HeNe Laser Power Supplies in Series or Parallel?
So you have a couple of HeNe laser power supply bricks for use with 1 to 2 mW HeNe lasers and someone just gave you a 5 mW HeNe laser head. Is it possible to use the two in series or parallel instead of buying or building a suitable power supply? Larger HeNe tubes require much more operating and starting voltage, and possibly more current as well. The current difference is of less consequence than the voltage difference. For example, a 5 mW tube may have a nominal current rating of 6.5 mA but will probably run just fine on 4 or 5 mA (though a higher value ballast resistor may be needed to maintain stability). However, the 5 mW tube will require about twice the operating and starting voltage of a 1 mW tube (thus requiring a series connection if such a kludge is possible at all). Whether the power supplies can be hooked in series or parallel depends on their design. The inverter types in particular (which includes all bricks), could become mighty unhappy. I wouldn’t recommend connecting
