Practical implementation of an isolation transformer?


2004-08-06 10:26 pm
I just got a Hammond 169J for a great deal.

It's a 750 VA EI isolation transformer with a 115V primary and 90-130V tapped secondary. I would like to simply put this transformer in a large enough vented aluminum case with two duplex outlets. The box will be big enough for a future Jon Risch filter setup. I want to switch between the 110 and 120 taps as I have some vintage guitar amps which were designed when 110 was the standard, and the whole thing will also be used for safety when I work on any operating gear.

Nothing too complex for now, just IEC power socket, fuse or circuit breaker and two duplex outlets. There just a few details I need to work out.

How needed is a soft start here?

The switching arrangement I would like to use is a 15A DPDT center-off toggle switch. One pole switches the active conductor on the primary in and out, and the other pole selects the secondary tap. In this way I combine the power and voltage selector switches. For any reason should I not use the same switch to simultaneously control primary and secondary of the transformer?

Should the plugs I use be GFCIs?



2008-01-31 3:38 pm
Yeah..McDee's....quickly moving on.. ...Personally I would seperate the switching for powering-up and selecting output voltage. Don't want inulation breakdown on the switch..Or perhaps you could relay control the output voltages..