[Boatanchors] small power transformer needed

[Brian Clarke]

Oh dear NO!!!

Robert's idea is incredibly dangerous. Any slight leak and the only current 
limiting you really have is back at your electrical mains distribution 
board - perhaps 30 A.

The other major problem you have is that you ideally want the bias to be 
with respect to the ground in your radio chassis. Such a ground will usually 
be connected to the grounding wire in your mains lead, which in turn, back 
at the distribution board, will be connected to the Neutral. The neutral is 
connected to one side of your bridge rectifier. A bridge rectifier cannot 
therefore give you a bias Voltage that can be grounded in your radio.

The only way you can safely use Robert's idea is for a temporary electric 
chair. Temporary? You may only use it once. After that, safety will be 
irrelevant.

Keep looking for an isolating transformer.

73 de Brian, VK2GCE.

On Tuesday, July 15, 2014 10:50 PM, Robert Moses declared:


> One solution might be to do away with the transformer altogether: From
> the '120' V line feed run it through a full wave bridge, then a current
> limiting resistor, and finally a large electrolytic capacitor. This will
> tend to charge the capacitor to the RMS voltage of about 165V. If you
> are dropping the DC voltage down to 95 to 125 volts this should give you
> enough to feed your dropping circuit. (BTW a 1 - 10 meg bleed off
> resistor across the capacitor is not a bad idea.)