Technical Library

EARLY PIANO VI: Viennese fortepiano action problems

V I E N N E S E F O R T E P I A N O A C T I O N P R O B L E M S	OBSERVATION	CAUSE	CORRECTIVE ACTION
	Metallic rattle.	Hammer shank is loose in kapsel.	Remove hammer shank and squeeze kapsel arms closer before replacing shank.
		Loose key lead.	Spread lead with hammer to fill cavity.
		Hinge pin is loose.	Refit hinge pin, or bend slightly to better fit barrel.
	Metallic click.	Faulty join between kapsel stirrup and shaft.	Replace kapsel, or repair by peening rivet tighter or resoldering kapsel stirrup to shaft accordingly.
		Axle is misaligned in kapsel dimples.	Remove and replace hammer shank with axle in correct alignment between dimples.
		Worn dimples in kapsel stirrup.	Flatten dimples or replace kapsel.
	Weak metallic flick.	Escapement spring is misaligned or dislodged.	Realign spring.
	Weak metallic flick.	Escapement spring is weak.	Increase spring tension.
	Scratchy sound on playing key.	Escapement spring is corroded and rubbing on track in back of prell.	Clean corrosion from spring or replace with fresh wire.
		Hammer shank is rubbing against broken parchment damper loop.	Reglue or replace broken damper loop.
		Adhesive tape used for regulation under key tail extends beyond side of key.	Trim tape.
	Wooden knocking sound or thunk.	Prell has sideways motion because of weak hinge.	Replace prell hinge.
		Base of prell has lost adhesion with hinge.	Reglue separated hinge area.
		Hammer is blocking on string.	Increase letoff.
		Hammer shank is hitting moderator batten.	Adjust moderator batten height or thickness at offending point.
		Hammer shank is hitting damper post on return.	Adjust hammer shank alignment or trim damper post.
		Hammer is hitting gap spacer.	Realign hammer.
		Damper wedge is hitting underside of damper assembly.	Adjust damper clearance.
	Rattle on playing key.	Key tail is loose between rear guide pins.	Shim or releather keytail to reduce clearance at guiding point.
	Wooden click.	Prell is bouncing back and hitting bellyrail.	Increase spring tension, or pad point on bellyrail with thin leather.
		Hammer loose on shank.	Reglue hammer.
		Damper jack is loose in guide.	Shim damper guide.
		Insufficient padding on damper lifter post.	Replace cloth on damper lifter.
		Damper jack loop is broken.	Replace loop.
		Hammer is being caught by backcheck at wrong point.	Adjust backcheck.
	Wooden click or knock on release.	Prell is hitting hard end of wooden beak.	Check to ensure sufficient overhang of beak leather.
		Hard glue residue at the end of the beak leather.	Trim glue residue.
		Escapement spring tension is too strong.	Reduce spring tension to be uniform with neighbours.
		Hammer is hitting hard spot on rest cloth.	Inspect hammer rest and remove any glue, or fluff cloth.
	Squeak on playing.	Balance pin is rubbing on key mortise.	Lubricate balance mortise with Teflon powder.
	Squeak on release.	Beak leather is not sliding with ease down face of prell.	Inspect face of beak leather for contaminants, or lubricate prell face as necessary.
	Odd buzzing or resonance on playing.	String tail vibrating sympathetically.	Find offending string tail and reposition listing cloth or insert additional cloth wedge.
		Insufficient downbearing at nut.	Adjust downbearing or replace string.
		Insufficient nut pin angle.	Ensure nut pin angles over string.
		Damper is not fully lifting from string.	Adjust damper clearance.
		Loose bridge or nut pin.	Extract pin and swell hole before reinserting pin.
		Foreign object on soundboard.	Remove foreign object.
		Soundboard is cracked.	Repair soundboard crack.
		Soundboard rib loose.	Reglue loose rib.
		String is vibrating against damper jack.	Adjust clearance.
		Part of the traditional frame and panel lid is vibrating.	Attempt to silence resonating panel with thin leather wedge to frame.
		Some other object in vicinity is vibrating.	Find offending object and remove.
	Odd buzzing or resonance on release.	Damper has dried glue on outside surface.	Remove dried glue from damper surface.
		Chamois has been entirely glued to damper wedge.	Reglue or replace chamois, only gluing along base away from string contact point.
