On Sat, 19 Apr 2014 22:03:33 +0100, Tim Streater wrote:

In article , Uncle Peter wrote:

On Sat, 19 Apr 2014 21:11:26 +0100, Vir Campestris
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

I'm not that old.

"Current" ones (ie solid state) lock to the flyback pulses in the
transmission, and don't take any notice of mains.

I'm 38, and I had a TV as a kid that had vertical and horizontal hold. Is
this anything to do with it?

Don't think so. I think that was just a manifestation of the fact that
component drift with temperature was worse back then. More recent CRT
tellies didn't have them - or they could lock on better.

I didn't have to adjust it with temperature. Once adjusted, it was fine when cold and warm. It would drift out after a few months.

--
Amanpreet was overheard at the hospital angrily say, "My wife just delivered twins!!!"
A passerby said, "So? You should be happy about that. Why are you so angry?"
"I want to know who the son of a bitch is that's the father of the second kid!"

On Sat, 19 Apr 2014 22:59:15 +0100, John Williamson wrote:

On 19/04/2014 22:03, Tim Streater wrote:
In article , Uncle Peter wrote:

On Sat, 19 Apr 2014 21:11:26 +0100, Vir Campestris
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

I'm not that old.

"Current" ones (ie solid state) lock to the flyback pulses in the
transmission, and don't take any notice of mains.

I'm 38, and I had a TV as a kid that had vertical and horizontal
hold. Is
this anything to do with it?

Don't think so. I think that was just a manifestation of the fact that
component drift with temperature was worse back then. More recent CRT
tellies didn't have them - or they could lock on better.

The latter. That and better temperature control inside the box due to
using solid state components instead of valves.

I wasn't referring to a valve telly.

--
People who don't like their beliefs being laughed at shouldn't have such funny beliefs

On Sat, 19 Apr 2014 22:57:50 +0100, John Williamson wrote:

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio and
the receiver locked its internal signals to the broadcast reference.

I see. So the locking in the studio was so the cameras didn't show
flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the incoming
AC, the flicker would have been exactly the same.

Not if the DC was smoothed well.

--
User has insufficient intelligence to complete this task, please insert a new user.

On 19/04/2014 23:01, Uncle Peter wrote:
On Sat, 19 Apr 2014 22:57:50 +0100, John Williamson
wrote:

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio and
the receiver locked its internal signals to the broadcast reference.

I see. So the locking in the studio was so the cameras didn't show
flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the incoming
AC, the flicker would have been exactly the same.

Not if the DC was smoothed well.

Do the sums. To adequately smooth the many kilowatts of lighting used in
the average studio in those days would take Farads of capacitance and
many Henrys of inductance. A single lamp could well be using about 5
kilowatts, and up to a dozen were in use for most shots.

But it wasn't a problem, and the lack of use for the studio in question
probably had more to do with the quality of the 525 line cameras than
the lighting flicker.

It was also, IIRC, better to convert from 625 lines PAL to 525 line NTSC
than the other way round.

--
Tciao for Now!

John.

On Sat, 19 Apr 2014 18:06:35 +0000 (UTC),
(Andrew Gabriel) wrote:

In article ,
Davey writes:
On Sat, 19 Apr 2014 13:26:31 +0100
"Dave Plowman (News)" wrote:

In article ,
charles wrote:
So why don't they flicker when the studio is running at 625/50 -
since it's not locked to the mains frequency? The eye would see a
flicker at much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than
0.1Hz?

It's one of these things which seem to vary from person to person.
Many complain about flicker from some 50 Hz fluorescent lights saying
it gives them a headache. I can't say I've ever noticed it.


My wife complained about them even in the US, whereas they have never
bothered me anywhere. Except in China, where the hotel lights, all of
them, flickered at about 1.5 Hz.

No one can see 100Hz flicker - the limit is below 75Hz.

IME, that seems to be true. However, when I was testing refresh rates
with a 19 inch CRT monitor, I could just about discern the flicker at
75Hz when observing from the near periphery field of vision but it
wasn't troublesome otherwise.

I think I chose 85Hz (when the choices included up to 120Hz for the
1280 by 960 screen resolution I was using) simply to save unnecessary
stress on the LOPT circuitry.

60Hz refresh rate was too ghastly to bear on a CRT but perfectly fine
on an LCD based display panel (as would be true for 17 and 25Hz
refresh rates if we leave aside the need to satisfy moving image
requirements).

Animals with smaller brains can see higher frequencies,
and flies can see 1000Hz flicker.

I'm our household pets appreciate the change from CRT to LCD displays
even more than we do (especially the flies). :-)


With discharge tubes, a problem can be that they are partially
rectifying, resulting in 50Hz (or 60Hz) flicker, and most people
can see that. High intensity discharge lighting in shops was
often run on DC, to prevent this (prior to electronic ballasts).

Except for the use of DC in the case of high intensity discharge
lamps (sans a phosphor coating), I'd already pointed this out in
yesterday's afternoon posting.

There's a DC switching unit which alternates the DC flow every
switch-on, so you still get most of the expected lamp life.
This doesn't work with fluorescent tubes, because the mercury
tends to migrate to one end after some hours, leaving the other
end of the tube glowing only a very dim pink (argon gas).

