In article , Dave Plowman (News)
scribeth thus
In article ,
David Looser wrote:
- the 500vA or so
transformer needed to isolate the chassis was an expensive component.


The standard all-valve "large screen" TV of the 50s/early 60s consumed
150W, of which half went into keeping the heaters alight. So a 250VA
transformer would have been plenty big enough.

Even so that was a very expensive component and the way TV design was
costed to the nearest fraction of a penny made it a no go!..


My first generation colour set was 500 watts. And due to the rectifier
loads a 1000 watt isolating transformer would have been more suited.

Must've been a G6 then?...
--
Tony Sayer

In article ,
tony sayer wrote:
The standard all-valve "large screen" TV of the 50s/early 60s consumed
150W, of which half went into keeping the heaters alight. So a 250VA
transformer would have been plenty big enough.

Even so that was a very expensive component and the way TV design was
costed to the nearest fraction of a penny made it a no go!..

Yup - they left out the black level clamp from most sets and the cost of
those components would have been less than a transformer.


My first generation colour set was 500 watts. And due to the rectifier
loads a 1000 watt isolating transformer would have been more suited.

Must've been a G6 then?...

Oh yes. ;-) Cracking set when it worked.

--
*Corduroy pillows are making headlines.

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

"tony sayer" wrote in message
...
In article , Dave Plowman (News)
scribeth thus
In article ,
David Looser wrote:
- the 500vA or so
transformer needed to isolate the chassis was an expensive component.


The standard all-valve "large screen" TV of the 50s/early 60s consumed
150W, of which half went into keeping the heaters alight. So a 250VA
transformer would have been plenty big enough.

Even so that was a very expensive component and the way TV design was
costed to the nearest fraction of a penny made it a no go!..

Indeed, and it also added significantly to the weight and bulk to the set.
In my "den" I have a Pye B16T (which has an isolating mains transformer) and
a transformerless Bush TV22 sitting next to each other. Both have the same
tube type (9" Mullard MW22-16) but the difference in the size and weight of
these two is considerable. It was the advent of the AC/DC TV which made TV
cheap enough for it to become a mass-market product.


David.

"Dave Plowman (News)" wrote in message
...
In article ,
tony sayer wrote:
The standard all-valve "large screen" TV of the 50s/early 60s consumed
150W, of which half went into keeping the heaters alight. So a 250VA
transformer would have been plenty big enough.

Even so that was a very expensive component and the way TV design was
costed to the nearest fraction of a penny made it a no go!..

Yup - they left out the black level clamp from most sets and the cost of
those components would have been less than a transformer.


It was worse than that. The great majority of those sets also used the
abomination known as "mean-level AGC" In which the control voltage for AGC
to the RF and IF amplifiers by obtained simply by low-pass filtering the
negative going video signal found at the grid of the sync separator. So the
gain was wound up on low key scenes, and wound down on high-key scenes.
After this there was little point in trying to keep the black level
constant.. There were a few manufacturers brave enough to put TVs with gated
AGC and DC coupled video onto the market, but the GBP demonstrated that it
wasn't prepared to pay even a small premium for such trivial points as a
correctly presented picture, or decent sound. What mattered was the size of
the picture and what the cabinet looked like.

David.

In article ,
David Looser wrote:
Yup - they left out the black level clamp from most sets and the cost
of those components would have been less than a transformer.


It was worse than that. The great majority of those sets also used the
abomination known as "mean-level AGC" In which the control voltage for
AGC to the RF and IF amplifiers by obtained simply by low-pass filtering
the negative going video signal found at the grid of the sync separator.
So the gain was wound up on low key scenes, and wound down on high-key
scenes. After this there was little point in trying to keep the black
level constant.. There were a few manufacturers brave enough to put TVs
with gated AGC and DC coupled video onto the market, but the GBP
demonstrated that it wasn't prepared to pay even a small premium for
such trivial points as a correctly presented picture, or decent sound.
What mattered was the size of the picture and what the cabinet looked
like.

Indeed. I remember seeing a demonstration where a telecine loop of several
frames of black was followed by several of 'white' and repeated. Most
domestic sets showed a near constant grey...

--
*Just remember...if the world didn't suck, we'd all fall off*

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