I am replacing a faulty 110-to-220V AC transformer:
The new transformer is a Bel Signal A41-130-230. It has a little higher VA rating (130 instead of 80) and also features dual primary and secondary windings:
I have connected pins 1 and 5 to line and 2 and 6 to neutral on the primary winding (taps in parallel). I've bridged pins 8 and 11 on the secondary winding (taps in series). I measure 126.4 V AC on my line voltage. Based on the specifications of this transformer, I would expect 2X the voltage on the output, or 252.8 V AC. I am measuring 272.6 V AC across pins 7 and 12, which is about 7% higher than expected. This is open-circuit voltage (no load).
The components in this equipment are rated for 220-240V. Have I selected an improper replacement transformer, or is the voltage merely higher because it is not connected to a load?