In which case, the DC ballast aught to introduce a swift reversal
every couple of hours runtime regardless if it's only a matter of a
few hours (depends on what defines 'a few hours' though).
--
Regards, J B Good

On Sat, 19 Apr 2014 21:16:30 +0100, John Rumm
wrote:

On 19/04/2014 13:26, Dave Plowman (News) wrote:
In article ,
charles wrote:
So why don't they flicker when the studio is running at 625/50 - since
it's not locked to the mains frequency? The eye would see a flicker at
much lower speeds than 10 a second.

I'm not a physician. Could the brain sense flicker at less than 0.1Hz?

It's one of these things which seem to vary from person to person. Many
complain about flicker from some 50 Hz fluorescent lights saying it gives
them a headache. I can't say I've ever noticed it.

Much depends on the circumstance I find. 50Hz lights don't seem to
bother me particularly, but CRT flicker at anything less than about 82Hz
really bugs me. (as do modern electronic cats eyes, and some brake
lights, and many LED displays etc).

Don't overlook the fact that the flicker rate of a lamp will be twice
the mains frequency so all those 50Hz lights are actually flickering
at 100Hz. Fluorescent lamps can introduce a 50Hz flicker component
when the cathodes start wearing out. AFAICR from my "Lamps and
Lighting", the imbalance only needs to a mere 3% for it to become
observable by most people.

Multiplexed displays (whether gas discharge or LED based) tend to
have very low refresh rates in relation to hiding the effect that's
magnified by the very low duty cycle of each digit which, on an eight
digit display will be less than 12.5% for each of the 8 digits.
digital oven clocks are a prime example of this deficiency.

As for LED rear brake lights and electronic cats eyes, the problem is
also exacerbated by very low duty cycles and them mainly being
observed in the near peripheral vision in very dark conditions.

Wobble of the image on the retina can produce a confusing mess of
'dots' instead of a smear if the refresh frequency is too low.
Provided the refresh rate is high enough, the resulting series of dots
should produce a 'join the dots' type of effect which is a far less
disconcerting facsimile of a smear we'd happily accept with continuous
illumination.

I'd say you're not alone in observing the worst evils of such
illumination.
--
Regards, J B Good

On Sat, 19 Apr 2014 21:43:39 +0100, "Uncle Peter" wrote:

On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio and
the receiver locked its internal signals to the broadcast reference.

I see. So the locking in the studio was so the cameras didn't show flicker on lighting? Or couldn't they just use DC lighting?

You're following a red herring with that line of thought. The reason
for locking to a wandering 50 or 60 Hz grid supply reference was to
stop the hum bars moving which rendered them invisible unless you
watched the TV screen at the end of the program day to detect the
vertical change of shading in the mid grey tone of the raster scan.

If the TV broadcasters hadn't locked the camera scan rates to the
mains frequency, the resulting moving hum bars would have detracted
noticably from the picture content.

By the time colour transmissions were introduced the LOPT supply
smoothing had significantly improved so that the moving hum bars could
only be observed at the end of the programming day, the change in
level due to less than perfect smoothing being too slight to be
observable during reception of program content.

Colour broadcasting required the line and vertical scan frequencies
to be precisely locked to the colour burst reference so could no
longer take advantage of the masking effect of 'locked hum bars'.

The TV set manufacturers were effectively forced to upgrade the
smoothing performance in the power supplies as a direct result (it was
not merely coincidence that the supplies were much better smoothed
with colour TV sets).
--
Regards, J B Good

On Sat, 19 Apr 2014 23:18:20 +0100, John Williamson wrote:

On 19/04/2014 23:01, Uncle Peter wrote:
On Sat, 19 Apr 2014 22:57:50 +0100, John Williamson
wrote:

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio and
the receiver locked its internal signals to the broadcast reference.

I see. So the locking in the studio was so the cameras didn't show
flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the incoming
AC, the flicker would have been exactly the same.

Not if the DC was smoothed well.

Do the sums. To adequately smooth the many kilowatts of lighting used in
the average studio in those days would take Farads of capacitance and
many Henrys of inductance. A single lamp could well be using about 5
kilowatts, and up to a dozen were in use for most shots.

So what? The percentage cost of the capacitance would be no different than doing it on a smaller scale.

But it wasn't a problem, and the lack of use for the studio in question
probably had more to do with the quality of the 525 line cameras than
the lighting flicker.

It was also, IIRC, better to convert from 625 lines PAL to 525 line NTSC
than the other way round.

This has been observed when we saw USA newsfeeds on the BBC.

--
Acupuncture is a jab well done.

On Sat, 19 Apr 2014 22:03:33 +0100, Tim Streater
wrote:

In article , Uncle Peter wrote:

On Sat, 19 Apr 2014 21:11:26 +0100, Vir Campestris
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

I'm not that old.

"Current" ones (ie solid state) lock to the flyback pulses in the
transmission, and don't take any notice of mains.

I'm 38, and I had a TV as a kid that had vertical and horizontal hold. Is
this anything to do with it?

Don't think so. I think that was just a manifestation of the fact that
component drift with temperature was worse back then. More recent CRT
tellies didn't have them - or they could lock on better.

No TV sets ever used the mains for sychronisation purposes. A TV set
was designed to lock onto the sync pulses in the over the air
broadcast signal. Since the cameras were locked to the mains frequency
in pre-colour systems, the TV set would end up locked to the mains
frequency automatically.

