[CAUT] Diagnosing bridge pin problems

[Ed Sutton]

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Cy-

You seem to have found something new and interesting!

You wrote "I pushed backwards on the top of the same bridge pin, and the note cleaned right up.  The strings were going flat because of loose bridge pins!"

I've not heard this mentioned before as a cause of pitch fluctuation, but it makes plenty of sense.

As far as pressing bridge pins go, I would press them any way that works to stop the beat.  It is also possible to rotate them to get a fresh surface next to the string, and in Yamahas I have pulled the pin and turned it over. Perhaps someone else has better advice.

You may need to loosen the strings to clear away and see what's happening at the bridge pin.

If the string is pressed into the wood in front of the pin, ot is probably losing power.  My sense is to reset the pins into the bridge with CA glue or epoxy, recutting the notch if needed.

Don Rose probably has some experience with this.  ;-)

Ron Nossaman has done research into what happens where the bridge cap, pin and string come together, perhaps you can attend one of his classes on this.

Ed S.

----- Original Message ----- 
From: Cy Shuster 
To: College and University Technicians
Sent: 4/17/2005 8:46:16 PM 
Subject: [CAUT] Diagnosing bridge pin problems


I'd like to know more about how to diagnose bridge pin problems.  Ed, this is the answer I tried to get on the Pianotech list with my question about seating strings, because I heard so many different things in the process... thanks!

I've been graphing the starting pitch of pianos ever since I began tuning for money, usually just sampling every A.  It helps me communicate to the customer what work needs to be done, and records whether the piano is stable or not.

Well, I've finally uncovered a problem by doing this!  I've now tuned the same C3 three times in this current concert series, and the second and third time the piano's been within a few cents of where I left it, except for a 10-cent dip between A5 and A6.

Checking it out closely today, I could see no damage to the soundboard, ribs, or bridge in that area (which I suspected because the problem occurred over a range of notes).  As I fine-tuned, I noticed that the problem was discontinuous, though: not every string was off by that much.  Listening to just a single string, I heard false beats, and so tried pushing down on the string just in front of the speaking-side pin.  Naturally, it went sharp!  :-)  I pushed backwards on the top of the same bridge pin, and the note cleaned right up.  The strings were going flat because of loose bridge pins!

So, what other tricks are there to diagnose bridge problems?  I've heard of using vice grips (handy when the problem is in the low tenor on a "D"!).  Which direction should you apply pressure on the pin?  Aft?  Down?

--Cy Shuster--
Bluefield, WV
----- Original Message ----- 
From: Ed Sutton 
To: College and University Technicians 
Sent: Sunday, April 17, 2005 5:05 PM
Subject: Re: [CAUT] CA for loose pins on a "D"?



To find out if it is a loose bridge pin, mute off carefully to a single string and have someone play the note while you go to the tail of the piano and press on the pin with a screwdriver tip.  If the pin is loose, it should stop beating when you press the pin.
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