From: Martin McCormick <martin.m@suddenlink.net>
To: Microcontroller discussion list - Public. <piclist@mit.edu>
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Date: Thu, 26 Nov 2020 06:25:18 -0800
Subject: Re: [OT] Hyperikon Retrofit LED Tubes Without Ballast and
 fluorescent	lamps and TV!
Thread-Topic: [OT] Hyperikon Retrofit LED Tubes Without Ballast and
 fluorescent	lamps and TV!
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"Harold Hallikainen" <harold@mai.hallikainen.org> writes:
> On the TV fluorescent lamps, yes the frequency was much higher than the
> frame rate (though I don't remember what it was).

It could have been 40 or 50 KHZ and probably would have been just
fine.

> NTSC television is interesting! It's described at
> http://mai.hallikainen.org/org/FCC/FccRules/2021/73/682/ . Prior to color=
,
> the field rate was indeed 60 Hz, the power line frequency, to avoid
> rolling "hum bars." With color, it appears everything is based on a
> precise 5 MHz with the chroma subcarrier being 5 MHz * 68/88. The
> horizontal scan rate is 2/455 * the chroma subcarrier frequency. The fiel=
d
> rate is then 2/525 * the horizontal scan frequency. I think that the
> frequencies were chosen such that dots created by the chroma signal would
> be white on one scan and black on the next, letting the eye cancel them
> out. Similarly, the European PAL system switched the chroma phase 180
> degrees on adjacent lines (since the image is interlaced, perhaps this
> works out to just being a phase switch on each field). Chroma phase error
> resulted in a hue shift, but in opposite directions on adjacent lines. So=
,
> the eye averaged them out to avoid hue shift due to chroma phase drift.
> Clever!
>=20

>From 1981 until January of 1989, I worked as a technician in the
Oklahoma State University Audio Visual Center where we fixed a
lot of 16-MM projectors and some video equipment. =20

	One of our most interesting technical jobs was one we did
for a client who had a daughter who married a citizen of
Australia in the mid eighties and the family had a camcorder
that, of course, was built for the Australian version of PAL.

	The American members of that family, here, were eagerly
awaiting a new TV that that was available that would play videos
from about every standard available plus they had bought a
Panasonic VCR that would play everything, record most formats
except SECAM, but they still had no monitor.

	Their daughter and her husband bought a small monochrome
TV at a shopping center in Canberra and brought it all the way
hear, only to find that the VCR's remodulator wouldn't deliver a
signal on a frequency that the Australian TV would receive.

	What we did in the interim was to take a Commodore64
video monitor and adjust the vertical and horizontal hold to make
it sync up with PAL.  The lower vertical frequency of fifty
fields and 25 frames per second made for some overscan due to the
stronger magnetic field of the deflection coils at that frequency
but the picture was otherwise crystal clear except for no color,
Oh, I guess that's colour.


	I remember us commenting on the fact that it was June
26TH stamped on the screen of the recording from Australia which
was video of a local park as a little girl played outside.  In
the Northern hemisphere, this is normally a time of lush
vegitation but this was Australia and just at the start of Winter
so all the leaves were dead on the ground.

	I also remember examining the power plug of the
Australian set and noticing it was just like our power plugs
except that the two prongs are at 45-degree angles from each
other.  It was an interesting experience.

	We got the little TV to work by plugging it's mobile
power cord in to a 12-volt DC supply I had built that had a
mobile socket.

	The TV worked but I think the American side of the family
got their multy-standard TV and the little portable was
orphaned.


> On light flicker, movie projectors used to use an incandescent "exciter"
> lamp to light the sound track. Light would pass through the film to a
> photocell. At first, the film density was varied to carry the audio, but
> later the black to white area (width of a white or black stripe on the
> film) was varied to carry the sound. Of course, if the lamp was powered b=
y
> 60 Hz, you'd get 120 Hz hum in the sound. So, the obvious solution would
> be to run the lamp on DC. But, many projectors instead ran the exciter
> lamp on high frequency AC. There was a power oscillator to drive the
> exciter lamp.

	Ah yes.  I Believe that one of the Bell&Howel 50's-era
projectors like the 399AV had a 50C5 oscillator which performed
that function.  I personally thought that projector had some of
the best film sound.  There was even a little lever that tweaked
the focus of the sound optics.

> On the NE-2, one of my earliest project was an NE-2 based relaxation
> oscillator running off a B battery. Choosing component values, I could ge=
t
> a light flasher or get audio out of it.

	At around 20 HZ, you could have a light flasher you could
hear.  Since the wave form was abrupt, you could listen to your
light flasher tick at even lower frequencies.

	If my 69-year-old memory serves me, some of the
electronic organs of by-gone days had a master oscillator octave
around High C and then got their base and mid-range notes by a
series of NE2 lamps wired as relaxation oscillators which
phase-locked on to the note above so only the master octave had
to be tuned and all the rest acted as binary dividers before
integrated circuits came along.

	I once tried to improve the squelch circuit on a tunable
VHF radio in 1968 by putting a NE2 lamp in the squelch circuit.
It worked beautifully if the under side of the chassis was
exposed to light but light helps ionize the neon and changes the
breakdown voltage so the ne2's trigger point kept changing after
I closed up the case.

	Martin
--=20
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