Spectral tube holder and power supply rvfm 52 2648 this tube holder is ideal for the quick and safe setting up of spectral tubes for physics and other experiments the spectral tube is mounted from the front in the insulated holders with electrodes where the lower holder is spring loaded parallel to the tube axis the holder is provided with a power supply that can deliver 6kv dc at 2ma to the electrodes built into the base of the insulated holder rvfm spectral tube holder power supply