Franzus Battery Eliminator BB-333D-1

This device removes the need for batteries - it powers products rated to run on 1.5v-12vDC

I've been using one of these for a number of years now, first using the 9v battery replacement, then just straight 6v to power a radio. I haven't had any issues with the polarity switch, and I've been impressed with the longevity of it. I also was impressed by the clean power it outputs - I bought a used Casio keyboard and was trying out all the 6v power supplies I could lay my hands on, but they all produced a buzzing except this one. I ended up buying the Casio adapter because the current draw was higher than this is rated, but it was another thing which impressed me. If you want a general purpose power supply, this one is good!

The Franzus model # BB-333D universal AC/DC adaptor/charger was attractive to me because it could take input voltages of 117v or 220v and could provide output voltages of 3, 4, 5, 6, 9, or 12 volts selectable through a rotary switch. However, the usage of the +/- settings on its polarity switch is unclear. When it is set to minus, it is unclear which part of the output jack has the negative polarity.