Well, that depends... TI used several keyboards, Some good, other not so much. It's pretty easy to pry up a keytop and see what's beneath. Some are separate switches, but the contacts are hidden inside. Others have a pair of fingers that make the contact when you press the key. Accessible, but for some reason harder to keep clean. I'd blame it on weak spring action on the long fingers plus more exposure to air. Another keyboard variation has a membrane inside similar to the buttons in your TV remote or the Timex TS1000 (well known for it's frail keyboard). These are crap and almost impossible to repair.
I'm not familiar with the Hi-Tek to guess which design route it takes. If it's not a membrane style, it may benefit from a contact cleaner. The QD brand from CRC works well and is sold at places like Ace Hardware. De-Oxit is another product some folks prefer, generally costs more and it comes in several flavors, so read up on that product first. Other people like plain ol' WD40, which is actually a pretty good answer, and who doesn't already have some?
Not to muddy the waters. Basically if you can see or guess where the contacts are, a bit of spray in there and work the switch (safest with power off, of course), wait awhile to let the volatiles have time to evaporate. Power up and test.
QD happens to evaporate pretty quickly and does not leave much residue. I haven't seen it harm plastics, but it might leave a liitle film evidence that can be wiped off if it bothers you.
If you have a radio with a scratchy-sounding control or switch, this is the answer for that trouble as well. That's kinda why I went in to such detail. All that aside, I've been spraying and tweaking the fingers of the Function and right Shift keys on my beige TI to not much avail. I'm about to swap it out for a Black & Silver to see how well it has aged. So, YMMV. (I'm suspecting a bad solder joint in the beige unit's keyboard at this point).
I don't personally know how the Hi-Tek kbd is made, so this is all kind of a shot in the dark. Pop a keycap up and have a look what's beneath.
Here's one recent thread, there must be several others to read up: http://atariage.com/...-alps-keyboard/
Edited by Ed in SoDak, Sun Mar 11, 2018 2:05 AM.