You've misunderstood the original quote, the TV isn't synced to the mains (as you say the TV is obviously synced to the received signal) - it's the transmitted signal that is 'synced' to the mains - it might not be directly, but it is synced to prevent moving hum bars on the receiver.

Although the hum bar problem disappeared many years ago!.

__________________
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You know what I mean. The vertical rate for black and white TV broadcasts was 60.0000Hz.

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Uncle $crooge

 

Read some interesting tv stuff here , i started serving my time in the tv trade in 1969 back then tv was mostly valve (tubes us ) in the workshop was still to be found a lot of vintage sets these where mono 405 line with fm video and am audio now it wasnt just as simple as switching on the set some of these monsters had as many as 15 user controls , now most of these early sets where synced of the mains power so when a set was switched on the brightness was turned fully low and the audio volume to mid , as the set heated up and audio was heard you would advance brightness to see a picture , now if your home was powered on a differant power station or phase then the picture would be out of sync vertically and horizontily so you would then adjust hor and ver controls to match the sync of the transmitter studio . Now sometimes at night owing to demand power stations would change taps in there substations or connect to another phase this would mean that your tv would go out of sync and need readjusted this is where the term " the sets on the blink come from "!

the modern sets employ sync from the studio via sync separator and also an ossilator called flywheel to ensure sync when tuned of a station to avoid a nasty burn on the crt tube face phospher, infact most second hand sets back then had small burn marks centre tube because they forgot to reduce brightness during switchoff : anyone over 45 will remember the bright white dot on the screen when the set was switched off

some other controls common on these sets where
local/distant = as sets didnt have auto gain control
spot wobble = the crt beam would be modulated in the vertical to produce a smother picture
audio offset = separate audio fine tune to clear intercarrier buzz in strong signal areas

 

Sorry, but you're talking complete rubbish! - sets have ALWAYS been synced off the incoming signal - the reason for frequency adjustment of hold controls was a poorly maintained TV, and the fact they used valves - which drift all over the place!.

You don't have you country filled in?, but the UK 405 system was AM video and AM sound, no FM at all. Later (and current) 625 line TV is AM video and FM intercarrier sound (6MHz in the UK, and 5.5MHz elsewhere).

__________________
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I don't think that Dean misunderstood anything, the original remark was badly expressed.

 

Nigel you are quite correct 405 line service was am video and sound when i wrote that post i should have read it before submission but alas somewhere owing to the late hour and nostalgia i got my modulations mixed up with sat systems , i have since reread it and i didnt claim that broadcasters didnt transmit sync signals of course they do but in the early days they used the mains as a timebase , tv recievers also used the mains as a time base to provide tube deflection until a station was recieved and to provide deflection should the station go of air , this was to avoid a nasty burn in on the tube face , some of the early sets where manufactured more like a cottage industry some where even built as kits from old decca and marconi ww2 surplus radar sets , another reason for using mains sync on these old sets was that unlike today where the flyback current from the yoke produces the e.h.t via a line output transformer e.h.t was produced either by stepping up the mains or some other form of inductive increase so in the absense of any sync signals eht was still present and a threat to the tube unlike todays sets where the absense of either vertical or horizontal sync can be protected by beam limiter circuits e.t.c . As for valve instability you are correct as well but i never in my post claimed that thermionic valves where stable devices in fact in my first workshop the most used tool on old sets wasnt a scope but an old pifco hairdryer fitted with a toggle switch to run hot or cold when fault finding valve stages ,you are also correct that i didnt state my country , back when i was a kid i lived in dublin the first national tv service (1959) was rte which transmitted 625 lines on vhf band 3 to most of the south and midlands , in the border counties where a lot of people had 405 line sets to pick up bbc from the north they had some small repeaters on 405 lines at band 1 and 3 the british later adapted 625 line for uhf only , Nigel i like to call a spade a spade and honestly when i recieved the email i found it extremly rude to say the least , among most tv fixers of my vintage the term used if you dissagreed with someone on a technical matter would be something like " i think you may be mistaken about that" or words to that effect , i see your profile says electronic god well im no god myself just an old tv guy , that post was my first post in this group i was trying to be friendly , there is no need to reply to this post as it is my last here .

