KORAD KD3005D - Precision Variable Adjustable 30V, 5A DC Linear Power Supply Digital Regulated Lab Grade…

Easy to use compact supply for the hobbyist bench. Actual dimensions are approximately 10.5" deep X 4.4" wide X 6.5" high... dimensions stated in the description are incorrect (may be that of the box).I bought 2 of the supplies so that I might work with circuits that require + and - voltages. The two units stack nicely and take up very little space on the corner of my workbench.While voltage metering is quite accurate, current readings may be a bit off on some units. In one test, I set up a 1 amp current limit on both supplies, and connected them to 3 ohm 5% power resistors. Current delivered to the two resistors, measured with a Tektronix DMM850 was quite close to the set value, measuring 1.003 amps from the upper supply in my stack and 0.994 amps from the lower unit...very accurate indeed! However, the *current reading* of the upper unit was not as accurate, indicating that the supply was putting out 1.062 amps, while the bottom unit was very close at an indicated 1.001 amps. This is perhaps not quite "lab grade" performance, but good enough for most hobby applications.I did discover one weak point in the protection scheme of the unit... while it is well protected against shorts and over temperature conditions, one must be very careful not to reverse connect to a battery capable of delivering much current. When charging and testing an 18 volt B&D battery pack, I accidentally reverse connected one unit and killed the output... it did not reset even with a power off cycle. A protection diode in the output of the supply had shorted, which did indeed protect the supply from distruction. After the diode, a 1N5480 was replaced, the unit functioned perfectly, but I might not have been so fortunate if I had reverse connected the supply to a higher current source, such as an automobile battery. Fyi, the protection diode is located on the front board very near the output terminals, so about 10-15 minutes of disassembly is required to get to it.

I looked at a lot of supplies and bought this one based on the reviews. As a retired engineer, I'm used to using the high-end stuff, but $500+ is a little much for home use. The $30-$50 units seemed too cheap and the reviews certainly reflect that. The first thing I did when I got this was to pull the cover off. I was impressed with the assembly. Good practice was used. The cables are laced (always a good sign of care being taken), the transformer is huge and the heat sinking looks good. I don't have access to a schematic, so there is no way to evaluate the design, but the innards look great.The controls exceeded my expectations and are very easy to use. The voltage displays in units of .01V and current in units of .001A. Of course, the accuracy is not that good (and doesn't need to be) but you can tweak the settings easily for fine control as needed. To adjust either, just turn the knob. Pressing the knob changes which digit it's changing (10's of volts, 1's of volts, 0.1's of volts or 0.01's of volts). Ditto for current. Note that the knob clicks but it isn't always perfect. So, for instance, to change a setting on the fly, I may select the next unit down and come at the new setting by using 10 clicks instead of one.I'll describe how to use the supply in constant voltage mode. True constant current mode is rarely used, so I won't spend any time on that. To start out, unhook all the outputs. The GND terminal is nothing more than earth ground carried though from the AC line card. It is usually good practice to connect the ground to whatever is consider "common". (Yes, I know about ground loops and the need to sometimes avoid them, but for digital work that is rarely an issue). For most of what we do, common is the "-" post, so hook it to ground. This is easy to do by using some hookup wire and making a jumper using the holes in the posts that you see when you unscrew them a little ways. Now turn on the supply and set the voltage to what you need (for example, 5.0V). Adjust the current to something you think is perhaps twice the expected current needed. This will help protect your circuitry in case something is hooked up wrong.If you now press and hold the current knob until the OCP light comes on, you will set the supply to shut down if the current limit is exceeded. If you don't do this and too much current is being drawn, the supply will enter constant current mode and just reduce the voltage to whatever is needed to push out the current set by the current limit adjustment. If this is caused by an incorrect hookup, you may at this point be frying your circuit. OCP will help prevent that by shutting down the supply. You may still end up blowing something out, but the chances are less. If the supply shuts down, you can start it up again by just tweaking the voltage knob a bit. After things are set up, press and hold the voltage knob until the panel lock comes on. This will prevent anyone (such as little curious hands) from accidently changing your settings.The meters are dual purpose. When you are turning a knob, they show the voltage or current limit setting. After a moment, they go back to reading out the current and voltage being output from the supply.I haven't evaluated parameters like regulation, accuracy, ripple, etc. If I see anything unexpected I'll update this post. Just remember the meters are not accurate to 4 digits but are pretty good (better than 1%). There is utility in having more resolution than precision. For instance, you may want to look for small current changes. My hat's off to the designers for setting them up this way. It is useful if you understand the limitations.I think it is good practice not to push any low priced supply to the design limit. I bought the 5amp model with the intention of never using it to supply more than a few amps. Current is the killer for supplies and being conservative will help it last a long time, I hope.

I have only had this unit for one day, so time will tell if it stands-up. The unit arrived with the chassis ground knob off, no big deal, screwed it back on. The biggest problem was one segment line was intermittent when turned one. You could gently tap the chassis and it would flicker on.....usually an indication of a bad solder joint. Not wanting to send this unit back, and being an electrical/electronics engineer (retired), I pulled the cover. As suspected, it was a bad joint. Hit is with an soldering iron and problem solved.The unit is well made, but the company could improve it's QA (I would of given it 5 stars if it arrived with zero problems) It should not of made it out of the factory, this joint was obvious. The unit operates well, as good if not better than supplies costing twice. Very stable and accurate. I tested the Current Limiting and Over Current Protection, both features operated as stated.The one feature I wish it had was an output enable/disable, but instead, I just pulled the banana connector when needed.I recommend this unit wholeheartedly.