Mastech Dual DC Regulated Power Supply 0-50 V @ 0-5a

I purchased " Mastech Dual DC regulated Power Supply ". When I plugged the power cord in and turned the switch on, nothing happened. No light, no nothing. Then I tried to plug it in many different power oulet, it still did not turn on. So I called Kaito, and they told me to return it back. After waiting a few weeks and no feed back, I called them back to find out what is going on?. They said that they are about ship it back to me today. And also they told me that the reason the power supply will not turn on in the first place because they forgot to switch from 220 to 210 power system(made in china) before they ship it to customer. Their little mistake cost me time and money to return it back. Therefore I would not recommend this to other customers. This power supply looks like a toy. The knobs do not seems to be last long.

Not having purchased a personal power supply before, I found this option to be very tempting. I'm not familiar with Mastech, but have a customer that had this unit, and it's stable enough to power general electronics and has great features for the price. I have read several warnings in the literature about being careful to unplug devices such as spinning motors, etc., that would provide power back into the unit if it was shut off or powered down at the wrong time. I guess it doesn't have protection from backward voltages or ?? (Sorry, I'm a mechanical guy, not electrical... know enough to do what I need to do). As long as I'm careful with potential energy sources mixed into the system, I expect no problem. I'd buy from Mastech again. I rated it 4 stars only because I'd expect a premium product to protect itself without having the user be concerned.