Power Transformers as Mod Transformers

[WA4WAX]

K3BGX shares his experience with us. Interesting tips.  Please see pg. 110-111.  Have fun!

http://www.americanradiohistory.com/Archive-Electronics-World/60s/1960/Electronics-World-1960-05.pdf

[w8khk]

K3BGX shares his experience with us. Interesting tips.  Please see pg. 110-111.  Have fun!

http://www.americanradiohistory.com/Archive-Electronics-World/60s/1960/Electronics-World-1960-05.pdf

Matt, check out this link:

http://www.amwindow.org/tech/htm/tvtomod.htm

Tim, WA1HLR shows us how it has been done.

73, Rick

[WA4WAX]

Rick:

I saw that before.  Thought people might enjoy the old article as well.

Take care!

[W1RKW]

K3BGX shares his experience with us. Interesting tips.  Please see pg. 110-111.  Have fun!

http://www.americanradiohistory.com/Archive-Electronics-World/60s/1960/Electronics-World-1960-05.pdf

what a coincidence, at the end of this article is an announcement of the Tri-City Amateur Radio Council monthly meeting in my area.  Today they are called the Tri-City Amateur Radio Club.

[Opcom]

Power iron has been used many times for audio output iron as long as the windings are a decent match. A 100W 6146-based solenoid driver for a Faraday cell for example in Scientific American NOV 1970. It made use of two 6.3V 15A windings in series to drive the coil and the 800V winding as the primary. (schematic shows a stock part since the experimenter's part might not have been common) Menno Vanderveen wrote a helpful article about frequency response, power, and power bandwidth. "secrets of output transformers"

[W1AEX]

When I was building my 4-400 x pair of 833's I ended up following a schematic Steve WA1QIX guided me through to use a big plate transformer in a push-pull heising modulation scheme. It has worked beautifully and actually offered some asymmetry by connecting the plates of the 833's to a pair of lower voltage taps and the heising components to one of the higher voltage taps. It sounds pretty good and I doubt anyone would guess that it's not a modulation transformer in there.

Rob W1AEX

[flintstone mop]

I had a horrible experience buying a used Elmac AF 67 from another ham op. The mod transformer was blown and an expensive replacement mod transformer from some rip-off place in New Jersey that motivated me to use a power transformer. And that little Elmac sounded so sweet with a pair of 6550's, a power transformer from a high power stereo tube amplifier and a Heizing Reactor. I followed the link for Timmy's, WA1HLR, tutorial from the AM WINDOW. Amazing positive peaks. The Elmac drove my AL1500.
I remember Tim stating that the transformer needs to be something that was pretty big. A tiny thing used in an older tube receiver would not cut it.

Fred

[steve_qix]

I have definitely used power transformers as mod transformers with very good results.

You HAVE to keep the DC out of the transformer by using a coupling cap and choke (so-called modified Heising).

Rob mentioned "Push-Pull Heising".  This works VERY well - used it for years until building a pulse width modulator and finally ditching the transformers altogether.

Some transformers have taps on the secondary (like a 6000VCT tap and a 5000VCT tap).  If you put the mod tubes on the low tap, and then take the modulation from the high tap (using a capacitor and a Heising choke), you will be able to achieve quite high positive peaks.