Kurzweil is a music systems company that manufacturers synthesizers and electric stage pianos. To approximate the dynamics of an acoustic upright piano, Kurzweil electric piano keys are weighted. This makes them touch-sensitive and enables you to play the keys softly and loudly. Each key has its own weight, which is connected to an electronic contact board. If you are experiencing motion or sound quality issues when playing certain keys, you may need to replace the key weight.
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Things you need
- Electrical tape
- Phillips screwdriver
- Silicone rubber glue
- Small bench clamps
- Cotton cloth
- Contact cleaner
Turn the keyboard volume down to zero. The volume on Kurzweil pianos is controlled with a vertical slider above the keys, to the left. Play each key in succession and listen for rattling. This is a sign that the weight inside the key is loose. If you don't hear any rattling you can rule out loose key weights.
Turn the volume up so you can better hear differences in the key dynamics. Play each key in succession again and stick a small piece of electrical tape on any key that is quieter than the others. It's rare that all of the key weights will be faulty at the same time. If the key weight is damaged, it can affect the movement of the key. There are two key contacts per key. One is triggered as soon as the key is pressed, and the other when the key comes to rest. The on-board processor takes these two triggers and calculates the velocity that the key was struck with. If the key weight is obstructing the movement, this calculation will be incorrect and the sound may extremely quiet or non-existent.
Unplug the keyboard. It's only safe to unscrew the keyboard chassis when the power is off.
Unscrew the top panel of the keyboard to access the key assembly. The number of keys depends on the model. The Kurzweil SP4-8 has 88 keys.
Lift up and remove each key that you marked with electrical tape. Tap the key against the side of your hand. A loose key weight will rattle inside the key. A completely disconnected key weight may slip out. If it comes out, coat the top in silicone rubber glue and push it back inside the key. Use a small bench clamp to hold the key weight against the inside of the key for an hour so that the glue sets properly.
Spray a plastic-safe contact cleaner onto a clean cloth. Lift up each key and wipe away any grime from the key contact. If the key contacts are dirty, the grime can interrupt the contact between the key and the key contact. This will affect the volume and dynamics of that key.
Replace any key weights that are chipped or cracked. It's rare that this happens, but if you have recently moved the piano, loose weights may have slid around. If you can't source a replacement, take the key weight out of the least used key, normally the lowest or highest key, and use that.
Tips and warnings
- Place the screws on a piece of electrical tape. Stick them down in the order that you removed them.
- Performing your own repairs may void the manufacturer warranty.
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