		Damper is falling on a node point.	Slightly reposition damper or use longer wedge.
	Oinking sound on release.	Damper leather is hard or worn resulting in insufficient damping.	Fluff chamois with a needle, or replace chamois if necessary.
	Oinking sound on release.	Damper wedge is glued too tightly to block.	Loosen glue join so that damper can align itself between string pair on key release.
	Note does not damp when released.	Damper jack has warped or is too tight in assembly and is sluggish or has stuck up.	Inspect damper jack and ease.
	Note does not damp when released.	Damper wedge has become dislodged.	Reglue damper wedge.
	All notes ring on.	Damper assembly dislodged or not correctly aligned.	Jiggle knee levers up and down rapidly, or realign damper assembly.
		Damper assembly feet too tight in housing.	Ease damper assembly feet for sufficient clearance.
		Knee lever action sluggish or stuck.	Inspect and adjust knee lever fulcra and transmission points.
		Damper lifter transmission levers too tight.	Reduce screw tension on levers so they operate freely.
		Dampers worn.	Fluff chamois with needle or replace chamois.
		Stringband has dropped with soundboard.	Adjust overall damper assembly height to suit stringband.
	Hammer return is sluggish.	Key is actually sluggish.	Diagnoze and correct sluggish key problem first.
		Kapsel is too tight.	Reduce tension of kapsel stirrup on axle.
		Kapsel is contaminated with old lubricants or corroded.	Remove hammer shank to clean kapsel dimples and axle points.
		Axle points worn flat.	Replace axle.
		Escapement spring tension is too great.	Reduce spring tension.
		Beak leather is curling on return down face of prell.	Replace beak leather.
		Surface of prell is not smooth.	Lubricate face of prell with graphite or Teflon powder.
	Hammer remains visibly high on release.	Action is not fully inserted in instrument.	Ensure action is pushed fully back.
Gap has narrowed slightly.		Scrape rear face of wrestplank or nut in extreme treble for additional clearance.
Hammer head is loose on shank.		Reglue hammer head to shank.
Hammer has been recovered and rear of head is no longer in line with others.		Adjust thickness of hammer covering to bring into line.
Individual backcheck is catching hammer too high.		Adjust individual backcheck.
Hammer bounces or jumps, especially when played hard.	Hammer not being caught on backcheck.	Adjust backcheck so hammer is positively caught on descent.
Key grabs, requiring hard force to play.	Hammer is catching on backcheck on way up (very dangerous).	Adjust hammer alignment or backcheck so hammer rises freely.
Key played once and does not repeat.	Beak has broken.	Repair broken beak or replace hammer shank.
	Hammer shank has broken.	Repair or replace broken shank.
	Hammer head has fallen off.	Reglue hammer head to shank.
	Hammer is stuck in up position.	Diagnoze and fix hammer problem.
	The prell has dislodged or its hinge broken.	Realign prell, or replace broken prell hinge.
	The beak leather is flimsy and has curled down the face of the prell rather than slid under.	Replace beak leather.
	The beak leather is losing adhesion with the beak.	Reglue beak leather to beak.
Note sounds severely constricted.	Damper is not rising because of broken loop.	Replace broken damper loop.
	Damper is not rising because jack leg is broken.	Replace broken jack leg or replace damper jack.
	Damper is not rising because damper stool has dislodged from key.	Reglue loose damper stool.
	Hammer is blocking.	Adjust letoff.
Note sounds dull or less powerful.	Moderator is not fully OFF.	Turn moderator OFF or adjust OFF position.
	Hammer is striking through moderator cloth because individual head is out of alignment.	Adjust hammer alignment.
	Hammer is not striking all strings for that note.	Align hammer.
	Hammer face not level.	Align hammer.
	Hammer releasing too low.	Raise letoff.
	Too much leather covering hammer.	Remove a layer of leather, or stretch top layer tighter.
	Missing or broken string.	Replace string.
Note always sounds out of tune.	Twisted or otherwise bad string.	Replace string.

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