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-   -   TV Fly-Back Transformer as and Audio Transformer Anyone :) (http://www.diyaudio.com/forums/everything-else/190503-tv-fly-back-transformer-audio-transformer-anyone.html)

AB5NI 8th June 2011 06:44 PM

TV Fly-Back Transformer as and Audio Transformer Anyone :)
 
Just wondering if anyone out there has ever tried this before. A friend of mine tried it and posted a video using one as such, and it didn't sound that bad :). I was a bit "tinny" sounding, but I'm wondering if anything could be done to alleviate that problem?

Randy

Andy5112405 8th June 2011 07:03 PM

TV Flyback transformers are designed to work above the audio band, 38KHz in some instances. They will not be designed to operate at audio frequencies.

AB5NI 9th June 2011 12:06 PM

Quote:

Originally Posted by Andy5112405 (Post 2599102)
TV Flyback transformers are designed to work above the audio band, 38KHz in some instances. They will not be designed to operate at audio frequencies.

I already knew they weren't designed for audio :), but I was just wondering if they could be doctored up a bit to act "kind of correctly," let's say :) :).
The funny thing is that it's a semi-decent impedance match. Probably more work than it would be to just wind ur own, but I'm still curious if anything at all could be done. Reason: for folks/students looking to do things on the cheap and learn.

Randy

aardvarkash10 10th June 2011 05:46 AM

a flyback is not an isolating transformer is it? (unsure of my ground here...) ie the primary and secondary are in series...

wrenchone 10th June 2011 05:55 AM

Not enough core, not the right kind of core. There's a reason that audio transformers are wound on iron lams rather than ferrite. Read up and find out why.
In summary - the engineers of the world are not stupid (well some of them, at least). If there was a way to use ferrite in a real audio application, you see it all over the place, as the economic incentive would be pretty huge. The fact that you don't see it indicates that there are compelling engineering reasons that overpower the economic incentives - that should tell you something right there, as the economic incentives normally rule....

tubelab.com 10th June 2011 04:32 PM

Quote:

a flyback is not an isolating transformer is it?
Most are not isolating. The primary and the multiple secondaries are usually connected together except for the heater winding for the HV rectifier tube. Sometimes they can be carefully seperated at the terminal board, sometimes thay have seperate terminals.

Quote:

TV Flyback transformers are designed to work above the audio band, 38KHz in some instances.
The flyback transformer is pulsed at the horizontal (line) sweep rate which in the US NTSC system is 15.750 KHz for black and white TV and 15.734 KHz for color. The flyback acts as a step down transformer during the linear part of the horizontal sweep to feed the scanning energy to the deflection yoke. The linear sweep is abruptly shut off as the beam sweeps to the edge of the screen. The attempt to shut off the current through the flyback transformer will cause a high voltage pulse in the primary which is stepped up by the high voltage secondary and rectified to produce 10 to 30 KV of anode voltage to the CRT. The flyback has several secondaries, but the main ones are the step down winding to drive the yoke, and the high voltage secondary. The sweep rate is near 15 KHz and that is what is delivered to the yoke in a linear fashion. The high voltage secondary is usually resonant at a higher frequency, around 200 KHz to better deal with the sharp pulse. Consider the flyback to be a baby Tesla Coil, because IT IS!

The only place I have seen a flyback transformer used in audio is for driving a plasma tweeter. The flyback is driven at a high frequency (100 KHz +) but modulated at an audio rate.

Old TV sets often incorporated a vertical sweep or vertical output transformer to couple the vertical output tube to the deflection yoke. Many of these DO make decent quality OPT's for SE tube amps in the 2 to 5 watt range. The vertical sweep rate in the NTSC system is 60 Hz and most of the transformers work to 20 KHz. There are two styles, an auto transformer with 3 wires, and an isolating transformer with 4 wires. You want a 4 wire transformer. The wires are usually red (B+), blue (plate), green (yoke or speaker hot) and black (yoke or speaker ground). I made dozens of "Fender Champs" using vertical OPT's as a teenager.

AB5NI 10th June 2011 05:32 PM

Thanks for all the responses, guys. Well, I kind of figured they'd be a poor substitute for an audio transformer, especially with the ferite core and all not being able to handle any kind of high-power situation due to circulating currents and whatnot.

So, the veritical sweep transformer is the ticket, huh? Never knew about that one. I'll have to give one a shot and see what gives. Thanks for that info, tubelab :).

Randy

tubelab.com 10th June 2011 11:22 PM

The original Bottlehead SEX amp used a vertical output tube (6DN7) and a vertical output transformer to make a 2 WPC SE amp. It was a highly regarded Single Ended eXperimenters amp about 10 years ago. It's still being made, but the supply of vertical OPT's has dried up leading to various flavors of transformers over the years.

I don't know what is left from the era of vacuum tube TV sets. I haven't seen one in the trash dump in a while. They were common as dirt in the dump when I was a kid. I had a virtual supply of tubes transformers and everything else. The garbage cans behind the TV repair shops were always good for some tubes. Many of their discards worked fine for me. Then as now, I tended to blow them up in short order.

Late 60's vintage TV's that had 6LU8's or 6LR8's for the vertical output tube had the best transformers for audio in my early home building days. Good for a 5 watt pentode guitar amp.


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