As regards the absence of front panel horizontal and vertical hold
adjustment controls in modern sets, this is largely down to modern
(only 2 decades or so old) digital sync extraction techniques and
(possibly) digital control of analogue components in the final line
and vertical scan circuitry. These controls would still exist but only
as internal 'trimmer' controls on the circuit board for factory
alignment and maintenance adjustments to counter drift in component
values with aging.
--
Regards, J B Good

In article ,
John Williamson wrote:
On 19/04/2014 23:01, Uncle Peter wrote:
On Sat, 19 Apr 2014 22:57:50 +0100, John Williamson
wrote:

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio and
the receiver locked its internal signals to the broadcast reference.

I see. So the locking in the studio was so the cameras didn't show
flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the incoming
AC, the flicker would have been exactly the same.

Not if the DC was smoothed well.

Do the sums. To adequately smooth the many kilowatts of lighting used in
the average studio in those days would take Farads of capacitance and
many Henrys of inductance. A single lamp could well be using about 5
kilowatts, and up to a dozen were in use for most shots.

But it wasn't a problem, and the lack of use for the studio in question
probably had more to do with the quality of the 525 line cameras than
the lighting flicker.

The same cameras were used for both 625/50 and 525/60.

It was also, IIRC, better to convert from 625 lines PAL to 525 line NTSC
than the other way round.

On the basis that there was more information in the 625/50 signal? But
remember that the full picture electronic standards converter didn't appear
on the scene until well after colour had started in the UK. The Mexico
Olympics (1968) was its first outing and that was only in the 525 625
mode.

--
From KT24

Using a RISC OS computer running v5.18

In article , Uncle Peter wrote:
On Sat, 19 Apr 2014 23:18:20 +0100, John Williamson
wrote:

On 19/04/2014 23:01, Uncle Peter wrote:
On Sat, 19 Apr 2014 22:57:50 +0100, John Williamson
wrote:

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio
and the receiver locked its internal signals to the broadcast
reference.

I see. So the locking in the studio was so the cameras didn't show
flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the
incoming AC, the flicker would have been exactly the same.

Not if the DC was smoothed well.

Do the sums. To adequately smooth the many kilowatts of lighting used
in the average studio in those days would take Farads of capacitance
and many Henrys of inductance. A single lamp could well be using about
5 kilowatts, and up to a dozen were in use for most shots.

So what? The percentage cost of the capacitance would be no different
than doing it on a smaller scale.

TC Studio 1 had an installed lighting load of around a quarter of a
megawatt.

But it wasn't a problem, and the lack of use for the studio in question
probably had more to do with the quality of the 525 line cameras than
the lighting flicker.

It was also, IIRC, better to convert from 625 lines PAL to 525 line
NTSC than the other way round.

This has been observed when we saw USA newsfeeds on the BBC.

You weren't seeing degradation introduced by standards conversion, you were
seeing that the incoming pictures weren't very good.

--
From KT24

Using a RISC OS computer running v5.18

In article ,
Uncle Peter wrote:
Do the sums. To adequately smooth the many kilowatts of lighting used in
the average studio in those days would take Farads of capacitance and
many Henrys of inductance. A single lamp could well be using about 5
kilowatts, and up to a dozen were in use for most shots.

So what? The percentage cost of the capacitance would be no different
than doing it on a smaller scale.

There's also the problem of being able to control the level of the lamps.

--
*I don't suffer from insanity, I enjoy every minute of it *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ,
charles wrote:
The same cameras were used for both 625/50 and 525/60.


I'll bet line up took ages when that switch was thrown. ;-)

--
*Eagles may soar, but weasels don't get sucked into jet engines *

Dave Plowman London SW
To e-mail, change noise into sound.

I see. So the locking in the studio was so the cameras didn't show flicker on
lighting? Or couldn't they just use DC lighting?

You're following a red herring with that line of thought. The reason
for locking to a wandering 50 or 60 Hz grid supply reference was to
stop the hum bars moving which rendered them invisible unless you
watched the TV screen at the end of the program day to detect the
vertical change of shading in the mid grey tone of the raster scan.

If the TV broadcasters hadn't locked the camera scan rates to the
mains frequency, the resulting moving hum bars would have detracted
noticably from the picture content.

By the time colour transmissions were introduced the LOPT supply
smoothing had significantly improved so that the moving hum bars could
only be observed at the end of the programming day, the change in
level due to less than perfect smoothing being too slight to be
observable during reception of program content.

LOPT supply smoothing?. What do you mean by that Johny?...


Colour broadcasting required the line and vertical scan frequencies
to be precisely locked to the colour burst reference so could no
longer take advantage of the masking effect of 'locked hum bars'.

The TV set manufacturers were effectively forced to upgrade the
smoothing performance in the power supplies as a direct result (it was
not merely coincidence that the supplies were much better smoothed
with colour TV sets).

--
Tony Sayer

On Sun, 20 Apr 2014 13:15:26 +0100, tony sayer
wrote:


I see. So the locking in the studio was so the cameras didn't show flicker on
lighting? Or couldn't they just use DC lighting?

You're following a red herring with that line of thought. The reason
for locking to a wandering 50 or 60 Hz grid supply reference was to
stop the hum bars moving which rendered them invisible unless you
watched the TV screen at the end of the program day to detect the
vertical change of shading in the mid grey tone of the raster scan.

If the TV broadcasters hadn't locked the camera scan rates to the
mains frequency, the resulting moving hum bars would have detracted
noticably from the picture content.

By the time colour transmissions were introduced the LOPT supply
smoothing had significantly improved so that the moving hum bars could
only be observed at the end of the programming day, the change in
level due to less than perfect smoothing being too slight to be
observable during reception of program content.

