The Murata 78SR-5/2-C is a 5v 2A dc/dc converter (about $14/each at Digi-Key, which is where I got mine).
The data sheet says the output voltage accuracy is +/- 2%, so I would expect the output to be between 4.9 and 5.1v
However, I have tested four units, and under 0.1A load, they output about 4.88v, and at 0.7A they output approx 4.55v
I've tried two input sources and get the same results (plus or minus a few 0.01v) with both. They are a 24v 0.75A switching mode wall wart and a 10v 1A linear regulator. The 78SR is an efficient unit, so the input current is well within those source's capabilities.
Any thoughts on why I'm having this problem? Was I just unlucky in getting four bum units?