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Im working on this Yamaha C108 it had several broken bass strings (is curious, another Yamaha M404 had almost the same broken bass strings. They both had the same frame and string length, it was easer to make the bass strings cause were identical. how that can be?

Any way, while looking it the C108 I notice that the middle tenor section from F4 to F6 had been replaced before, I notice it because the replacement was made so bad, the pin wasn't turn out to install the new string the new coils are touching and compressing the wooden bushing, I try to figure out why this person did that and i notice that the scale on the piano has something wrong.

I decide to measure all the strings and i notice that the scale written on the bridge is different from the one it has. The wire numbers on the bridge start on 18, but the strings at 17.5 and so on, all wire sizes are half thiner of what it said on the bridge, but the ones that have been replaced follow the bridge guide, so it has a double section of 16 and double section of 15 is a mess.

Other than the ones replaced, are factory installed so what went wrong at the factory the guide stamp on the bridge or the wire installed.

The best probably is to take out the replaced wire and continue with the factory scale ignoring the bridge guide, just following the logic of the scale, the points of where the size change are the same.

Or have the piano re-scale and restring it all off course keeping the bass strings

Since the M404 seems the same, I´ll look at the scale to see if is different or has the same issue, the bridge guide has the same wire numbers and it change at the same points but i didn't measure the strings


Any comments

Thanks a lot

I think that Japanese metric wire sizes might be a half-size different from ours. Check by measuring a new piano (or one you know hasn't had strings replaced).

--Cy--

There is a machine that winds the string on the pin and inserts it onto the block.

I don't know if Yamaha is using one of these or not.

It is possible that the metal piece that holds the wire on the pin is improperly adjusted and slightly damages the wire where it wraps around the pin.

This will cause sections of notes to break at the tuning pin.

So the question is, where is the string breaking? If at the pin, a magnifying glass could reveal a crimp in the wire at the break.

There would be no need to adjust the scale if this were case.

Even so, the most effective solution would be to change the speaking length .... not really an option here.

They break at the end of the loop, what I was thinking is that when they finish the loop the wire got damage the funny thing was that, in two yamaha were the same note or string number that broke.

Also i check another yamaha same size and all wire is half size thiner so you might be right about they have a different metric size. Im already replace the wrong wire following the lead or the original wire and sounds much better now also i got all the pins back to the same alignment.