LOPT supply smoothing?. What do you mean by that Johny?...

Line OutPut Transformer - used to generate the 25 or so KV from an
overwind on said transformer using the horizontal flyback pulses to
feed the eht rectifier valve or HV silicon diode / diode string (half
wave rectification using the picture tube itself as the EHT smoothing
capacitor).

If the LOPT driver circuit is powered from an insufficiently smoothed
supply, the EHT will have this ripple superimposed upon it and show up
as a variation in picture brightness ('Hum Bars').

Of course, you will see similar effects if the supply to the video
amplifier channels is similarly afflicted. Indeed, it's likely to be
the sum effect of these two sources of ripple interference by a badly
filtered common source supply rail.

The early colour TV sets in the UK were hybrid valve/transistor
designs where the penultimate LOPT driver valve was the last to be
usurped by a very fast high voltage power transistor (the final
irreplacable valve being the picture tube itself).

The low voltage psu for the transistor stages could easily be
designed to eliminate mains ripple, leaving just the LOPT valve driver
HT perhaps still relying on an older style less than perfect filtered
supply.

I suppose the later hybrid designs could have made good use of high
voltage power transistor to regulate the 300 odd volt HT supply and
eliminate even this residual source of 'hum' (or perhaps, more likely
now I think about it, an SMPSU was used where the only high voltage
fast semiconductors required would be the fast switching rectifier
diodes).
--
Regards, J B Good

On Sun, 20 Apr 2014 11:06:24 +0100, Dave Plowman (News) wrote:

In article ,
Uncle Peter wrote:
Do the sums. To adequately smooth the many kilowatts of lighting used in
the average studio in those days would take Farads of capacitance and
many Henrys of inductance. A single lamp could well be using about 5
kilowatts, and up to a dozen were in use for most shots.

So what? The percentage cost of the capacitance would be no different
than doing it on a smaller scale.

There's also the problem of being able to control the level of the lamps.

Why would that be a problem?

--
Helpdesk: Click on the 'my computer' icon on the left of the screen.
Customer: Your left or my left?

On Sun, 20 Apr 2014 08:35:31 +0100, charles wrote:

In article , Uncle Peter wrote:
On Sat, 19 Apr 2014 23:18:20 +0100, John Williamson
wrote:

On 19/04/2014 23:01, Uncle Peter wrote:
On Sat, 19 Apr 2014 22:57:50 +0100, John Williamson
wrote:

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the studio
and the receiver locked its internal signals to the broadcast
reference.

I see. So the locking in the studio was so the cameras didn't show
flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the
incoming AC, the flicker would have been exactly the same.

Not if the DC was smoothed well.

Do the sums. To adequately smooth the many kilowatts of lighting used
in the average studio in those days would take Farads of capacitance
and many Henrys of inductance. A single lamp could well be using about
5 kilowatts, and up to a dozen were in use for most shots.

So what? The percentage cost of the capacitance would be no different
than doing it on a smaller scale.

TC Studio 1 had an installed lighting load of around a quarter of a
megawatt.

And the percentage cost of smoothing the DC for it would be the same as if it was a quarter of a kilowatt.

But it wasn't a problem, and the lack of use for the studio in question
probably had more to do with the quality of the 525 line cameras than
the lighting flicker.

It was also, IIRC, better to convert from 625 lines PAL to 525 line
NTSC than the other way round.

This has been observed when we saw USA newsfeeds on the BBC.

You weren't seeing degradation introduced by standards conversion, you were
seeing that the incoming pictures weren't very good.

They looked a lot worse than 100 missing lines.

--
"You might show me a little more respect" complained the coed as she and her date were driving back from "Lover's Lookout".
"Yeah?" asked the smirking boy, "Like by doing what?"
"Well, for starters, not flying my panty hose from your radio aerial."

On Sun, 20 Apr 2014 00:17:18 +0100, Johny B Good wrote:

On Sat, 19 Apr 2014 22:03:33 +0100, Tim Streater
wrote:

In article , Uncle Peter wrote:

On Sat, 19 Apr 2014 21:11:26 +0100, Vir Campestris
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide to
frequency?

I'm not that old.

"Current" ones (ie solid state) lock to the flyback pulses in the
transmission, and don't take any notice of mains.

I'm 38, and I had a TV as a kid that had vertical and horizontal hold. Is
this anything to do with it?

Don't think so. I think that was just a manifestation of the fact that
component drift with temperature was worse back then. More recent CRT
tellies didn't have them - or they could lock on better.

No TV sets ever used the mains for sychronisation purposes. A TV set
was designed to lock onto the sync pulses in the over the air
broadcast signal. Since the cameras were locked to the mains frequency
in pre-colour systems, the TV set would end up locked to the mains
frequency automatically.

As regards the absence of front panel horizontal and vertical hold
adjustment controls in modern sets, this is largely down to modern
(only 2 decades or so old) digital sync extraction techniques and
(possibly) digital control of analogue components in the final line
and vertical scan circuitry. These controls would still exist but only
as internal 'trimmer' controls on the circuit board for factory
alignment and maintenance adjustments to counter drift in component
values with aging.

If TVs have always locked onto the sync pulses, what on earth did the hold controls do?

--
Britney Spears is pregnant. She plans to breast feed.
In other words, the child will have an abundant supply of artificial milk.

