Two Notes for the Price of One
By John A. Tuttle
Hi Darrell,
My first inclination would be any of the junction blocks where the tracker tubes go through. Sometimes a "cross-leak" will develop especially if there is a screw close by. The most suspect area is the connection between the upper and lower half of the upper section.
I guess one question would be, is the problem bi-directional? (If opening "C" activates "D", does opening "D" activate "C"?) Another very important piece of information is Exactly which notes are involved. If they are adjacent, I would suspect wood or gasket leakage. If they are, in fact, separated by one note then I would be inclined to suspect a crack between the two pouch chambers.
Does it happen all the time? If you reduce the vacuum to minimum do they both come on with equal strength? And at higher vacuum levels?
Although it would be an odd problem, it is possible that the pouches are actually cross-leaking. Imagine that in the area where the two edges of the pouch touch each other, or overlap, that the glue on the pouch closest to the wood has come slightly unglued. When either note is activated, as the pouch puffs up, it "blows" some air under the edge of the pouch into the other chamber. If that is the case, then lowering the vacuum level to minimum would show that the offending note comes "on" slower even if only by a few milliseconds and visa- versa. Here again, I would use smoke to test. I'd blow smoke in one hole and see if it comes back out the other. I suppose you could do the same thing with air but it's hard to see air.
One last thing. Take a suck tube and place it over a known good note. Alternately suck and blow on the tube until you have a good "feel" for the resistance to air flow. Then try the same test on the bad notes. If the resistance factor is greater when you suck "out" than when you blow "in" (as compared to the good note), then the problem is most likely the seal around the pouch.
All this said, personally I would just remove the pouch board and physically examine the pouches to eliminate the possibility that the pouches aren't glued down well enough, first. You could also examine the gaskets and the screw holes at that point.
One problem just came to mind that caused exactly the same problem but the notes were adjacent, not separated by a note. If you have ever had to "repair" a stripped screw on the "j" block between the upper and lower half of the upper section, and you put something down the hole to "fill up" the space, there is a good chance that the wood cracked and pushed a bit of the wood into one of the tracker holes. To remedy this problem (which I've seen many times) I take one-third of the newer type plastic "Y" connectors (which are a few micro-inches larger that the standard tracker hole size) and glue it into the tracker hole on the pouch board. In this case, you have to remove the "j" block between the two halves of the upper section of the pouch board.
Well, that's all I have to say. Good luck and let me know how you make out.
Musically, John Tuttle
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