Bucking transformer 240v to 225v

for your precious vintage gear

by sv3ora

Did you know that you can use an ordinary transformer as a "bucking" transformer to reduce the mains voltage to a more appropriate level for your vintage gear? The technique is described in this website and it works great. The example schematic is shown below and you can of course use any transformer in hand, not just the one with the shown voltages.

I used an old UPS case and transformer to accomplish a reduction of 240V (mains voltage in my country) to 225V, to make a Collins 51S-1 internal transformer run cooler and thus saving its life. These UPS enclosures are great because they already have all the holes, plugs, fuzes and transformer needed. I used the 2x8V wiring in my transformer as a secondary and its 220V as primary. Make the connections as shown in the schematic and measure the voltage at the output. If you have connected the secondary in the wrong phase, you will see an increase in output voltage. If that happens, connect the secondary the other way round and you should measure a decreased output voltage. This technique works flawlessly and very efficiently and by using an old UPS you can build this at no cost and within a few hours without any serious labor involved. Simple, efficient and effective!

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