[R-390] Isolation Transformer update

[Scott, Barry (Clyde B)]

<snip>
> And, measure the voltage at the transformer.. For low bulb 
> brightness, it 
> will be close to line (applied) voltage. At higher 
> brightness, it will drop 
> substantially -- you may have had only 90 volts on the transformer.
> 

Yes.  I did notice the input voltage at the xfmr was around 100V and
fluctuated a bit.  I assume the bulb does not provide a constant resistance
at the low currents.

> Your current measurement may be fooling you. the thing is 
> VERY reactive at 
> no load, so that 500 ma may be well out of phase with the 
> applied voltage. 
> You certainly should not expect to multiply the 500 ma by the 
> transformer 
> input terminal voltage to get the dissipated power.  A one 
> ohm resistor in 
> series and a dual trace scope to watch voltage and current is very 
> instructive here.
> 
> Roy
> 

The 561 is only single trace... :(


Barry(III) - N4BUQ