Emu Command Station (MP-7) Buttons

Synth Repair
1

Hi all, I copped an MP-7 for $150 - woohoo! - ofc it needs some work :sweat_smile:

I’m wondering if there is a fundamental flaw with this physical keyboard design. My first clue was that 50% of the buttons on this instrument are unreliable or dead. Are other Command Station keyboards experiencing a high rate of failure? Am I missing something?

When I opened up the unit to replace the switches, I observed the keycaps do not sink straight down. They have a lot of play, and I think that’s wearing out the switches. It’s also not nice to press these buttons, bc it’s a combination of mushy and clicky and feels like breaking or wearing something out.

The keyboard design is similar to, say, the ASR-X. On that panel/PCB, the keycaps have steep, straight sides. They fit well into the cutouts in the panel. On the asr, they move straight down onto the plunger, hitting switch reliably and squarely. However, there is much more play in my MP-7’s keycaps!

Each keycap has four bosses that hover about 1mm over the PCB. When I press a key, it can wobble in any direction. See demo video here Not only is this an unpleasant user experience, but I believe it’s stressing out the switches and causing accelerated failure. My video shows them outside of the panel, but inside the panel, is still a great degree of play. The measurements/design just aren’t as tight as on the ASR-X.

Any thoughts on this would be appreciated.

2

hiya just a small update on this. I made some measurements and attempted to lay a soft padded bed of material below the front panel switches (since the long bosses on the switches aren’t long enough to make contact with the PCB) so they wouldn’t rock so far in all directions, and lead to the quick demise of the switch… I tried some springy medium-absorbent foam, but haven’t been able to get the proper thickness of material. 1/16, to my surprise, is too thick. It’s so thick it’s hard to press the button.. Force from compression foam has a little more resistance than the original button! I tried to just place it on opposite, or side corners. That works halfway: it’s easy to press(good), and the travel is constrained to one axis(good) and it puts a little less stress on the shaft of the switch, but still much more than is desirable imo.(bad). I still have a few tricks up my sleeve, and it’s been fun getting into the lore of the MP-7. There are some cool SIMM ROMs people are collecting.. I think most of the Proteus SIMMs are compatible. Also they way they made the drum step sequencer is kind of neat. It’s button-per-step for the 1st 16 steps, then you “shift” ahead for the next 16-48 steps with dedicated buttons. Also, the buttons are in a 2x8 setup. Many interesting features on this device.