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While installing a replacement Aeolian block valve is a relatively simple job, removing the old block valve can be a real 'pain in the neck' (literally as well as figuratively). The heart of the problem is that the block valves were glued in place with a Duco-type cement, and the only way to get the blocks out of the piano is to break them out. Since the block valves are made out of hard plastic, there are a number of precautions that should be taken to avoid injury to both the piano and the person doing the job.
To avoid personal injury, I highly recommend the use of safety goggles. Pieces of sharp plastic and glue will be flying around. I also recommend the use of a very bright, stationary light. A flashlight simply won't be adequate. To avoid injury to the piano, follow the steps below.
Removing the Block
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1. Disconnect the tubing that goes to the blocks in the area around the defective block. To insure that those tubes get back where they belong, it is wise to label them clearly.
2. Using a piece of paper or cardboard, cover the exhaust ports (or the tops) of all of the blocks in the surrounding area.
3. Using a sharp chisel or putty-type knife, break the glue seal on the side of the block. Clear away the glue until you can see the wood.
4. Using a blunt piece of metal or a piece of hardwood that is about the same width is the block valve and a hammer, tap firmly on the front corner of the block at about a 35 degree angle.
5. If the block seems quite resistant to coming loose, try attacking it from the opposite side. If it is still reluctant, hit it harder. Word of caution!! DO NOT UNDER ANY CIRCUMSTANCE USE A LEVER TO TRY AND PRY THE BLOCK LOOSE. DOING SO CAN ONLY CAUSE POSSIBLE DAMAGE TO THE ADJACENT BLOCK - AND THEN YOU WILL HAVE TO REPLACE TWO BLOCKS INSTEAD OF JUST ONE. ALSO, AVOID HITTING THE BLOCK FROM THE TOP OR THE BOTTOM. DOING SO MAY CAUSE SERIOUS DAMAGE TO THE WOOD. With patience and persistence, the block will come loose. Sometimes it will come loose in layers. That is NOT a problem.
6. In some cases, small pieces of plastic will break away from the block and stay glued to the wood. If that happens, gently chisel off the remaining pieces until the surface area is 100% clean. (Take care -- Those chips will fly!!)
7. If you are very unlucky and a little chip of the wood comes away with the plastic, don't be too concerned. If a large chip breaks off, save it!
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Installing the Block
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1. The recommend method of installing the replacement block requires the use of a hot-melt glue gun. It doesn't have to be a fancy industrial model. A simple craft-type glue gun will be adequate. Be sure to use clear or yellow type glue. Do not use the white, caulking type glue.
2. The only word of caution is be prepared to move quickly. Once the hot glue is applied to the block, you only have a few seconds to put the block in place. It might be wise to practice putting the block in place before you apply the hot glue. That way you'll know where your hands and eyes need to be to put the block in place squarely and evenly.
3. Using the special pattern shown below, draw a bead of glue onto the block in one even sweep. Failure to do so will result in high or low spots which can cause problems. If necessary, practice the pattern a few times beforehand. The bead should be just wide enough to cover the plastic edge in the middle of the block. Also, take care not to overlap the bead at the beginning or the end of the pattern.
4. Now, gently put the block in place and press just hard enough that you see the glue start to squeeze out around the sides. Sometimes it's easier to look through the block at the bead that is squeezing out from the middle layer. Whichever way is more convenient, do it that way. The point here is to press the block in place just hard enough to get an even layer of glue between the block and the wood. Pressing the block in too hard can cause so much glue to squeeze out that the intake and exhaust vacuum ports will become too small, and the block will not work proficiently.
5. Hold the block in place for at least 10 (ten) seconds. The glue will set very fast.
6. Remove all protective paper or cardboard. Reconnect all tubing. Test the replaced block.
7. If by chance you place the block in crooked, DO NOT ATTEMPT TO STRAIGHTEN IT OUT. REMOVE IT IMMEDIATELY AND WAIT UNTIL THE GLUE HAS COMPLETELY COOLED. One of the beauties of this installation method is that it gives you room for error. After the glue has cooled, it can be easily removed from both the block and the wood with very little effort. Normally, it will pull right off like a gasket. Occasionally, it will be a little more difficult to remove from the wood, but generally this only happens if the block was pressed too hard into place initially.
8. If this procedure is followed accurately, the block will be firmly in place for life, it will have a perfect seal, and it will work exceptionally well. Failure to follow the above instructions may lead to a myriad of problems.
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