In article , Uncle Peter wrote:
On Sun, 20 Apr 2014 08:35:31 +0100, charles
wrote:

In article , Uncle Peter wrote:
On Sat, 19 Apr 2014 23:18:20 +0100, John Williamson
wrote:

On 19/04/2014 23:01, Uncle Peter wrote:
On Sat, 19 Apr 2014 22:57:50 +0100, John Williamson
wrote:

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the
studio and the receiver locked its internal signals to the
broadcast reference.

I see. So the locking in the studio was so the cameras didn't
show flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the
incoming AC, the flicker would have been exactly the same.

Not if the DC was smoothed well.

Do the sums. To adequately smooth the many kilowatts of lighting
used in the average studio in those days would take Farads of
capacitance and many Henrys of inductance. A single lamp could well
be using about 5 kilowatts, and up to a dozen were in use for most
shots.

So what? The percentage cost of the capacitance would be no different
than doing it on a smaller scale.

TC Studio 1 had an installed lighting load of around a quarter of a
megawatt.

And the percentage cost of smoothing the DC for it would be the same as
if it was a quarter of a kilowatt.

Agreed, but it would be a very large sum

But it wasn't a problem, and the lack of use for the studio in
question probably had more to do with the quality of the 525 line
cameras than the lighting flicker.

It was also, IIRC, better to convert from 625 lines PAL to 525 line
NTSC than the other way round.

This has been observed when we saw USA newsfeeds on the BBC.

You weren't seeing degradation introduced by standards conversion, you
were seeing that the incoming pictures weren't very good.

They looked a lot worse than 100 missing lines.

They looked bad when we saw them in the original standard. Nothing to do
with missing lines.

--
From KT24

Using a RISC OS computer running v5.18

In article , Uncle Peter wrote:
On Sun, 20 Apr 2014 00:17:18 +0100, Johny B Good
wrote:

On Sat, 19 Apr 2014 22:03:33 +0100, Tim Streater
wrote:

In article , Uncle Peter
wrote:

On Sat, 19 Apr 2014 21:11:26 +0100, Vir Campestris
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:
So how did TVs work properly when they used the mains as a guide
to frequency?

I'm not that old.

"Current" ones (ie solid state) lock to the flyback pulses in the
transmission, and don't take any notice of mains.

I'm 38, and I had a TV as a kid that had vertical and horizontal
hold. Is this anything to do with it?

Don't think so. I think that was just a manifestation of the fact that
component drift with temperature was worse back then. More recent CRT
tellies didn't have them - or they could lock on better.

No TV sets ever used the mains for sychronisation purposes. A TV set
was designed to lock onto the sync pulses in the over the air broadcast
signal. Since the cameras were locked to the mains frequency in
pre-colour systems, the TV set would end up locked to the mains
frequency automatically.

As regards the absence of front panel horizontal and vertical hold
adjustment controls in modern sets, this is largely down to modern
(only 2 decades or so old) digital sync extraction techniques and
(possibly) digital control of analogue components in the final line and
vertical scan circuitry. These controls would still exist but only as
internal 'trimmer' controls on the circuit board for factory alignment
and maintenance adjustments to counter drift in component values with
aging.

If TVs have always locked onto the sync pulses, what on earth did the
hold controls do?

They were in the circuitry which separted out the line & field syncs from
the received signal. Things drifted.

--
From KT24

Using a RISC OS computer running v5.18

On Sun, 20 Apr 2014 22:51:01 +0100, "Uncle Peter" wrote:



If TVs have always locked onto the sync pulses, what on earth did the hold controls do?

Adjust the free running oscillators involved so that they were within
locking range of the sync pulses. They were deemed to require operator
intervention in the early days to compensate for temperature drift and
aging effects (also, it meant that they could be fine trimmed to
improve lock on weak / noisy signals).

Modern TV sets from about 2 decades ago lost these 'operator
controls' due to improvements in sync circuit designs rendering such
adjustments redundent. CRT TVs and computer monitors retained them
purely as an on the board alignment pot or two to allow a service
engineer to compensate for aging effects.

Such analogue adjustments no longer exist with flat panel displays
simply because the pixel addressing is entirely digital and modern
synthesised TV tuners can reliably extract the sync pulses on analogue
signals (of academic interest only for UK broadcast TV now that
analogue broadcasting has ended - but still useful for some amateur
fast scan TV reception or foreign DX analogue TV activities).

DVB-T encodes the picture content such that any such synchronisation
information is just part of the video data stream. Ignoring the
analogue tuner feature which still exists in all but perhaps the
latest TV sets, a modern flat panel TV is just a dedicated computer
with an embedded OS that processes the media streams in pretty much
the same way as a PC would when playing an MPG video file (except for
the inclusion of the FEC overhead in the broadcast stream).
--
Regards, J B Good

LOPT supply smoothing?. What do you mean by that Johny?...

Line OutPut Transformer - used to generate the 25 or so KV from an
overwind on said transformer using the horizontal flyback pulses to
feed the eht rectifier valve or HV silicon diode / diode string (half
wave rectification using the picture tube itself as the EHT smoothing
capacitor).

If the LOPT driver circuit is powered from an insufficiently smoothed
supply, the EHT will have this ripple superimposed upon it and show up
as a variation in picture brightness ('Hum Bars').


Yes know what the olde LOPT'y did but odd that smoothing ripple as you
describe. Can't remember ever seeing that but that might be the sets I
worked on most were Phillips Mono and G8 and G11 colour chassis so I
suppose they must have been another make perhaps?...

