Whirlwind MCT7 - Multi Connector Cable Tester - Manual (Page 6)

To change the battery, you will require a Phillips head screwdriver. Remove the
four screws located on the bottom of the MCT-7 Cable Tester as shown in Fig. 3.
To remove the battery, turn the unit upside-down and carefully remove the base-
plate.
Remove the battery from the unit being careful not to strain the battery leads.
Disconnect the battery and connect a new one. Position the newly connected battery back
in the unit and reassemble with care.
We recommend that you use only alkaline type batteries, to prevent any type of
leakage that may damage the MCT-7 Cable Tester.