Why So Many Tuning Coils Open

[rcewilson]

I don't work on these often but someone brought me a Mark II 73 Note Stage Piano with no output.
I find many many coils open.  In 4 places I added jumpers where all 3 coils in parallel were open to get continuity at the RCA jack.
It had sound on some keys but many were weak and I suspect those are open coils too.   I once looked at a 54 note version that had over 10 open coils but this is worse.
These are the coils with the white tape. 
I don't understand  how so many can be open and don't see how a repair can be justified. 

Bob

[pianotuner steveo]

Unfortunately ,this is very common. Especially with the white tape pickups. You either need to replace them, or rewind them yourself....

[The Real MC]

The coil wires are very fine copper wire and subject to corrosion.  They are coated to prevent corrosion.  The most common point of breakage is at the terminals, because the coating is removed so that the coil wire can be soldered to the terminal.  I had a few broken pickups on my sparkletop that I fixed simply by unwinding the loose coil wire one revolution and soldering it to the terminal.

As for the pickups with white tape, my guess is the coil wire is an alloy that may be more vulnerable to corrosion and breakage.  The alloy may have been cheaper and CBS/Fender/Rhodes was always looking for ways to make their products cheaper.

[David Aubke]

The coil wires are very fine copper wire and subject to corrosion.  They are coated to prevent corrosion.  The most common point of breakage is at the terminals, because the coating is removed so that the coil wire can be soldered to the terminal.  I had a few broken pickups on my sparkletop that I fixed simply by unwinding the loose coil wire one revolution and soldering it to the terminal.

As for the pickups with white tape, my guess is the coil wire is an alloy that may be more vulnerable to corrosion and breakage.  The alloy may have been cheaper and CBS/Fender/Rhodes was always looking for ways to make their products cheaper.

I agree that the problem usually manifests right where the magnet wire attaches to the soldering lugs. Unfortunately, though you'd expect a 50/50 distribution between breaks at the start and end of the coil, it always seems to be broken at the start - the part that ends at the center of the coil - so you can't just unwind a wrap and re-solder.