Small Valve Boxes

The last component to rebuild on the “head” section is a small valve box which is a primary booster for the Theme signal. The “Theme” feature is specific to certain types of player pianos, I will explain about that later.
For now we just need to be concerned that it works, although there is not much to it; just a pair of primary valves and pouches, inside a small box.
As per other operations, take it all apart, use a screw map to stow screws, carefully take apart the primary valves by chipping away glue blob at the top of stem, then a modest but firm blow with a small hammer (and punch, if necessary). It will come apart in two pieces.
Pull off what gasket material you can by hand, then scrape until you are at the glue residue level. Then lap surfaces on sandpaper over flat glass (or other dead flat surface). You don’t need to go to fine on the sandpaper, 120 grit is fine as a little roughness will help the glue joint.
Once it’s all apart and prepped, you’re ready to start rebuilding, with fresh materials!

Now it’s time to measure, mark, cut and glue some new gaskets. I mentioned about gaskets last time, so the method is described there. Once it’s all cut, glue in place, using enough but not too much glue, applying quickly if using hot glue –as you should!
Pull the old leather off the valve facings, resurface the top face (the bottom should not have been glued, if Standard style), and put new leather facings on, being quite cautious not to get any glue on the outside of the facings, which will render them useless. Again, enough glue, but not too much.
Reassemble the valves on the top section, using a gauge to space the travel gap at 1/32″, the default distance for Standard style outside valves. John Tuttle gave me a tip that you can make one from an old ivory keytop tail, so that’s what I did! It works! A little dollop of glue on top of the button at the stem will keep it locked in place. It doesn’t take much.
Put the box back together. It may look something like this ( I haven’t fitted the dust cap, as this is cosmetic and blocks the view of the primaries for testing):

A small valve box with a double primary valve

Once reassembled, it’s testing time. You probably don’t need a suction pump from this, just a tube with mouth power (shallow breaths in!). When the valve is receiving atmosphere signal, it opens and let’s atmosphere pass to the output. When the valve input is closed off (meaning that there is roll paper covering the corresponding holes on the tracker bar), it should receive nothing, and therefore output nothing.
The inputs should be the lowest horizontal row of nipples on the valve box, so when those are plugged and unplugged under suction, they should pop up and down accordingly.
It’s a little cumbersome to check all this in tight quarters, with a noisy vacuum cleaner as a test pump, but it can be done.Once you’re happy with the performance of this valve box, time to move on. In my case it means that the head of the stack is done, yes! It’s a nice milestone to have the motor, transmission, spoolbox, tracker and valve box ready for final assembly. Now let’s dig into some peripherals!

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