Piano Disc pedal mechanism problem

[Dean May]

HI John

First, make sure the pedal solenoid is properly adjusted. On a grand the
first adjustment to make is the amount of damper lift. This is done by
adjusting the large nut on the end of the rod sticking out of the solenoid.
Pull down on the rod to manually lift the dampers. The bicord wedges should
just be below the top of the strings- you don't want them coming above the
strings. It is important (critical) to minimize the amount of damper travel.
Make sure that the lever does not hit the stop screwed into the keybed above
the pedal lift rod. You definitely do not want the solenoid jamming the
lever against that stop. That will create its own noise. 

Once the damper lift is set, tighten the jam nut. Then you must adjust the
lost motion. This is done by turning down the stop at the top of the
soleniod. There is a jam nut on the top. Loosen it then you can turn the
threaded rod to raise or lower the stop. Lower the stop until the dampers
just start to ring, then back off a little. You want very little to none
lost motion. Then tighten the jam nut on top.

Doing these adjustments will set the trapwork to the absolute minimum travel
and may eliminate any noise. If the noise persists you must determine if
there is anything hitting at any point along the trapwork. Often the passage
for the lift rod through the keybed is narrow and sometimes there is
interference there. 

Another thing to check. I've seen this on Young Changs. There is an
extension off the backside of the keybed that the trapwork pivot brackets
are screwed to. I have diagnosed wood on wood knocking noises coming from
that extension. As the solenoid engages it loads up the trapwork creating a
bending load on that extension. After seeing that happen I made a design
change to all future Young Chang installations. I simply use a 90 degree
mending plate bracket (available in all hardware sections) to rigidly anchor
the backside of that extension to one of the beams, preferably as close to
the trapwork pivot as possible. Then make sure that the large screws holding
the extension to the keybed are really, really tight. You might even need to
take the extension off and use some urethane glue to secure it in place. 

Hope this helps. 


Dean
Dean May             cell 812.239.3359
PianoRebuilders.com   812.235.5272
Terre Haute IN  47802


-----Original Message-----
From: pianotech-bounces at ptg.org [mailto:pianotech-bounces at ptg.org] On Behalf
Of John M. Formsma
Sent: Tuesday, November 14, 2006 9:27 PM
To: Pianotech List
Subject: Piano Disc pedal mechanism problem

Piano Disc in a 1995 Young Chang G-150. (I'm assuming the PD system is about
as old as the piano.)

When the system is playing the piano, the sustain pedal makes a knocking
sound. It's more like wood-on-wood or wood-on-metal than a clicking
metal-on-metal type sound. The pedal doesn't have this noise during normal
human play.

I know little about PD systems except for the obvious things like
reinstalling actions, basic electronics, etc. After 15 minutes of peering,
replacing a worn felt, and head-scratching, I told the owner I'd ask others
rather than learning with her $$.

As far as I can tell, the problem is not in the "actuator" that engages the
pedal. (I did replace the felt under the actuator rod, so that can be ruled
out as a source of noise.) The noise seems to come more from the rod that
goes up from the PD pedal bracket into the action cavity. 
There is a rubber washer under the nut on the threaded rod that could be
worn, but since I don't have those, I didn't attempt a replacement. 
Moving the PD pedal bracket slightly did lessen the noise, so I'm wondering
if something is out of alignment. But nothing looked obvious.

Anyone know what this noise might be from, and how to tell a non-PD tech how
to fix it?

Thanks,
John Formsma