Yamaha KX88 Self Test and After Touch Adjustment (see more for important NOTICE)

WARNING: Do not press on the keys too hard to get After Touch to work. This could break the keys. If your After Touch is not responsive, it would be best to replace the After Touch sensor strip. That is for advanced users as ALL of the keys would have to be removed. I have on video on KX88 key removal. There are many techniques to remove and install the keys, it is a delicate process. Yamaha does offer replacement After Touch sensor strips and keys, but I don't have a source for ordering them.
NOTICE: The Self Test will reset the KX88 to its factory state after the Self Test is exited. There is supposed to be a way to leave the KX88 in the same state as it was before you started the Self Test, but to be honest, I tried to do it once and it's very easy to forget what button to push. So if you get to the battery Test and press TS1, Self Test will end and the KX88 will lose all its settings. I need to revist that feature, but in the mean time, if you perform a Self Test, just expect your settings to be set back to factory default afterwards.
This video shows how to perform a Self Test on a 1980's Yamaha KX88 Master MIDI Keyboard. It also contains some information on adjusting the After Touch sensor.
During this video, I open the KX88 to gain access to the After Touch adjustments. See my other videos in the Yamaha Synthesizers playlist on how to open the KX88 main panel.
The number "22" displayed when entering Self Test mode may differ on your KX88. It is believed that this is a firmware version number. If your version number is not 22 as it is in mine, your self test may vary slightly compared to what I show in my video.