First of all- Experience tells me that any Conn horn with 10 years of use on it is ready for a valve rebuild. We almost never see horns that have had consistently good maintenance, and corrosion, not wear, is what prematurely destroys valves.
The best (and only) way to accurately determine valve condition is by static air testing. A column of air at a known pressure is created in the instrument and the "bleed" is measured. While it is possible to isolate valves and test them individually, the sad fact of the matter is: if one leaks, they all leak. (I'm talking about normal deterioration here, not the result of damage.) The valves need to be clean and normally lubricated for this test to be accurate. Many horns loose 20-30% of their compression after a cleaning. It is possible to measure the acoustic impedance of an instrument and, by comparing it to a plot of a horn known to be tight, to get an idea of the relative deterioration of the playing qualities. The least useful method of testing is the "pop" test. You pull the slides, wait a few seconds, and depress the valve. No pop is bad, a loud pop is good, and anything in between is indeterminate. I hope this helps. Bob Osmun www.osmun.com -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of paxmanhorn Sent: Friday, February 28, 2003 12:26 AM To: Horn List Subject: [Hornlist] Horn Related!! Please read me!! Hello all, Been a while since I've posted anything, mostly because I haven't had anything meaningful to contribute, but partially because I've been too busy clicking my 'delete' button to get rid of all these extra NHR messages. Whew! We can really go crazy with our blustering opinions, can't we? Anyway, I have a question. I have heard much talk in the past about 'leaky' valves and am at a loss to remember the correct procedure for determining whether the valves on a horn are tight or leaky. Could someone please give me the proper way to determine this? I play a Paxman model 20 and have no need for another horn, but a friend is thinking of purchasing an older Conn 8D and the valves are suspect. It plays ok, but it 'feels' funny to me, and I want to be sure not to give inadequate advice, so I could use a little training in leaky-valve-detection. Thanks in advance, Carl in Abilene, TX _______________________________________________ post: [EMAIL PROTECTED] set your options at http://music.memphis.edu/mailman/options/horn/rosmun%40osmun.com _______________________________________________ post: [EMAIL PROTECTED] set your options at http://music.memphis.edu/mailman/options/horn/archive%40jab.org
