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RE: An Isolation Transformer

Posted by JURB (A) on April 18, 2018 at 18:30:40

In Reply to: RE: An Isolation Transformer posted by JURB on April 18, 2018 at 18:06:54:

This forum software is getting on my nerves.

I have not done the math but I got some raw numbers. I was worried about using the load with the electric heater ? Duh, just use the electric heater, which is what I did. It was nice and hot so I yanked the plug real quick like and it measures 9.4 ohms. It actually stayed pretty stable cooling down, possibly because it is an oil filled unit and perhaps conducts the heat away from the element(s) quickly. Whatever it is, it is 9.4 ohms.

With the heater disconnected the raw line voltage is 119, with the heater directly on the line it is 111. With the heater connected to the output of the transformer the line drops to 110, and the output of the transformer is 108. With the heater disconnected completely the output of the transformer is 126.

So we have input to output 119/126.
With the heater on the output we have 110/108.

So we have the line dropping 9 volts and the transformer dropping an additional 9 volts. (someting like that) If the line was constant the transformer would only drop 9 volts feeding a 9.4 ohm load, which draws about 11½ amps at 108. No doubt it is purely resistive.

I think that's not too shabby for the price. If I were working on a Carver 1.5T it would kick the triac (GAH "magnetic") regulator into full output if I drove it hard. If I had the inverting type I could load it across the hot speaker terminals with the two loads in series and drive it to full power and even test it at 4(point whatever) ohms bridged whether it likes it or not. See how that current limiting works without shorting it with a screwdriver. If not the inverting type I still have two loads to work with. Might have a problem running a large tube amp on it for a long time but then how often is that needed ? If you're not working on the hot side there is no real reason except for exposed points, which are more dangerous on the cold side usually.

Yeah, relatively satisfied with it, and nursing the backache and hernia gained by putting it in place.

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