Of course, you will see similar effects if the supply to the video
amplifier channels is similarly afflicted. Indeed, it's likely to be
the sum effect of these two sources of ripple interference by a badly
filtered common source supply rail.

Never recall seeing that either but what we did see a lot was a heater
cathode leak on the frame output stage of several TV's one Phillips
chassis was very good at that so they put a fusible resistor or two in
the cathode line to earth and they often came off with the resultant
over current then the bypass cap was left to take the load which it did
till it couldn't take it no more, it then spew its guts over the PCB far
and wide and if you didn't clean that off, all of it, then other
interesting things happened;!...


The early colour TV sets in the UK were hybrid valve/transistor
designs where the penultimate LOPT driver valve was the last to be
usurped by a very fast high voltage power transistor (the final
irreplacable valve being the picture tube itself).

Never did see many of those, Philips G6 a few off and the K7 chassis a
noted excellent performer with superb sound..

After that it was BU 205's IIRC?..


The low voltage psu for the transistor stages could easily be
designed to eliminate mains ripple, leaving just the LOPT valve driver
HT perhaps still relying on an older style less than perfect filtered
supply.

I suppose the later hybrid designs could have made good use of high
voltage power transistor to regulate the 300 odd volt HT supply and
eliminate even this residual source of 'hum' (or perhaps, more likely
now I think about it, an SMPSU was used where the only high voltage
fast semiconductors required would be the fast switching rectifier
diodes).


In the G8 it was a thyristor and can't remember now what it was in the
G11 all getting to be a long timer ago;!!..

--
Tony Sayer

On Sun, 20 Apr 2014 23:05:24 +0100, charles wrote:

In article , Uncle Peter wrote:
On Sun, 20 Apr 2014 08:35:31 +0100, charles
wrote:

In article , Uncle Peter wrote:
On Sat, 19 Apr 2014 23:18:20 +0100, John Williamson
wrote:

On 19/04/2014 23:01, Uncle Peter wrote:
On Sat, 19 Apr 2014 22:57:50 +0100, John Williamson
wrote:

On 19/04/2014 21:43, Uncle Peter wrote:
On Sat, 19 Apr 2014 20:58:40 +0100, John Williamson
wrote:

On 19/04/2014 20:48, Uncle Peter wrote:

The same way as they did after they got rid of the mains lock.

The video signals were locked to the mains reference in the
studio and the receiver locked its internal signals to the
broadcast reference.

I see. So the locking in the studio was so the cameras didn't
show flicker on lighting? Or couldn't they just use DC lighting?

As the DC would have been obtained by using rectifiers on the
incoming AC, the flicker would have been exactly the same.

Not if the DC was smoothed well.

Do the sums. To adequately smooth the many kilowatts of lighting
used in the average studio in those days would take Farads of
capacitance and many Henrys of inductance. A single lamp could well
be using about 5 kilowatts, and up to a dozen were in use for most
shots.

So what? The percentage cost of the capacitance would be no different
than doing it on a smaller scale.

TC Studio 1 had an installed lighting load of around a quarter of a
megawatt.

And the percentage cost of smoothing the DC for it would be the same as
if it was a quarter of a kilowatt.

Agreed, but it would be a very large sum

If something costs you £1,000 to buy, and you have to spend an extra tenner to make it work better, you wouldn't say that was much.
Equally, if something costs you £100,000,000 to buy and you have to spend an extra million, you also wouldn't say that was much. They are both 1%.

But it wasn't a problem, and the lack of use for the studio in
question probably had more to do with the quality of the 525 line
cameras than the lighting flicker.

It was also, IIRC, better to convert from 625 lines PAL to 525 line
NTSC than the other way round.

This has been observed when we saw USA newsfeeds on the BBC.

You weren't seeing degradation introduced by standards conversion, you
were seeing that the incoming pictures weren't very good.

They looked a lot worse than 100 missing lines.

They looked bad when we saw them in the original standard. Nothing to do
with missing lines.

Something other than 100 lines less caused NTSC to suck?

--
After pleading no contest to burglarizing Britney Spears's home, four men received three years of probation.
All they had to do was sign an agreement not to reveal what they stole from the house or how many batteries it took.

In article ,
Uncle Peter wrote:
On Sun, 20 Apr 2014 23:05:24 +0100, charles wrote:



[Snip]

They looked bad when we saw them in the original standard. Nothing to
do with missing lines.

Something other than 100 lines less caused NTSC to suck?

according to some NTSC stood for Never Twice the Same Color.

When there was a US director for the UK content of an American program, he
didn't like the accurate flesh tones that came out of our cameras: "They've
paid for color, give them color!"

etc

--
From KT24

Using a RISC OS computer running v5.18

In article ,
Uncle Peter wrote:
There's also the problem of being able to control the level of the
lamps.

Why would that be a problem?

How would you control the level of DC lamps in the '60s?

--
*There's no place like www.home.com *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...

In article ,
Uncle Peter wrote:
There's also the problem of being able to control the level of the
lamps.

Why would that be a problem?

How would you control the level of DC lamps in the '60s?


Salt bath was popular in theatres in the late 50's if a rheostat worked out
too large

Andrew

In article ,
Andrew Mawson wrote:
"Dave Plowman (News)" wrote in message
...

In article ,
Uncle Peter wrote:
There's also the problem of being able to control the level of the
lamps.

Why would that be a problem?

How would you control the level of DC lamps in the '60s?


