I presume you mean the EZB board fuse. If you have a multimeter or buy a cheap one then put it in series with your PSU/Battery on the amps range. Then see what the current drawn is with various servos or whatever operating. If you see a big jump in the current drawn you have found your problem

I suspect the current draw will be greater than 5 amps. Try unplugging different sensors/servos/etc to diagnose which one is shorting.

Give us a list of the sensors and servos you are using. Also, what is the EZ-B mounted on? That could be shorting.

Thanks for the help. I think the problem was that the EZ-B was resting on a screw which was causing the short.

Now if only I can figure out why my HC-SR04 keeps overheating....

Post pics of your connections and soldering. If it's over heating, then there is an issue with power. Since the board was shorted severely, you should also check to ensure the voltage regulators are still working correctly. Check for +5 on the I/O pins between +5 and GND.

I'm using 4 F/F jumper wires to connect the HC-SR04 to two I/O ports. I've triple-checked the connects: VCC to +5 (D15), Trig to PWM (D15), Echo to PWM (D16), GND to GND (D15). I've tried switching the Trig and Echo as well. My jumper wires are color coded so no chance of a mix-up. Same thing every time: work until distance goes to 255 and IC chip behind the T gets REALLY hot REALLY fast.

Just checked the EZ-B with my multimeter and registering +5.01V between the +5 and GND so all good there.

Thoughts?

Is the hcsr04 attached to anything? Hot glue or sticky tape? Adhesives are mostly conductive.

Not attached to anything yet. Haven't gotten beyond pinching it between my fingers to test it.

That's strange. I'd suggest it was defective, but the fact that it works - partially - is confusing. What kind of battery source are you using?

6 freshly charged AA Sanyo eneloops for a total of 7.2 volts.