Protek GD0005N 5 MHz DDS Function Generator

The seller supplied it with North American power cord, which is 120V, but the unit is labeled 220V! I took the cover off and the very nice transformer inside has a label for 220V only, no dual winding. But the unit looked very nice, so I used an external step-up transformer.I like the way the control functions are designed, simple and intuitive. This generator works very, very well in every mode except square wave. However it was designed, when selecting square wave, I can hear good old mechanical relays click. That's ok, but the square wave output amplitude as well as frequency jitters around like 5%, which makes the square wave useless. Fortunately, there is an easy workaround, just select pulse mode and adjust duty cycle to 50%, which works fine. This makes me wonder why they bothered to add that relay-switched square wave in the first place.Once I got past these two hurdles, the unit works very well, in fact so well that I decided to keep it, avoid using the square wave, and replace their 220V transformer with a 120V equivalent, it's just a 50W, 1x9V and 2x18V, to get regulated 5V and +/-15V.However, I am doing this only because the selling price then was a fraction of the price which they list now. At this new price, I would not touch it, even if they fixed the listed problems.