xwhatsit compatible solenoids for $10
Found a good replacement for the standard beamspring/model F/model C solenoid that's cheap and works perfectly with a couple minor mods.
Best first thing about it is that it has an adjustable throw. Default is around 4mm or 5mm. But with a couple minutes with a dremel or rat tail you can elongate the adjustable channels to shorten it to whatever you want. I put it about at 1.5mm to give some space for a second small mod you'll need. But you can change it to whatever you like yourself.
Resistance is almost exactly the same as the the ibm solenoids so you don't need any extra power resistors. Connector is the same pitch too.
For the center plunger, you'll need to remove the washer it comes with just so it doesn't rattle. Replace it with an O-ring to silence it on the return stroke and keep it from double tapping against the frame. You can use normal thick soft keyboard O rings for this. This further reduces the stroke so be sure to account for it when you put it all back together.
It has a brass plate mount that can be bolted, taped, or glued to any substrate. In more cramped keyboards, you'll probably need to take a few minutes and cut the flanges off of it.
That's it though. No fuss no muss and sounds good. Outside the cases, they sound basically identical when I tested both with a 9V battery. What you hear in the video is basically acoustics of the cases and linear versus beamspring. You can also set the timings a tad lower since the modern one uses better magnets. The solenoid itself is basically the same size, but the frame is bigger on the new one as well.
http://www.ebay.com/itm/0837L-06C20-6V- ... 1967978003
https://www.dropbox.com/s/avfahxa7icbrk ... t.mp4?dl=0