No subject

And here we are again.
This time I have an interesting issue about sound improvement by changing
the position of a back check. I learned this at my last course in
Hamamatsu.
It is as follows: a couple of days ago I was asked to go to a Yamaha
dealer who had a complaint about a new Yamaha S6 (the handmade Yamaha copy
of the Steinway B, for those who do not know) being too soft.
There was no power in it due to very bad regulation.
So first I checked the down weight, found it a bit high, and made the
action a bit faster so that the down weight was a little less (just a
little, mind you).
I then made a complete regulation from beginning to end followed by a
tuning.
The treble was OK now but the base was still too weak. I decided to use
the trick with the back check.
Here it comes:
Take the action out, put it on a bench or table.
Push down a key (belonging to the soft sounding part) very slowly, you
feel the motion of hammer drop (careful now) you keep the key pressed
down, you look at the exact space between the lowest point of the hammer
tail and the highest point of the back check.
How much is it? is it 3 mm (sorry again, darned europeans) is it more?
When the distance between these two points is more than 2 mm, screw the
back check one complete turn (360š) up.
In Japan every technician has a custom made hardwood pipe which fits over
the back check (a rectangular hole).
Put the action back. Now listen again, you'll be amazed! This one key
sounds better, it has more power than before!
Just make sure that the distance is not less, than 2 mm!
And if you have to turn the back check down, be careful, the metal thread
might break.
This is a very powerful trick!
Naturally, everybody knew this allready and therefore my question to yall
is:
What is the explanation for this???????
My teacher in Japan did not know. Nobody I asked here in Holland has an
answer.

WHO does?

PS. don't forget to check the hammer blow distance...


friendly greetings from:

André Oorebeek
CONCERT PIANO SERVICE
Amsterdam, the Netherlands
email: oorebeek@euronet.nl

ƒ  where MUSIC is no harm can be  ƒ
----------

Andre
	Here is an educated guess as to why changiing the position of the back
check results in a stronger tone.  Especially in the bass
	Assuming that when the note is played pp or p, or mp, the tone is there.
When playing  f or ff or stronger, the tone is  not responding.
	The theory is that the hammer shank bends more on a sharp blow, and this
flex causes the tail of the hammer to come in contact with the back check
on its way  to the string thus robbing it of power.  In the bass the
hammer is much heaver, consequently the flex is (should be) greater.  If
the action is on the bench, the travel of the hammer tail in relation to
the back check can be observed.  If it is "too close" hammer shank flex
might cause the tail to brush slightly against the back check during up
swing.
	Solutions, make sure the tail is square to the back check.  Make sure the
tail is the "right" contour, especially at the shank hole.  Adjust the
back check.
	In a new piano there shouldn't be any problems with  an improperly bedded
key frame, or warped action brackets, or warped hammer flange rails, or
stripped screw holes for the action bracket screws, misplaced action
bracket shims, there is not excessive play in the keys, especially end
play, etc etc etc.
	I like the "Hamamatsu Solution"  turning the backcheck up one turn.
	Hope you share more factory "secrets" with us.
	BTW does the Yamaha S6 Steinway copy use tubular action rails, and the
half moon balance rail bearing?

Richard Moody ptt