I have already talked about primary valves here; as well as the fact that (in a common double valve player stack) the primary board takes the “input” signal from the tracker bar hole, and amplifies it to the secondary valve chest.
The primary valves are simpler in design than their secondary counterparts, but just as important to restore correctly.
To dismantle the common style primary valve board, support the board with two other lengths of lumber (e.g. 2×4″ or similar), placed on the underside edges so that the bottom of the valves have a couple of inches of space underneath them.
Now you can go through and hit each valve top with a sharp and firm blow (but not too strong!), striking them with a small flat hammer or with a punch equal in diameter to the valve stem (driven by a hammer).
This should cleanly break the glue joint of the stem to the top of the valve, without causing damage to either (assuming the glue is old hot hide glue). The glue joint here is quite small.
Once the joints are all broken, remove the leather facings and clean all the valve facing surfaces.
Here is an image of that work in progress:
It is advisable to keep pairs of valve buttons (upper and lower) together.
The surface must be kept true, so don’t go overboard with the sanding, when lapping the surfaces. You need just enough to keep the surface true without making it mirror smooth, otherwise you are reducing the effectiveness of the new glue joint.
A medium grit sandpaper like 120 should do just fine.
Using hot glue, glue all the new facings onto the valves, without getting any glue on the business side of the facings, this is important!
Also important is to preserve the flatness of the facing surface, so it’s a good idea to press the surface onto plate glass or another dead flat surface immediately after the leather is glued.
Some primary valves (like mine) have cloth washers on the lower part of the valve, underneath the leather facing. It is probably a good idea to replace these (if they are in bad condition), simply because you will alter the valve to pouch gap if you remove these washers.
I used a circular punch set (very handy tool for player work) to make a new set of cloth washers, as seen here:
Once the valve parts are ready, set them aside for the moment.
Turn your attention to the board itself, checking that the top and bottom are still true and there is no damage or problems with the board. If warranted, reseal the interior channels with shellac, being careful to not get any on the valve contact surfaces.
Now it’s just a matter of regluing the valves back in place, with the right gap. This gap in most cases is 1/32″ or 0.79mm. You can make a regulation gauge tool from different rigid materials; John Tuttle’s suggestion was to make one from an ivory tail, so that’s what I did!
Before you begin the glue up, quickly check each valve pair that the top does not grip the stem too tightly (a little too loose is actually okay). If too tight, you risk having the leather stay compressed when you press the valve together, giving you a false reading on the gap.
Too little gap will starve the valve. Consistency is important as always!
Reglue the valves, putting just a tiny dollop of glue on top of each valve stem, so it spreads to make a small bead around the stem on the top piece. It really doesn’t need to be a lot!
Using your gauge, insert it under the upper facing, and press the valve together lightly for several seconds. Done! On to the next one. As long as you are consistent in applying pressure with your hand, your valves should all come out to be the same gap.
Once he glue has cured completely, go back and test each one with the gauge.
The valves should all accept the gauge freely, and offer the same amount of resistance when withdrawing the gauge. If there are noticeable outliers, break the joint and reglue with more care.
One last thing is to replace any gaskets on the underside of the valve board, which will contact the pouch board.
That’s all folks!