Salt bath was popular in theatres in the late 50's if a rheostat worked
out too large

Must have been interesting controlling the levels from the lighting
control room? A series of taps rather than faders?

--
*I didn't drive my husband crazy -- I flew him there -- it was faster

Dave Plowman London SW
To e-mail, change noise into sound.

On Mon, 21 Apr 2014 12:18:09 +0100
charles wrote:

Something other than 100 lines less caused NTSC to suck?

according to some NTSC stood for Never Twice the Same Color.

When I first moved to the US in the 1970s/80s, that was pretty accurate,
there were some really lurid images to be seen, in stark contrast to
what I had left behind here.

--
Davey.

On Mon, 21 Apr 2014 13:12:04 +0100, Dave Plowman (News) wrote:

In article ,
Uncle Peter wrote:
There's also the problem of being able to control the level of the
lamps.

Why would that be a problem?

How would you control the level of DC lamps in the '60s?

Did they not have chopper circuits then?

--
On a Continental Flight with a very "senior" flight attendant crew, the pilot said,
"Ladies and gentlemen, we've reached cruising altitude and will be turning down the cabin lights.
This is for your comfort, and to enhance the appearance of your flight attendants."

On Mon, 21 Apr 2014 12:18:09 +0100, charles wrote:

In article ,
Uncle Peter wrote:
On Sun, 20 Apr 2014 23:05:24 +0100, charles wrote:



[Snip]

They looked bad when we saw them in the original standard. Nothing to
do with missing lines.

Something other than 100 lines less caused NTSC to suck?

according to some NTSC stood for Never Twice the Same Color.

When there was a US director for the UK content of an American program, he
didn't like the accurate flesh tones that came out of our cameras: "They've
paid for color, give them color!"

etc

Ah yes I'd forgotten their colour encoding was dodgy. It's inside one of the other signals, or seperate and not synced right, or something. The opposite of what PAL does.

--
"Flashlights are tubular metal containers kept in a flight bag for the purpose of storing dead batteries."

On 21/04/2014 19:28, Uncle Peter wrote:
On Mon, 21 Apr 2014 12:18:09 +0100, charles
wrote:

In article ,
Uncle Peter wrote:
On Sun, 20 Apr 2014 23:05:24 +0100, charles
wrote:



[Snip]

They looked bad when we saw them in the original standard. Nothing to
do with missing lines.

Something other than 100 lines less caused NTSC to suck?

according to some NTSC stood for Never Twice the Same Color.

When there was a US director for the UK content of an American
program, he
didn't like the accurate flesh tones that came out of our cameras:
"They've
paid for color, give them color!"

etc

Ah yes I'd forgotten their colour encoding was dodgy. It's inside one
of the other signals, or seperate and not synced right, or something.
The opposite of what PAL does.

In a few seconds, you could use a search engine to find out the
differences between NTSC and PAL.

--
Tciao for Now!

John.

On Mon, 21 Apr 2014 20:27:16 +0100, John Williamson wrote:

On 21/04/2014 19:28, Uncle Peter wrote:
On Mon, 21 Apr 2014 12:18:09 +0100, charles
wrote:

In article ,
Uncle Peter wrote:
On Sun, 20 Apr 2014 23:05:24 +0100, charles
wrote:



[Snip]

They looked bad when we saw them in the original standard. Nothing to
do with missing lines.

Something other than 100 lines less caused NTSC to suck?

according to some NTSC stood for Never Twice the Same Color.

When there was a US director for the UK content of an American
program, he
didn't like the accurate flesh tones that came out of our cameras:
"They've
paid for color, give them color!"

etc

Ah yes I'd forgotten their colour encoding was dodgy. It's inside one
of the other signals, or seperate and not synced right, or something.
The opposite of what PAL does.

In a few seconds, you could use a search engine to find out the
differences between NTSC and PAL.

You must read fast.

--
If the Pope goes #2, does that make it "Holy ****"?

When there was a US director for the UK content of an American program, he
didn't like the accurate flesh tones that came out of our cameras: "They've
paid for color, give them color!"

etc

Ah yes I'd forgotten their colour encoding was dodgy. It's inside one of the
other signals, or seperate and not synced right, or something. The opposite
of what PAL does.

Both NTSC and PAL encode the colour some MHz away from the main
carrier, IIRC. The difficulty is to define what the phase of the colour
is, so with NTSC you have to have the user do it with a tint control
knob. PAL neatly overcomes that by inverting the sense of the phase for
alternate lines, hence what PAL stands for. I think PAL also uses a bit
more bandwidth so with NTSC there's more chance of getting the edge of
the colour signal mixed up with the b/w part of the picture, noticeable
if there is a lot of detail.


Down to how good the filtering was in the receiver some were good, some
some weren't too bright;!..

IME it also mixes with the sound carrier

Depending on how good that was too intercarrier sound did work well if
designed and adjusted right otherwise "intercarrier buzz"..


if you used a cheap telly in the US. But it seems that people don't
notice defects of that sort to the same extent that I do

Problem is a lot don't know any better;(..

- sound on
vision or the reverse, the colour turned up full,

Well we paid a lorra money for this 'ere telly so we want our moneys
worth;!..

horrible pin-cushion
or barrel distortion, etc.

Fortunately most of that is in the past now. They were showing the 1985
snooker world final yesterday, its amazing how crap the camera optics
must have been then - lots of flare and chromatic aberration that you
just don't get now.

