Bucking transformer?

[Endspec]

some pics of one done with the voltages under load. no inside pics yet, next one i will do a complete photo thing on it.
Line voltage is on the left meter lol.

http://i42.photobucket.com/albums/e330/endspec/electronics/s5000735.jpg

http://i42.photobucket.com/albums/e330/endspec/electronics/s5000736.jpg

Batts died on the camra so no pics of the guts, but i did the second one for the st70 and pass 3x, filiment voltage dropped from 7.1 down to 5.9 volts and the power tubes don't look like spot lights now and the sound it even better.

 

[mikey99]

I built a bucking transformer awhile back using an old Triad filament
transformer I found which is rated at 5 Amps. I added a fuse...an
on/off switch and also a switch to select either 111V or 117V.
I fastened the transformer and a double outlet box to a piece of hardwood.

This works fine with my Scott 222B.... I keep it set on 111V.....
power transformer stays nice and cool. This freed up my variac for
other projects. I even run my Hickok tube tester through this bucking
transformer.

 

[Blast]

Nice!

 

[BinaryMike]

One of these days I'm gonna make an isolation x-former with a few windings removed from the secondary, that should solve the problem.

It may be simpler to add turns on top of the existing windings and just wire 'em in series opposing -- assuming that you have a little space between the existing windings and the core.

 

[wa2ise]

I built a bucking transformer awhile back using an old Triad filament
transformer I found which is rated at 5 Amps. I added a fuse...an
on/off switch and also a switch to select either 111V or 117V.

I added a 6.3V@6A transformer to a plug strip, and a 5 amp minibreaker. Knocks the line voltage down about 6V.

 

[Blast]

I added a 6.3V@6A transformer to a plug strip, and a 5 amp minibreaker. Knocks the line voltage down about 6V.

I like the way you dd that. That's the way I'm builidng my next one.

 

[mikey99]

I added a 6.3V@6A transformer to a plug strip, and a 5 amp minibreaker. Knocks the line voltage down about 6V.

Nice idea with the power strip ! that way you already have the
circuit breaker, switch, and outlets. The transformer I used was
a 12.6 CT so I was able to drop either 6 or 12 volts.

I used the same wiring technique on mine, read about the two
different ways to wire the bucking transformer here :

http://sound.westhost.com/articles/buck-xfmr.htm

 

[Blast]

I did like I said I would (what a concept!)- I built my second bucking transformer on a power strip ala wa2ise. The two outlets to the left are line voltage, the two to the right are down 6.3V using a Hammond 166N6 (6.3VAC center tapped secondary) from AES. It's not as pretty and cheap as the Radio Shack transformer but it's an amp higher in capacity:

 

[Blast]

--snip-- read about the two
different ways to wire the bucking transformer here :

http://sound.westhost.com/articles/buck-xfmr.htm

Good information!

 

[wa2ise]

... read about the two
different ways to wire the bucking transformer here :

http://sound.westhost.com/articles/buck-xfmr.htm

I agree with them, that the preferred way to hook it up is their Fig 4

I've also put that extra heater winding often found in Magnavox console amps to use this way. But be absolutely sure that the extra heater winding is not connected to anything before you use it here. The end result is to create a new primary with a rating with an extra 6 volts, going from 118VAC to 124VAC, and this reduces the amp's heater and B+ voltage to levels expected back when they were brand new.

 

[princeoftides]

There's always another alternative if you know the right guy and he's not afraid of getting fired. I worked at a public utility down South when I was in college and one summer it was way hot, 100 or so which was hot back then (I've seen 106 degrees in the same town recently in the newspapers.) So the tranformers were getting hot and the load on the power transformers on the poles was getting out of hand/hot so they sent a guy to the substation to dial it down about five volts or so to reduce the load so things didn't start blowing everywhere. So if you know the right guy that would be willing to dial it won at the substation....Oh, just kidding. He'd get caught in no time flat. But sometimes they do that.