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<\/a>And so let\u2019s make sure it does what it needs to do.<\/p>\n
First get a suction supply going, to test. In a perfect world you have a test pump from an old reproducing piano, but barring that, a regular shop vac will suffice (it\u2019s what I used). Just regulate the suction so that you are in the 5\u2033 water range (a vacuum dial gauge<\/a> is good for this, or a home made water vacuum gauge<\/a>). I made a laughably cheezy regulator, with a clothes pin and some elastics, to hold a piece of tubing a little bit outside the mouth of the vacuum. MacGuyver would be proud!<\/p>\n The drawback to testing with a vacuum is the noise. Apart from being generally grating, it also makes it difficult to hear leaks when troubleshooting. But, we must use whatever tools at our disposal.<\/p>\n Hook up the suction supply to the appropriate nipple on the box (it should be the one that is not otherwise identified). Then run the following series of tests:<\/p>\n 1) Close off all 4 inputs (you don\u2019t need to tube to an actual tracker bar to do this). Is the system balanced? You should see the pneumatic cloth get sucked in slightly in the bellows, but other than that, they should stay pretty much where they are. More on that in a moment. Assuming all good, continue.<\/p>\n 2) Open the outer holes. Still balanced? Good!<\/p>\n 3) Open the inner holes too, all holes open. Still balanced? Okay!<\/p>\n These tests check the balance of the pneumatics, if the bellows list to one side or another, or if they are otherwise not behaving identically to each other, we have a problem! The problem is a leak somewhere, so you\u2019ll have to track it down and fix it. Do it now, show no mercy to leaks whatsoever. It will not ever work if it leaks, so if it means taking everything apart and checking each component separately, just do what it takes!<\/p>\n Once we have established balance in equilibrium, let\u2019s check it in disequilibrium.<\/p>\n 4) Close all holes again, then open just one outer hole. The bellows should track accordingly, moving smoothly in concert to one side. When you cover the hole, they should return to default halfway position. If they move quickly but don\u2019t return reasonably quickly, this is a troubleshooting tip, likely a blocked bleed. Try the other outside hole in the same manner.<\/p>\n 5) Same as step 4, but concentrate this time on only opening each outer hole (not at same time) just a little \u2013 halfway or less. The bellows should still react and begin to shift as soon as the hole is opened partially.<\/p>\n 6) Cover only the inner holes, and repeat steps 4 and 5, one inner hole at a time. The bellows should again perform the same way.<\/p>\n Assuming it does all these things well, you should be good. But if there is something which makes you squirrelly happening now, just check again and again, repairing if necessary, until it looks like it should.<\/p>\n One thing I noticed on my first attempts, was that the right pneumatic would noticeable jerk when getting suction signal. It is a quirk of the design that the pneumatic is only mounted on the shift box with a single screw. This is not ideal from a \u201cno motion\u201d perspective, so I had to dismount it (which ruined my gasket, it had to be cleaned off and replaced), then check for flatness, and then make sure the pneumatic sits perfectly straight on the box, supported equally on both top and bottom, when you glue (or shellac) the gasket back on.<\/p>\n Thankfully the pneumatic had an access port for the screw, so I was just able to open that up to pop off the pneumatic, I didn\u2019t have to ruin the the recovery job I had done.<\/p>\n This does remind me however, that there are possibilities for some real bouts of tedium and frustration when troubleshooting. What\u2019s more is that the closer you get to the end, the chances of time-wasting increase, unless you take the time<\/strong> to really check your work at every stage. I must repeat this mantra to myself constantly!<\/p>\n Here\u2019s a video of a testing session I did:<\/p>\n