1) I used Ballistol-which is an all-purpose lubricant usually used for fine mechanical moving parts-I've had this for awhile and it is not petroleum or silicone based-is labeled safe for rubber, plastic and all kinds of metal and is an oil consistency rather than grease. I used it sparingly. Also is heat resistant and has properties that keep it from drying out and stays adhered to surfaces. So far it seems to be working, but with one other important detail which caused me to wonder whether the silicone based grease was the culprit after all. I'm not sure now, but i am thinking the rubber bumpers are also silicone, and this silicon grease may have soaked into the bumpers and swelled these up-causing no end of problems. I am only deducing this because-many keys that did not previously cause problems now were getting jammed up sliding up and down over the bumpers once i tried the silicone-based grease. I ended up completely cleaning the offending keys with dishwashing detergent and a small plastic scrub-brush, and the bumpers with alcohol just to make sure i removed the silicone grease completely before i tried the Ballistol. AND-AS OBVIOUS AT IT SHOULD HAVE BEEN TO ME.....
2) The real solution-was the fact that these bumpers once swollen, need to be trimmed back to fit under the key-not an inconsiderable task and frustrated me no end trying to sand and file off part of the left and right rubber edges-the parts that were binding-without any success. I reverted to my Swiss Champ knife with its very sharp and small scissors and snipped about 1/16" (1mm) off one end of each bumper that was binding, and this finally solved the problem. I had to do this with quite a few keys, that were binding even with the Ballistol. Probably could have gotten away with alot less Ballistol since I kept trying to solve this problem with lubrication, rather than using this simple fix from the beginning. Sometimes the most obvious solutions, the simple ones elude me. Not much to look at, but notice how much silicone bumper I had to remove from several really nasty keys-how tight these rubber bumpers were in the first place, through design I guess, or the additional silicone grease.
Was this all worth it? After all this time, just because Fatar's workers were drinking too much vino and munching provolone when they put some of these key assemblies together-cost me tremendous time and energy, just to correct an inherent defect that should never have seen the light of day. At east this TP20 does not have the inherent black/white key imbalance problem as did the original TP40.
