I know, that this topic is not new, but I thought I could give new users a short and comprehensive idea how to modify their Mana SE boards in order to
install some remedies to the problems when the Arduino Nano's pins are temporarily floating (e.g. when switching between T2Laser's two application panes), so
1. solve the LaserON problem (10k resistor between GND and S-pin)
2. solve the hissing of the motors (they get shortly enabled = get current flowing through their windings, luckily without getting DIR & STEP pulses) by a 10k resistor between +5V and D8).
I also hotglued and soldered male connectors to the board to wire 3pin homing switches (the ones which come with the LEDs), so that they are connected to +5V, GND and D9 of the Nano. You could also just use GND and D9 when using switches not soldered on the board with an LED. In the case that you are using these LED equipped switches +5V is needed and then you MUST REMOVE the NC-pin of the switch!! see:
http://benboxlaser.us/index.php/topic,1494.msg21588.html#msg21588, reply #77.
In the first pictures you see the modified homing switches which I use and a blue LED with a 1k resistor in series, plugged into the motor output connector. This allows me a very safe testing instead of having the laser connected all time.