Ferrite core H-size question

[moshpit]

I have this Toei TC-HV25LM chassis that comes with a h-size ferrite core coil. It doesn't seem to be broken. I can see the screen move a tiny bit when I adjust the poti. But width gain is minimal. Do I have to turn this thing quite a few times to fill more of the screen? Or will I break the coil? I've found this on the interwebs: http://www.aussiearcade.com.au/showthre ... post783764

Maybe Grant can give a little bit more insight about how these things work.

[grantspain]

ferrite coils are fine adjustments,you never get more than a few cm's
if you have a width coil then you are likely to have width jumper as well

[PrincessPrinPrin]

Do I have to turn this thing quite a few times to fill more of the screen?

Yes, they're not like pots. To obtain the maximum inductance value, the core needs to be exactly in the middle of the winding and you need lots of turns to move the core, just like a threaded screw. And if you keep turning past the peak point the inductance value will decrease. The width range is very limited though, i.e. not the same as a width pot (where you have one).

[moshpit]

Thanks for your input! This helps understanding it a bit better!