Part 2:I saw that a customer asked “Does the ground (green knob) connect only to the case or does it connect to the case as well as to the earth ground?” Electrical safety 101 says the green/ground post SHOULD connect to the case which should also be connected to the ground pin on the power cable, which should be earth ground. Curious as to why someone would ask, I went and checked my own power supply. My green ground post showed no continuity to the case or the ground line! MAJOR SAFETY ISSUE!!! The problem was easy to find. There is a white wire on the back of the green connector that is screwed to the case under a spacer that holds the main PCB up. When unscrewed, it was obvious that the gray paint on the chassis was effectively insulating the white wire from the chassis. (See picture). This was easily fixed with some sandpaper and now my chassis is properly grounded. HOWEVER: THIS IS A MAJOR MANUFACTURING PROBLEM AND A HUGE SAFETY HAZARD. AS SHIPPED, THE PRODUCT WAS UNSAFE AND DANGEROUS. It poses an electrical shock hazard. My unit is surely not the only unit with this manufacturing flaw. ATTENTION AMAZON and LONG WEI: YOU ARE DISTRIBUTING A PRODUCT THAT MAY CONTAIN A DANGEROUS MANUFACTURING FLAW. -Part 1:Caveat: I am not a power supply engineer, I’m just a hobbyist. My workbench is strictly low end. These are amateur observations, not a professional lab test, and this is definitely not an expert opinion. If Long Wei sees any grievous errors in my comments I will happily correct them.That said, I bought the Long Wei “PS-3010 DF” DC bench power supply from Amazon in late April 2020 for $85. (It is $15 cheaper now, October 2020.) The first thing I did after pulling it out of the box and verifying it was functional was to substitute it for a 10 volt wall wart I was using to run an Arduino project I was working on. To my surprise, the Arduino would not even run. A few minutes of troubleshooting suggested that the Long Wei was the issue, so I set it aside and went back to the wall wart. Several months later, I went back to see what was wrong with the Long Wei.The answer seems to be power supply noise. I was kind of astonished at the amount of noise on the Long Wei’s output. See Figures 1 and 2 (I labeled them “ripple”, but technically “noise” is a better term.) The main spikes of over a volt coming every 70 usec seemed (to me) excessive. The 10 MHz-centered peak in the spectrum plot seems consistent with switching power supply noise. (All my scope shots are from a Picoscope 2208B.)To give myself a reference point, I grabbed some other power sources I had laying around and examined their noise characteristics. One was an old Actiontec wall wart, another was an older Delta PC power supply. I used the same 100 ohm resistor in each case. I tested the Delta supply using both its five volt output and its twelve volt output.Refer to Figure 3 which shows the maximum, minimum, and average ac rms noise from each supply. (ignore the “Long Wei plus filter” for the moment.) The Long Wei ranged from 17.4 mV to 28.7 mV with an average of 21.4 mV. The Delta supply at 12 volts ranged from 6.86 mV to 7.03 mV noise, with an average of 6.96 mV, almost 10 dBV lower. That’s pretty significant. Not surprisingly, the Delta at 5 volts had a lower noise level, averaging 3.67 mV ac rms. Somewhat surprisingly (to me at least) even the Actiontec wall wart had lower noise than the Long Wei.I confess I don’t know how my Picoscope calculates AC rms, but the relative magnitudes are what matters here, not absolutes.Wondering if I could filter out some of the noise, I dug through my parts bin to see what I had. A few trial runs later, I was filtering the positive supply line with some 70 uH inductors and a 220 uF electrolytic capacitor. This reduced the noise (ac rms) to a range of 1.44 mV to 2.55 mV, with an average of 2.01 mV, the “Long Wei plus filter” in Figure 3, a vast improvement.I’m not sure whether this external filter introduces any instability to the Long Wei. I’m sure it is not an optimum design. (See my first caveat!) What it does show me, especially when I look at the Delta PC supply noise levels compared to the Long Wei, is that Long Wei could have done a much better job on their output filtering. But you get what you pay for and this was a very inexpensive bench supply.