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
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