Multimeter (Fluke)

 The fuses on these are blown quite frequently from misuse. If you have one with a blown fuse, you will waste a lot of time.

If you put more than 1A of current through the low current input (rather than 20A input) of the multimeter, you will blow a fuse. This usually happens when you use the meter to measure current in parallel across a resistor instead of in series, but if you have a short in your circuit (if things are hooked up wrong), it can easily happen even if your meter is hooked up right.

 The solutions are to start with the 20A input on the multimemeter, before you try the more sensitive input. Also to run your circuit without the meter, and make sure it is not pulling more than 1A from your power supply (look at supply built in current meter).

To check if a multimeter current setting is bad, check continuity (with a working multimeter) through the current setting.

Replace fuse with BBS-1 or BLS-1, 1A 600V.