I was called to tune a Rosenkranz upright that has a strong buzzing when playing the first tenor unison.

After a quick search I found that the left and center strings of the unison actually touch the plate strut at the break when they are played.

I´ve put a piece of rubber between the left string and the strut, so the note can be played, only the center and right strings sound now.

This works fine for a piano or mezo-piano blow but if you play a forte or a fortissimo, then these strings also touch the strut and produce a very loud buzz.

This piano was rebuilt five years ago. New pinblock, soundboard cracks repaired, new hammer heads, new dampers, action refurbished, new strings, etc...

I guess it was when re-installing the plate that it landed too near to the soundboard and that's why the strings are too close to the plate.

What do you think is the solution to solve this?

Sould I shim the plate in order to increase the distance between the plate and soundboard/treble bridge? Or can I file the strut near the strings in order to make some clearance? Or maybe work on the bridge to lower the strings?

Any advice?

The easiest thing would be to file the plate.

how was the overall pitch? I seen cases like this and the cause was the pinblock was separated from back frame- everything moving forward causing the first tenor strings coming in contact with the plate

Another thing to just check, would be to make sure the strings are not actually buzzing on the bridge once they go past the hidge pins. Sometimes, once they go past the hidge pins, they are still engaging the wooden part of the bridge. This will cause funny buzzing sounds too. If so, you will have to notch out the bridge a little bit under the wires there so the strings are not touching the bridge at that point.

Otherwise, it shouldn't take to much to file the plate a little bit to eliminate the buzzing if that's what's happening.

But, as Wayne mentions, if there is another reason why it is doing this, you will have to ascertain this and possibly correct this problem to correct the other. Provided of course, the piano is worth it...

I am sure the strings are buzzing on the plate strut.

The pitch is right. I've tuned this piano last june and returned a few days ago to tune it again and it's on pitch. The pinblock is new and well glued to the back structure.

I have never heard about filing a plate and I was wondering if it was right to do it.

Thanks a lot for your answers.

Did it have this problem last time?? If it didn't, you have something moving. You might have some stripped perimeter screws or a nose bolt.

Yes it had that problem the first time I tuned the piano. I have muted the string waiting for a true repair.

I see. The strings are buzzing where they cross the strut that follows the lowest bass note, right?
Check the downbearing angles across the bridge. That note is at the edge of the soundboard so the bridge will almost show the true brige height unstrung. If the angle to the hitch pin is excessive, the plate is too low or the cap was put on without adjusting and is too high. Pull a string line from the capo across the cap. You should have about 2mm of height above the point on the plate where the wire contacts the bearing point on the plate.
The easiest is the file the plate just enough. Or you can pull the bridge pins and shave the cap down and renotch.
What do those notes sound like? Anything good?

Oh, what I wanted to say was if the angle to the hitch is NOT excessive then the top of the plate is leaning forwards and the thing has some structural problems behind the pin block.

In the 70's Baldwin made a bunch of SF10's with plate casting at the bass break where a decent strike would whang the plate. It was like a pile of cast slag built up right next to the plate, all finished nice from the factory. Had to file it down with a Moto tool.

Yes, I believe the piano has structural problems.

As I've said it was rebuilt 5 years ago, they have put a new pinblock and I guess they did a poor job reassembling the piano.

This piano is located 150 miles from Mexico City, so I should wait until next tuning to file the strut.

And if the piano has gone way flat and the third string is buzzing, RUN!!!! It's going implode.

Ask yourself why they called a beginner tuner from so far away....

Beware, give disclaimers in writing....

If the pin block has been put back wrong but is sturdy and not moving you can indeed file the plate strut, you can also tap the strings down with a screwdriver and pin-hammer where they emerge from the agraffe to get another half mm. Sounds strange but it works.

Tap down the strings(?) Never heard of it.

There are no agraphes, only V bar, must I tap anyway?

I am not affraid to be made responsible of any damage to the piano. I did not the rebuilding. I've only tuned it.

Whoops, as the strings come over the bar, at the very beginning of the speaking length the strings can indeed be tapped. It only works on newish wire and is really only to get all the strings in a trichord in line with eachother where there is a discrepency leading to toning problems. Sometimes the strings pass over a removable brass or even wooden rod that sits in a groove. In that case one can replace the rod for something thinner while the tension is off that section. That would take the strings down a bit but these are really things that I would bring a piano into the workshop to address. Sorry I can't be more help!

Thanks delacey,

I am waiting until next tuning to solve this problem, I guess the best is to file the strut.