Quote:
Originally Posted by vts1134
The coil is right on 35 ohms. Should it change impedance when it is adjusted though?
|
Yes, it would if you measured it correctly.
If you measured it with an ohm meter, it would not change the value.
Confused?
Lets start this topic over again:
>>> Originally Posted by vts1134
In the meantime my question du jour has to do with L18, the horizontal size control. The schematic calls for an impedance of 35 ohms. It doesn't give it a value range though. Would 35 ohms be on the high side, or low side? The reason I ask is that my horizontal size control is at 3 ohms and spins, but does not adjust in impedance. Obviously broken . . . . . <<<
>>>Originally Posted by earlyfilm
Are you confusing impedance with resistance? If not, how are you checking inductance?<<<
>>> Originally Posted by vts1134
I'm not sure what you mean here, so I probably am.<<<
OK, let me ask a similar question in plain language.
If you have a coil of wire and measured the resistance and you and got, say 35 ohms.
You then measured the resistance with a powdered iron core inside it, the coil would still get 35 ohms.
You then measured it with your finger stuck through it, it still would read 35 ohms.
Why, because your VOM / VTVM measures your coil using simple direct current.
Do you agree?
Now, impedance is just the alternating current measurement of inductance with a few capacitor variables thrown in for good measure.
Inductance measures alternating current resistance, in this case, a very high audio frequency of just over 15,000 cycles per second (or Hertz.)
When the powdered iron core is inserted, the alternating current resistance (inductance) increases, but the direct current resistance remains the same.
Now about sticking your finger in the coil, is unknown, but it probably would raise the inductance, but not as much as the powdered iron core. However, depending on voltage involved, I must might not wish to test it that way. :-)
On the other hand, if you stick a brass rod in, it will lower the impedance (but not below it's direct current value).
OK, now your horizontal coil ain't nothing more than a coil of wire with an adjustable powdered iron core inside, and a capacitor connected over part of it or in resonance with it.
If you measured the horizontal coil with an ohm meter, just like my example, it too would not change.
How did you measure the coil?