My own #805 needed a lot of keyboard work!
First off, it was time to bend the pad arms back into the proper angles, for which Martin provided a template. In the first picture I'm putting a pad arm back on after having brought it back to the correct angles. Most of this type of work is a guessing game, though, when it comes to fine adjustments, but in general you get the major bend correct, feel out the minor bend at the pressure pad itself, then put the pressure pad back in with about 1/4-1/3 of the head exposed. And you hope that's it. :-)
Now, in the second picture I'm demonstrating the use of a special tool provided by the keyboard manufacturer. Under the keys you can see some green felt and some pins. These pins ride in a hole under the key. The hole in the key sometimes needs to be opened a little so it can ride on the pin easily. If you don't make sure of this, you will need to crank down the nylock nut at the back of the key to make sure the key returns OK, making the 'tron harder to play. So you take this neat crimping tool, put it in the hole, and squeeze. If needed, you turn it around and do the other side of the hole. Done---all of 805's keys now spring back like new, and the nylocks have been loosened up a bit.
After that it was adjusting the pads and pinch rollers...35 times! The Streetly method is to adjust the pressure pad first. You get the pinch roller down to where it's pulling the tape through, and you hold down a key and crank down the pressure pad until it sounds OK. Then you give it 1 turn. You then back off the pinch roller to where the tape stops, crank it back down until the tape goes through OK, then give it 2 more turns. Done.
I like a light touch to the keyboard, so I didn't tighten down the pad 1 full turn after full sound and the pinch roller two full turns after full tape movement. I think this didn't sit well with Martin, who doesn't like to see anyone adjusting keys when they swap tape frames. I figure I'll need to adjust things here and there, but eventually things will settle in...Not a biggie. I keep a toolbox near #805 anyway. :-)
Note: When you crank down the pressure pad, muffled to full sound should happen within about 1/4-1/2 turn. If this does not happen, then check the angles of the pressure pad and the alignment to the head. If you hear a muffled sound and it takes a few cranks on the screw to get full sound, something's out of whack there, so examine the pressure pad arm and felt.
Fritz gave 805 a whirl after I finished up the keyboard adjustment. Finally---805 got to be played by a real musician! Wow! :-) I had Viola/M300A strings/Mark II Brass in there that day.