This review is about a power supply kit I got from Banggood the other day. It is advertised as a 0-30Vdc, 2mA - 3A adjustable lab power supply. Well then, it should be able to produce 90 watts then and it only costs about 10€. That's 9W/€ then, not bad. Is it really that good?
What comes with it?
Basically the kit consists of a bag with parts and a PCB. Nothing more, nothing less. No schematics, no instuctions. You are SOL here. Fortunately all component values are printed on the PCB so building it is not a problem.
The PCB is nicely layed out. Some tracks have sharp corners though, nowadays usually not a problem, but normally it is a sign of sloppy design.
For some reason blue resistors are really a thing nowadays in China (maybe inspired by blue LEDs), but unlike blue LEDs which are just tacky mostly, blue resistors are hard to read. It is nigh impossible to distinguish red from orange. This means that you need to measure every resistor on your board to make sure you are not placing one that is a factor 10 off. The old flesh colored resistors are much easier to read.
Capacitors are quite important in a power supply so I made sure I tested all electrolytic caps that were included. The main 3300uF cap had an ESR of 0.15 ohms which is quite reasonable. Note that all caps barely met their rated capacitance. They were all in spec, but over time they will surely fall below their specified rating quite fast. I remember buying Philips capacitors 15 years ago rated at 470 uF -10%/+50% which were indeed in the 700uF range. This is a value you would never see in modern Chinese brand capacitors.
There were none. IC feet can really save your day if an IC burns out so I therefore provide my own.
Except for IC feet for the three TL081 ICs all parts are there, no complaints. The IC feet would have been a nice service for future servicability. But then they deliver the kit with extensions cables and connectors for the potmeters, which is a nice touch. There is no heatsink delivered for the main transistor, but as we are dealing here with a 90W power supply it would probably exceed the complete value of the kit anyway. Be sure to add a heatsink before performing serious load tests. There is alos no transformer included, but from the price I guess that would be obvious. You need a big beefy power transformer here. Unfortunately I have only a 18V,47VA transformer at my disposal so I will conduct my tests with that one.
To be continued...