P.s also i didnt say that sets werent synced of the incoming signal , the mains was used as sync in the absense of a transmission , and the very earliest sets did use the mains as sync thats why the hold control was used to lock the picture ,thats why there would be picture roll when you changed channel , i know valves could be unstable but not that badly when they where fully heated, later on sets improved with sync seperation due to a little device called a vic =vertical intergrater couplet module it looked like a ceramic capactor that had a bad case of the boils

 

NIGEL WROTE "You are also incorrect thinking about 'pixels', CRT's don't have pixels, they are a completely analogue device."

Sorry Nigel but i think you are incorrect on this matter , in fact abbarue is quite right in using the term pixel in relation to analog vacum tv tubes ,
Pixel : is an acronym for picture element also known as pels it defines the number of separate elements used to create an image and is not confined to digital infact it has always been around , human eyes have pixels known as rods and cones , colour tv tubes have around 44000 for a 26 inch set split rgb .
black and white tubes have trillions due to one single phosphor emulsion coat the detail only limited by the scan spot size , the term is also widely used in printing photos long before ccd and digital , ask any good tv (qualified ) engineer they'll tell you

http://members.aol.com/ajaynejr/vidglos6.htm#StartP tv video glossary

 

hello paul : this was known as hashing as opposed to hacking and it works on all high voltage tv tubes , i played about with it years ago the gear you need is simple and probably lying about your shed , 1 hf/lf reciever capable of around 10 to 15 khz , or scanner , good homebrew active attenna (plenty of designs on ham sites , 2= small portable b/w tv 3= sync injector (maybe)

you can pick up the buzz from the line stage of the target tv/monitor on your reciever then feed it with suitable coupling to the video stage in your portable , because the sync signal is to weak to pick up you can use a sync injector or some of the cheap b/w tvs have user vert and hor controls to stabilise picture , the reason the line stage gives of this info is that as the target picture causes slight voltage drop across the line tx as the picture content lightens and darkens these fluctuations can be recieved amplified and used to drive the video stage in your reciever
the screening you mentioned in the post is known as faraday caging a fine mesh of around 2.5 centimetre grid thats good at blocking signal leakage
if you try this have fun i did

 

I've been repairing TV's professionally for 35 years, (plus I was twice 'Sharp Electronics TV Engineer of the Year, and still hold the title) and am fully aware of how TV sets work.

However, I don't agree that 'pixels' can be accurately applied to a shadow mask tube, and even less to a monochrome tube. A pixel needs to be individually addressable, and CRT's aren't that by any means.

__________________
PIC programmer software, and PIC Tutorials at:
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But if a color TV tube can display any color picture as taken by a TV camera, then the color pixels have to be individually addressable or else how can the picture be shown?

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L.Chung

 

Well not many would be brave enough to disagree with professor Gordan j King .
and 35 years in tv without hearing the term pixel , maybe sharp call them pels

never seen that many sharp tvs here mostly vcr and hifi , remember one set around 1989 that came in cant remember the model number but im sure you would recognise this , it had sound and a bright white raster with flybacks , problem was a faulty rgb driver chip which was a cmos chip and unbelievably was part of the tube base my thoughts where: nice idea putting it there to cut down on noise factor but who in their right mind would put a cmos i.c less than an inch from the spark gaps , the thought crossed my mind it was someone who had just got a degree but never worked in the real world.

i wish Les Lawry johns where still alive he could have explianed that one to me !well him or the cat

 

They are shown individually as they travel through a shadow mask (delta tube) or slot mask (pil tube) its a moot point anyway the point being that the term pixel existed long before digital and even predates tv itself in printing terms

 

Never heard of him?, and wouldn't care if I had! - he can't be very important if his middle name doesn't rate a capital letter!

I've obviously heard of pixels, it's a relatively 'recent' term for the picture elements on a computer graphics card or LCD/Plasma screen. In recent times it's sometimes been incorrectly used to describe the resolution of CRT's - presumably from the resolution in the specs of computer monitors?.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

But are they(pixels) individually addressable, albeit in a sequential manner?

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L.Chung

 

you have been a tv engineer for 35 yrs 35 yrs ago king wrote most of the text books that would have been used by apprentices sitting for their city and guilds papers , he was also a chief designer for thorn emi on their tx series of sets these where the last sets ever to be made in the uk the tx100 being the most succesfull you must be familiar with the tx100 being so many years in the game .

as for old les lawry johns , well that name needs no explanation im sure an old tv man like yourself is very familiar with his name