[Argus25]

American RF coils in TV's are often quite different to English ones. In American sets there are often threaded brass screws attached to the ferrite slug with a thread and locking mechanism on the coil top.

In many UK sets, there are ferrite slugs in bakelite former . In the case of these never attempt to turn these with anything other than a plastic instrument. Apart from the fact a metal instrument de-tunes it, the metal vs ferrite contact puts extreme focal forces on the slot in the slug, and it will crack.

If it is just the very top near the slot that cracks, usually you get a second chance from the slot on the other side of the slug. If however the slug splits in two, it won't unscrew as it expands in the hole with any attempt to rotate it and the cracked edges bind in the thread.

Drilling out one of these slugs is not practical as the ferrite wont drill, the drill will simple decenter and damage the threads/former. It could be possible to use a diamond grinding tool. So if these slugs are jammed or tight, avoid to much force and use a combination of warmth to soften wax and melted rubber and wd40 to gently get them moving and only with a plastic tool, never metal.

One way to lock the ferrite slugs is teflon tape, but originally they often had a small rectangular section rubber cord, maybe only around 0.2mm to 0.3mm square. The trouble is this stuff melted or disintegrated with time, it was probably latex.

There is some fine white small diameter rubber cord available, it is found in flat elastic used in the waste bands etc of clothing, so you can get it from any sewing shop. You have to pick off the white fabric around it to get the thin white rubber cords out, it is perfect for locking slugs in UK style RF transformers.