Please see
https://www.eevblog.com/forum/projects/a-small-experiment-part-one/msg2788726/#msg2788726 for part one of this story when I order the power supply.
Well, it arrived this morning which makes it about two and a half weeks from China to Germany, nice quick service. The power supply was well packed in an unmarked cardboard box and the usual gray China Post plastic bag. The sticker on the base of the supply gives the input voltage (110V-245 V) and the output voltage (5 V 2 A) but nothing else. no safety markings and no CE mark. The power lead is 45 cm long with a 5.5 mm plug on the end.
96 V AC was measured between the negative terminal and mains earth. This figure dropped to zero when a 100 k resistor was added between the two points.
The results of the output tests are as follows:
No Load
Output 5.345 V DC with 120 mV of 140 KHz noise on top of the DC and it's nasty spiky stuff which will interfere with radio reception.
1A Load (50%)
Output 5.163 V DC with 300 mV of 158 KHz noise on top of the DC. The power supply ran cool for thirty minutes during this test.
2A Load (100%)
Output 5.08 V DC with 447 mV of 185 KHz noise on top of the DC. The power supply was slightly warm at the end of the thirty minute test but not hot.
Summary
I got what I paid for, a cheap 5 V supply to power a desk light. It needs additional filtering on the output to reduce that noise and I actually get 5 V at 2 A which is a pleasant surprise. This supply will probably be OK for logic work but I wouldn't consider it for test and measurement work or powering an audio amp.