set at the factory to match the tubes shipped with the unit. So, you should never need to ever
change these jumpers unless you are changing from a 6SN7 to a 12SN7 or from a 12SN7 to a
6SN7. To set the jumpers for 6 volt operation (using a 6SN7), there should be only one jumper
installed, across 3 and 4 (you can “store” the extra jumper on pin two, so that it is not connected
to any other jumper). For 12 volt operation, one jumper should
be installed across 1 and 3, and a second jumper should be
installed across 2 and 4. If you accidentally plug a 12 volt tube
into a microZOTL configured for 6 volts, it won’t hurt it, it just
won’t work. If you accidentally plug a 6 volt tube into a 12 volt
heater, it will glow very brightly and will burn out in a few
minutes. A brief time at 12 volts usually doesn’t hurt it, except
shorten the life. It is recommended to avoid having the voltage
jumpers set wrong.
Jumper Positions
Jumper location on circuit board.
Jumper Position 1st Version
Jumper Position 2nd Version
