If fixing the connections does not help, the only thing to do
really is take it out and rewind the coil.
There is a lot of information around on how to do that. Watch out especially
for sharp edges on the ferrite toroid; they can and do short out the wiring sometimes.
You can file the edges, but it is a real chore. If the toroid is big enough, some wind it first with
tape to blunt the edges. That does little to the inductance and can help in avoiding
scraping the wire.
Use new wire -- the old wire is suspect. Usually something
around #24 magnet wire is what is used.
john
AD5YE
