This unit was suffering from multiple dead keys, and things had been getting progressively worse. There were other mechanical issues, and once they were resolved the electrically dead notes could be focused on. By tapping the coils center pole 12 pickups were found to be dead, and on removing one it could be seen that the inner end of the winding had rusted through where it meets the pin. There is not enough wire left exposed for me to attach a bridge wire to, so the coil was deemed beyond repair. As I researched the Rhodes Mk 1 Stage 73 I found out just how big a problem that rust on the coils was, and that most used parts on Ebay etc are remnants of machines scrapped due to this problem, with statements in the ads like “rust cleaned off”.
As stated earlier, 12 coils were oxidized through, and looking with a bright light and magnifier 31 more can be seen to be in various stages of oxidization, so eventual failure of these coils is inevitable. I was unwilling to spend on this many used coils, knowing that while currently working, they may be no better than the other 31.
Further reading showed success with creating a machine that assisted with spooling the wire off a coil, removing the bad first 1″ of wire, then rewinding the coil. I set about creating such a machine, and after a couple of days of debug/prototyping I was able to succeed in the rewinding process. This process is still labor intensive, so not a push-button solution. I wrapped the coil in acid-free masking tape, rather than sellotape.
So little wire is removed by this process that the resistance of the coil is unaffected, and each coil was measured and in spec (184 ohms was typical). The coils were remounted in the machine, and no discernible difference between re-worked and non-reworked coils was found. The unit was tuned and is ready for the customer to check out, and decide whether to go-ahead and deal with the other coils before failure, or as they fail in the future.
I found this to be an interesting and well-written report, keep up the good work!