Warping Keybed

[Mike Bingham]

Problem: I've got a hotel in Central New Jersey which has an MX80 Disklavier
that 2 winters ago, the keybed, for lack of a better description, "lost its
dip". It was during a very freezing winter, which we don't always get here. At
that time, they called complaining that it wasn't playing properly. When I got
to it , there was little if any letoff throughout most of the piano...only in
the extreme ends. As a result, the hammer butts were bouncing on the jacks. No
backchecking, too shallow dip. I ended up shimming the balance rail and
releveling to increase the key height back to a playable condition.
I suspected that the moisture content of the keybed was goiing thru this sponge
effect from Summer to Winter which is not unusual here, but I wasn't able to
measure or determine at that time exactly what had happened to the keybed itself
except to say that it hadn't come loose from the sides.

Well I just received a call from them, and they now say the piano barely plays
until it has warmed up for awhile. And then its not as loud as it should be.
That's the current complaint. I'm pretty sure it's not an external power supply
problem because we DID have that problem, but (presumably) this is on a surge
protected circuit which has no other possible interruptions.

I suspect that the keybed has shifted radically again and has introduced enough
lost motion to make it barely play-backable. Any ideas?? And what would account
for the increased volume after it has warmed up for awhile? Anyone out there
with similar MX80 problems? Unstable keybeds??

Any ideas welcome.

Mike Bingham,
Disklavier/PianoDisc Technician
Toms River, NJ