, still the same thing. I unplugged the TI cassette data recorder, also NIB, and .....PROBLEM SOLVED!!
I plugged everything back up except the cassette drive and everything works with all of my TI 99/4A units (I have four) except the very first one I bought - getting some double hits with some keys on it, might just be corrosion.
It has been about 30 years since I fooled around with a TI 99/4A. Is there a problem with my data recorder, or am I supposed to have a disk or module plugged in when it is hooked up? Funny that simply having it plugged in screws up the keyboard.