PURPOSE: To facilitate withstand-voltage processing based on variations of electron guns by enabling only one of set-up tabs, which are prepared by quantity corresponding to kinds of electron guns and connected to each other by use of string, to be connected to each corresponding plug.

CONSTITUTION: While a case 46 is equipped with plugs 45 by quantity corresponding to kinds of electron guns, set-up tabs 47 movable up and down are arranged, with each of them being 1:1 corresponding to each plug. Set-up tabs 47 are connected to each other by use of string 51, and only one of them is connected to each corresponding plug 45, through rollers 49 and 50. While a socket 19 of an electron tube 11 is connected to the plug 45, with power supply 24 being connected through the case 46, a discriminator 55 consisting of a reflection tape 54 and sensor 56 discriminates the kinds of electron guns and control power supply 28. Therefore, only pushing down a set-up tab 47 enables withstand-voltage processing of various kinds of electron tubes to be made, then improving work efficiency widely.