Sticking Key Problems

[Bill Ballard]

At 9:50 PM +0200 12/14/02, Brian Lawson wrote:
>Hi, if you take some keys out and activate the action with your finger is it
>still sluggish? else, is the front rail pin going too far into the mortise?

Brian is getting you started with troubleshooting. I'd:

1.)  put your hand on the backsides of the keys in an offending 
neighborhood (a better way to set them aside in the troubleshooting 
isolation), step on the sustain pedal (to remove damper spring 
pressure), and with the other hand, lift the wippens from the 
front-side, remove your hand and watch the wipps and the hammer butts 
drop back. That'll tell you that the problem is not in the keyboard 
or the damper levers.

2.) Lift a set of wipps part-way up (half-blow for the hammerheads) 
with one hand and with the other, gently push the hammer heads the 
rest of the way up to the strings. Now let the hammers fall back, and 
watch for sluggishness there. That is the second half of the hammer 
blow, where gravity has the least effect on tier return. You can do 
the same test for the first half. Either of these will now eliminate 
the hammer flange pinning as the source of the friction.

3.) With the sustain pedal on, hold a section of hammers up to the 
strings, with the other hand, lift individual wipps until the jacks 
hit the butts, release and watch for slow returns there. This tells 
you it's in the wipp flange pinning.

4.) Key friction is checked with the action out. First the front 
bushings: check for at least 1mm of lateral play with the key at rest 
*and* at the bottom of the dip. The center bushings should also have 
that same side-play. Better yet, lift the key perfectly parallel with 
the balance pins. After 3/8"-1/2", the mortice will clear the pin. 
Now how does the  lift of the key feel (once cleared the center 
bushing). Continue lifting now that the only remaining sliding 
contact is the pin in the balance hole. How much lighter does the key 
feel once you've finally lifted it completely off. (Another test for 
the balance hole friction, assuming center bushing friction is fine, 
is lifting the key at rest from the front 1/8" upwards off the 
balance rail felt punching. Does the key fall back of its own weight?)

You'll see buzzards circling overhead when the friction is not in the 
individual components but in their combination.

Bill Ballard RPT
NH Chapter, P.T.G.

"When you do, you will"
     ...........Albert to his charge Chris, in "What Dreams May Come"
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