Vintage Voltage idea....anyone see a problem?

[SILVERGUN]

Mr. Kagliostro showed me this for lowering the input Vac to my amp....
My R+D department (1 guy who builds Tesla coils) here has "green-lighted" it,,,but I was looking for your thoughts on it....

I have been using a Variac to lower the 124vac (480 B+) coming out of the wall, down to 105vac (395 B+), and I would prefer to not have to replace the power XFMR.....I probably would just mount this "choke xfmr" inside the amp head permanently

My XFMR is a Hammond 290fx, and is way over-rated for my amp, so even the heater voltages are high, so the reduced primary voltage is perfect.

http://www.geofex.com/article_folders/vintvolt/vintvolt.htm

[sluckey]

I would build it in a small self contained box. Then you can easily use it on any amp. Radio Shack has a 12V/3A center tapped transformer that's cheap and well suited for this circuit.

[Zipslack]

Or add an internal dropping resistor or zeners....

[jjasilli]

The bucking transformer is an excellent, but maybe partial, solution.  I used it in an el84 Traynor Bassmate amp to help drop about 110 plate volts from 410 to about 300.  But it didn't get me the whole way down.  I also needed a dropping resistor in the B+ line.  I think you will too, as you seem to need to drop 20 VAC from 124 to 105.  But the 12V tranny will only drop about 12VAC.  You might use a 20 VAC bucking tranny, provided that it does not excessively drop heater voltage (I didn't do the math).  Otherwise consider the 12V tranny + maybe a dropping resistor.  That's a good combo to drop +/- 100 plate volts.  (Note that a resistor can be used to drop up to 50 plate volts, but not more; because then it begins to excessively limit current.)

[SILVERGUN]

Great stuff...thanks guys...

I'll try to zero in on the "perfect" input voltage with the Variac, and then choose the xfmr accordingly