F
Fred Abse
Guest
On Fri, 08 Feb 2013 16:32:40 +0000, Ian Field wrote:
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)
Also diode modulators."Fred Abse" <excretatauris@invalid.invalid> wrote in message
newsan.2013.02.08.12.20.33.475919@invalid.invalid...
On Fri, 08 Feb 2013 08:55:32 +0200, Tauno Voipio wrote:
The scan system is resonated on the third harmonic to the line rate to
create the S-correction for the scan, slower on the edges and faster at
the middle.
That's yet another version of the widely-held misapprehension about
horizontal output harmonic tuning.
The *leakage inductance* of the flyback transformer is resonated at
either the third (monochrome), or fifth (color) harmonic of the "flyback
frequency", which is the reciprocal of twice the flyback time, somewhere
around 3, or 5 times 50kHz for NTSC/CCIR 525/625 line TV, assuming 10
microsecond flyback.) This has the effect of flattening the peaks of the
(half-sine) flyback pulses, and can be seen as either one or two small
dips in peak flyback voltage. In early tube designs, this was done with
a small winding underneath the HV winding, which was resonated with a
capacitor. In later designs with diode-split windings, it was done by
carefully controlling interwinding capacitance.
That sounds more like what I (vaguely) remember reading about all those
years ago.
S-correction is a separate issue, achievable with a suitable capacitor
in series with the actual scanning current.
That's what I remember - E/W modulation was done with a saturable reactor
in the days of delta-gun CRTs, they developed H/V summing chips for
pincushion control in the inline-gun CRTs.
--
"For a successful technology, reality must take precedence
over public relations, for nature cannot be fooled."
(Richard Feynman)