Hello Keith I have used an extra long repetition spring regulating tool which I got from Yamaha (Schaff also sells this tool). Might I suggest an alternative though. Remove the action and secure it in an action cradle. By rotationg the action until the weight of the butts are just supported by the springs. Any weak springs will show up by the fact that those butts will not be at the same level as the others. By shifting (rotating) the action further, you can also check for any that are too strong. This procedure will eliminate the need for a special tool as well as the inprecision of trying to adjust springs with no reliable test as to the real strength of the spring. Hope this helps!! Brian De Tar "NO OBSTACLES...ONLY OPPORTUNITIES" BDeTar@yamaha.com P.S. Yes, this is a new address. I am now an "official" employee of Yamaha.
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