Checking and Replacing High Current Fuses (30xx/40xx/46xx/90xx)

The High current output of the 30xx/40xx/46xx and 90xx calibrators is protected by two in-line 30A blade fuses on the back panel assembly.

If the bridge rectifier fails, or there is a sudden surge of output current t,hese fuses can blow (or for instance if a unit set to 110V is plugged into a 240V supply)

To check these fuses, remove the outer case, and then remove the highlighted screws (there are 3 screws in each side, 3 underneath, and then 2 in the top0 to release the back panel assembly)

Hinge the back panel assembly slightly out

Look for the rubber holsters for the fuses, and then check the fuses inside. If they are found to be damaged, replace and confirm if they blow again immediately.