13 Mar
2008
13 Mar
'08
11:42 a.m.
On Wed, 2008-03-12 at 23:23 +0000, Tony Duell wrote:
I think you misunderstood me. I've seen many linearity coils with
permanent magnet bias -- they turn up in most monitors. In fact I just
have to look on my bench now to see the monitor PCB from an HP9826
machine [1] to see one of these devices.
What I have never seen is one with a '+' marking. Of coruse they're
polarised (getting them the wrong way round gives an 'interesting'
display). Most of the time they are physically unsymmetircal so that they
either only fit the right way (a third offset pin so the PCB pads will
only take the compoennt one way round) or at least you can line them up
with the silk screen.
[1] THis 'monitor' PCB contains the video amplifier and horizontal
deflcition circuits only. The vertical yoke connections go via varios
connectors to the text video PCB which also contains the vertical
deflection circuit.
The only thing is, I've never seen one with a
polarity marking (often
they pnly fit the PCB one way round), and they're normally larger than
the comopneent you show.
I'm surprised at that - they crop up in monitors a lot, usually where
they linearise (or non-linearise) scan waveforms.
The magnet gives the coil slightly different properties depending on
which way round the current flows.
Exactly.
-tony