by EWBrown » Mon Aug 28, 2006 6:08 am
One method that I use is to connect the OPT primary to low voltage AC (use a filament or other AC "wall wart" transformer, the voltage doesn't really matter, as long as it's 24VAC or less. The important part is to never connect directly to the AC power mains.
Measure the AC voltage across the OPT's primary, and then across the secondary (8 ohms), and write down the readings.
The primary impedance is (voltage across primary / voltage across secondary)^2 X the secondary impedance.
Example, 16.00 VAC across the primary, and 0.506 VAC across the secondary. (I use a variac and 16VAC transformer and can fine-tune the input voltage)
16.00 / 0.506 = 31.62
The ratio works out to 31.62 ^2 or 1,000:1 therefore the secondary impedance would be 8,000 Ohms.
Important Caveat:
Never connect the low voltage AC across the OPT's secondary, as the primary will then have very high voltage across it, and this will probably burn out the trannie, as well as create a shock hazard.
/ed B in NH
Real Radios Glow in the Dark