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Old 18th Dec 2009, 12:16 pm   #1
mattCRT
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Default Transformer Question

Hiya all,
as i am getting into tv's now, i have noticed that newer tv's have one LOPT but older sets have a big transformer and a LOPT, is the other transformer a rectifier or a frequency increasing transformer?
and why dont modern crt's have them

hope you know what i mean, as i am a little confused!!!
thanks guys
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Old 18th Dec 2009, 12:30 pm   #2
ppppenguin
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Default Re: Transformer Question

Suggest you read Steve Pendlebury's excellent website:
http://www.oldtellys.co.uk/otindex.html

Especially the section on Line timebase and EHT with its safety warnings.

Transformers are not rectifiers.
Transformers cannot increase frequency.
For an introduction to transformers the wikipedia entry is pretty good: http://en.wikipedia.org/wiki/Transformer
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Old 18th Dec 2009, 12:30 pm   #3
BassoonBloke
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Smile Re: Transformer Question

Hi Matt,

In early televisions, the line output transformer is used literally just to drive the scan coils to generate the picture, the EHT Supply usually came from a large mains driven transformer (which usually also prduced the valve heater supplies and HT's as well).
In new tv's the line output transformer drives the scan coils as above, but because the frequency is high and a lot of energy is produced, this is sent through a large 'Overwind' coil that produces the EHT voltage as well.
In both cases the EHT is then rectified and then sent to the crt.

Hope this makes a bit of sense,

Cheers,
Alan.
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Old 18th Dec 2009, 2:30 pm   #4
mattCRT
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Default Re: Transformer Question

thanks guys, now i understand better
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Old 18th Dec 2009, 3:12 pm   #5
ppppenguin
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Default Re: Transformer Question

Reinforcing the safety warning. If you are lucky enough to have a TV with mains EHT (always pre 1950, with a big and evil looking transformer) then it is LETHAL. Don't even think about working on it until you have properly understood the hazards. We are always here to help - we don't like losing forum members that way.
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Old 18th Dec 2009, 5:03 pm   #6
HamishBoxer
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Default Re: Transformer Question

No ,not always pre 1950.I have an Ultra console of a certain model that is said to have claimed a few lives.
David
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Old 21st Dec 2009, 10:04 pm   #7
TV_Madness
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Default Re: Transformer Question

As Jeff says Matt, Check out Steve P's site (amongst others) for a good heads up on the hazards associated with old tellies, not to mention the great theory sections that he has provided. It seems like steves site has been online for an eternity, as this one of the first sites that really got me into old tellies (much to my partners detriment!!)

However, you must be 101% sure before you go tinkering and that you respect the dangers that these old things can present. I was fortunate, in that I had done a City & Guilds in Electronics, so had learnt about the dangers previously (I still don't know what I'm doing!)

There are lots of good books to be found, which in my opinion are Indispensable when working with this kind of stuff.

Any Questions? Just ask.

Good luck!
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