Volteq Regulated Linear DC Power Supply GPS-1850D 20V 5A

This review is for the Volteq brand model GPS-1850D "plating and anodizing rectifier". I specify the brand and model number since lately, Amazon has been automatically merging many reviews in such a way that reviews for one product are appearing for other similar, but unequal, products.Also, while Volteq lists this as a 'rectifier', that seems to be simply a nod towards the fact that it is marketed towards the plating and anodizing applications. It is NOT simply a DC rectifier; it has all the same electronics and features one would expect from a laboratory type regulated DC power supply.I already have three nice laboratory power supplies, but I am setting up a basement workshop aluminum anodizing facility, and wanted a regulated DC power supply with sufficient voltage and current, plus current limiting, to power the anodizing, without having to move my good lab supplies down to the basement. So I wanted something inexpensive and yet still of reasonable quality.There are TONS of Chinese built power supplies out there for low prices, and I decided to use a few criteria to narrow down the choices:- A supply specifically designed for use in anodizing and plating applications, yet still useful for other random applications that might come up in my shop- Voltage and current ratings adequate for the kind of anodizing that I plan to do- Current limiting- Simultaneous digital readouts of voltage and currentI found Volteq, which sells a lot of these generic supplies under its name, operating out of a facility in California. Volteq is obviously NOT the manufacturer. The same supply is sold under the GW Instek and Mastech brand names with the same model number, as well as under other brand names with similar model numbers. The Volteq website only shows Volteq branded supplies, so I was surprised when the supply I ordered (via Amazon, but sold and shipped by Volteq) arrived with the 'Mastech' name on it instead. This goes to show you how inbred these Chinese manufacturers/suppliers are. When I called Volteq, they were not surprised that they had shipped me a Mastech branded one instead.Anyway, the supply puts out up to 20 Volts DC, at up to 5 A. In my tests, using my TekPower Programmable Electronic DC Load (also reviewed here on Amazon), the supply was not able to keep a full 20 V output when I increased the load to the full 5 A. Anything higher than 4.5 A caused the output voltage to sag, and I think it dropped to about 18.5 V at 5 A of load. So the specifications are not quite accurate......yes, it can put out 20 V and yes it can supply 5 A, but it seems that maybe it cannot quite do both at the same time. I brought this to the attention of Volteq, and their technician told me I was being unfair to the supply by using an Electronic DC Load to test it. He said if I used a big power resistor sized to draw 5 A, the supply would be able to put out the full 20V. His argument is that the electronic load I was using did not look the same to the supply as a 5 Ohm resistor would have (20V / 4 Ohm = 5 A). I could not think of why this argument would be valid, but I did not worry about it too much.I want to mention that this is a LINEAR supply, not a SWITCHING supply. This is why it costs less than some better/newer bench supplies, but as a result it is also fairly heavy and at full voltage and current will generate some heat. This is where the built-in fan comes in.My supply arrived incapable of reaching 20 V even with no load attached....as i recall it was about one volt short of 20 V. I used an external digital volt meter to check it, and found that not only was the supply not reaching 20 V, but the built in voltmeter was not reading very close to the external meter either. An email to Volteq tech support, and their technician replied with instructions and photos showing which trim potentiometer on the main circuit board needed to be adjusted to give the full 20 V, and how to calibrate the built-in voltmeter. I went further and calibrated the built-in current meter while I was at it. So don't expect these supplies to come in from the factory with laboratory level accuracy.The LED displays are large and bright, and I like them better than some newer power supply models that use LCD displays (which I think might be harder to read under some lighting situations).The supply has a small fan on the rear panel for cooling. It seems to switch on automatically when needed.The supply works on either 110 (120) V or 220 (240) V, selected with a switch on the rear panel. It is NOT a universal voltage supply, but with these two voltages it will work on most 'mains' supplies available in homes and businesses.There are two knobs for adjusting the voltage, and two more knobs for adjusting the current limiter. One knob in each set is the COARSE adjustment and the other knob is the FINE adjustment. The only way to get the full 20 V output is with the COARSE and FINE knobs both set fully clockwise. I tried to set the main circuit board's trim pot so the supply would output 20 V with the COARSE knob fully clockwise and the FINE knob centered, but it would not do so. I wanted this because I prefer to leave the FINE knob centered, then adjust the COARSE knob to get close to the desired voltage, and then adjust the FINE knob a bit from its center position to tweak the voltage. The way they designed this supply, I have to turn both knobs fully clockwise to get close to 20 V, and I consider this to be a minor design flaw.To use the current limiter feature, which is sort of a constant current feature but not in the same way as a proper constant current supply of higher cost, you turn the voltage knobs all the way down, then short the output terminals, then turn the voltage up to perhaps 4 or 5 volts, then quickly adjust the current knob(s) until the desired current is displayed on the built-in current meter, then remove the short circuit and adjust for the desired output voltage. Now if the load tries to draw more current than what you set it for, the supply will automatically reduce the voltage to prevent the current from exceeding your setting (a current/voltage relationship based on Ohm's Law). A nicer supply would make this process a bit easier, but for the low price this works well enough. Also, there is no supply that I know of that will increase the output voltage to keep the current UP TO a preset level, but such a device might exist. This supply certainly does not regulate the current UP, it only regulates the voltage DOWN. If you don't want the current limiting, just turn both of the current adjustment knobs fully clockwise.The supply has three tie posts for the wiring going to your load, and these posts can also accept banana plugs. There is a swing-over type shorting bar between the Ground terminal and the Negative terminal, and you can use it to bond the supply's Negative terminal to ground, or leave the Negative terminal floating relative to ground.The supply uses a standard IEC socket on the rear for connecting the included power cord.The other feature of this supply is the HI/LO current switch. This is not explained in the manual that I got with my supply. Volteq has a revised manual that is much less 'Chinglish' and easier to understand, and it also does not describe this feature very well. Volteq tech support told me that it is supposed to change the current-limit setting to half of your setting by simply pressing the button. I tried this, and found that while it DID reduce the setting, it was pretty far from an accurate half of my setting, and also the current meter became much less accurate in this mode. On a follow up call to tech support, I was told that this feature does not work very well, and they don't advertise it or include specifics about it in their documentation as a result. Still, it might be handy for some users.Internally, the supply is built pretty well. It has a steel chassis and outer cover, but the front face plate is entirely plastic. Up close, the appearance of the front panel is somewhat crude, as if the plastic molding, or the mold itself, was not very nicely done. The knobs on my supply are very stiff to turn, and the knobs are small and without much surface texture to improve grip, so you have to use some effort to adjust them. The output terminal posts are pretty cheap looking, but remain functional. I like the big green POWER button, and it has a good feel and requires an appropriate force to operate. The power transistor is mounted to a large internal metal plate that acts as a heatsink, and the bridge rectifier is mounted to the metal chassis as a heatsink. The main circuit board seems made well and of decent quality components. Everything on the front panel is via a second large circuit board, so the meters are not distinct from each other, they are all part of the same assembly.So I am fairly well satisfied with this supply, and it did not break the bank.