What/where is a flyback transformer ?
 

About 20 years ago, I paid a tech to replace a flyback on my old Toshiba 19" when the CRT went to black and nasty fumes invaded the room. I could literally see the heat waves rising out of the top ventilation slots on the rear cover.

The TV was against a white wall and I could see the heat waves distorting the air above the set. Needless to say, whenever I noticed (and smelled the problem), I moved quickly to kill the TV.

I have heard other TV techs over the years talk about the flyback, as well as you guys here on AK slinging that term about.

So, what is it used for and where is it located on a TV?

I borrowed an attachment photo from a post by Ampico-kid on his 1947 DuMont Clifton. If somebody would kindly clue me in to the function and location, I would appreciate it. Yeah, I know, I could look it up on the web, but it wouldn't be as much fun to learn. :D

The "flyback" is a transformer that operates at 15.75KHz, and serves as horizontal output transformer to drive the appropriate windings on the yoke on the neck of the CRT. And except for the very early sets the signal is further stepped up through a large number of extra windings on the flyback to the anode of the high voltage rectifier tube. The HV for the CRT anode is taken off the filament end of the HV rectifier.

The picture you offer up is taken from an angle where the sought component is not visible. In most older sets the flyback and HV rectifier are encased in a metal housing that is "fondly" referred to in the tech trade as a "doghouse", because if you reach in there you are apt to get bit. :D

Nearby, and sometimes inside the doghouse you will also find the horizontal output tube and the damper tube.

In later televisions and CRT monitors the flyback is out in the open and usually at one corner of the PC board assembly. It is usually integrated with a voltage multiplier. In most cases the quickest way to locate the flyback is to locate the CRT anode lead, and trace it back.

If you look at http://flickr.com/photos/[email protected]/photostream/ of mkoser's set you will see a metal box just to the right of the CRT neck which is the infamous doghouse.

That link didn't seem to work for me - so here's a look into the doghouse of a CTC-5. The flyback is in the upper left. The yellowish tubular part is the primary winding, and the secondary (high voltage) winding is the donut-shaped part wound over the primary.

It's called a "flyback" because it works with the horizontal deflection yoke to make the beam scan left to right across the screen and fly back to the left quickly. During the fly-back, the primary generates a half-sine-wave voltage pulse of perhaps 5000 volts in a tube color set (about 1000 volts in a transistor set), and the secondary winding multiplies this up to the 20,000 to 25,000 volts needed for the picture tube.

You can see a black wire from the primary going out of the doghouse, which goes to the horizontal output tube (not visible). The black wire from the donut goes to the high voltage rectifier tube, which then has a red wire going to the picture tube. The tube at the lower right is the high voltage regulator, which is not needed in later designs. The small tube mounted on a slant is the focus voltage rectifier.