I remember watching some pix from the Olympics must have been around
1972 or thereabouts on a Philips K7 TV, superb pix they were too colour
difference drive on the set always seem to have the edge over RGB...


--
Tony Sayer

On 21/04/2014 20:57, Uncle Peter wrote:
On Mon, 21 Apr 2014 20:27:16 +0100, John Williamson
wrote:

On 21/04/2014 19:28, Uncle Peter wrote:
Ah yes I'd forgotten their colour encoding was dodgy. It's inside one
of the other signals, or seperate and not synced right, or something.
The opposite of what PAL does.

In a few seconds, you could use a search engine to find out the
differences between NTSC and PAL.

You must read fast.

Getting the information onto the screen takes seconds. How long it takes
you to understand it depends on your comprehension skills. I learnt it a
few decades ago, when I was lining up analogue cameras and TV sets.

--
Tciao for Now!

John.

In article ,
Dave Plowman (News) wrote:
In article ,
Andrew Mawson wrote:
"Dave Plowman (News)" wrote in message
...

In article ,
Uncle Peter wrote:
There's also the problem of being able to control the level of the
lamps.

Why would that be a problem?

How would you control the level of DC lamps in the '60s?


Salt bath was popular in theatres in the late 50's if a rheostat worked
out too large

Must have been interesting controlling the levels from the lighting
control room? A series of taps rather than faders?

no, you had chains dangling in the salt bath and pulled them in or out
depending on the lightiing level. Usually done with a geared machanism
rather than bare hands.

--
From KT24

Using a RISC OS computer running v5.18

On Mon, 21 Apr 2014 22:16:55 +0100, Tim Streater wrote:

In article , Uncle Peter wrote:

On Mon, 21 Apr 2014 12:18:09 +0100, charles
wrote:

In article ,
Uncle Peter wrote:
On Sun, 20 Apr 2014 23:05:24 +0100, charles
wrote:



[Snip]

They looked bad when we saw them in the original standard. Nothing to
do with missing lines.

Something other than 100 lines less caused NTSC to suck?

according to some NTSC stood for Never Twice the Same Color.

When there was a US director for the UK content of an American program, he
didn't like the accurate flesh tones that came out of our cameras: "They've
paid for color, give them color!"

etc

Ah yes I'd forgotten their colour encoding was dodgy. It's inside one of the
other signals, or seperate and not synced right, or something. The opposite
of what PAL does.

Both NTSC and PAL encode the colour some MHz away from the main
carrier, IIRC. The difficulty is to define what the phase of the colour
is, so with NTSC you have to have the user do it with a tint control
knob. PAL neatly overcomes that by inverting the sense of the phase for
alternate lines, hence what PAL stands for. I think PAL also uses a bit
more bandwidth so with NTSC there's more chance of getting the edge of
the colour signal mixed up with the b/w part of the picture, noticeable
if there is a lot of detail. IME it also mixes with the sound carrier
if you used a cheap telly in the US. But it seems that people don't
notice defects of that sort to the same extent that I do - sound on
vision or the reverse, the colour turned up full, horrible pin-cushion
or barrel distortion, etc.

Fortunately most of that is in the past now. They were showing the 1985
snooker world final yesterday, its amazing how crap the camera optics
must have been then - lots of flare and chromatic aberration that you
just don't get now.

I'm also very fussy. In fact I detest watching non-HD stuff! Especially if that broadcaster has paid for a narrower bandwidth and it's over-compressed.
I also hated using anything less than a 90Hz CRT monitor, yet colleagues couldn't detect the flicker at 60Hz!

--
Computers are like air conditioners: They stop working when you open Windows.

On Tue, 22 Apr 2014 08:44:10 +0100, John Williamson wrote:

On 21/04/2014 20:57, Uncle Peter wrote:
On Mon, 21 Apr 2014 20:27:16 +0100, John Williamson
wrote:

On 21/04/2014 19:28, Uncle Peter wrote:
Ah yes I'd forgotten their colour encoding was dodgy. It's inside one
of the other signals, or seperate and not synced right, or something.
The opposite of what PAL does.

In a few seconds, you could use a search engine to find out the
differences between NTSC and PAL.

You must read fast.

Getting the information onto the screen takes seconds. How long it takes
you to understand it depends on your comprehension skills. I learnt it a
few decades ago, when I was lining up analogue cameras and TV sets.

Certainly not in seconds. And you had more reason to need to learn it.

--
If a person with multiple personalities threatens suicide, is that person considered a hostage situation?

On Tue, 22 Apr 2014 08:53:08 +0100, charles wrote:

In article ,
Dave Plowman (News) wrote:
In article ,
Andrew Mawson wrote:
"Dave Plowman (News)" wrote in message
...

In article ,
Uncle Peter wrote:
There's also the problem of being able to control the level of the
lamps.

Why would that be a problem?

How would you control the level of DC lamps in the '60s?


Salt bath was popular in theatres in the late 50's if a rheostat worked
out too large

Must have been interesting controlling the levels from the lighting
control room? A series of taps rather than faders?

no, you had chains dangling in the salt bath and pulled them in or out
depending on the lightiing level. Usually done with a geared machanism
rather than bare hands.

Wimp!

--
A guy bought his wife a beautiful diamond ring for Christmas.
A friend of his said, "I thought she wanted one of those sporty 4-Wheel drive vehicles."
"She did," he replied. "But where in the hell was I gonna find a fake Jeep?"