Rek KPS6003 and Gophert NPS-1602 60V 3A PSU hack & review

[nctnico]

For a while I missed a compact, versatile solution to power various items on my bench. I have a couple of bench power supplies but these are quite bulky. I wanted something I can cram into a corner or stack on top of something else. I did consider making something with a bus which supplies 12V or 24V but in the end that is just a lot of work and not very cheap. So I started to look into compact, fanless power supplies. I started looking at the 60V 3A ones from Gophert (NPS-1602) but also found a version from Rek (KPS6003) which has a 3rd display for the power. Initially I ordered 3 KPS6003 from Aliexpress but when these hadn't arrived after 4 weeks I guessed the package got lost and ordered 3 NPS-1602 units as well (the first one arrived in 2 weeks as usual). But now the 3 Rek units also arrived which brings me to a total of 6 power supplies costing around 55 euro each. The similarity between both power supplies is striking. The major difference is that the Rek KPS6003 has a permanent display of output power and has the binding post on the back while the Gophert NPS-1602 can show the power temporarily instead of the current but does have the binding posts on the front.

There is a video of a thourough test and teardown here:




Both powersupplies come with a low voltage connection cable which is useless. Binned those. The Rek power supplies come with a Chinese power plug and a travel adapter.



I also don't like the toy binding posts and replaced them with Hirschmann PKI-110 binding posts (my standard). For that I needed to take 'm apart (Gophert left, Rek right):



It is clear that the design of the power circuitry is identical (just a different arangement due to the location of the outputs). Still I think the units are made in different factories. The one from Rek has some heatshrink around the wires to the mains voltage selector for example. I used to hotmelt glue (Dave refers to it as hot snot) to fixate and isolate the wires in a quick and dirty way while I had the power supplies open.

To get a bit more body to bolt the binding posts to the output board I soldered a couple of brass rings to the board using my hot air station:



End result on the Gophert power supply (yes, I upgraded the screws to Torx ones):



Some may say I have been putting lipstick on a pig and I might agree with that but I really like these binding posts.

I also did some testing with one of the Rek power supplies. Much to my surprise the output voltage is pretty accurate from low voltages like 1.8V all the way to 60V. On my 4.5 digit DMM the set voltage matches the actual voltage with a difference of around 30mV when the output voltage is set to 1.8V. And that 30mV is likely due to the current flowing through the ground wire between the front panel and the main board. When the value is adjusted the front panel display is dimmed and the output voltage is bang on. But as soon as the front panel display goes to full brightness a 30mV offset appears. This offset increases to 60mV when the lock LED is lit. This is probably something which can be fixed but I didn't bother. Another issue I have found is that de output voltage goes up a little bit (say 200mV) when the load switches off completely. Not a real problem because I didn't buy these PSUs to power sensitive circuitry.

Rek website: www.chinarek.com

[tautech]

 
Says he that has said he wouldn’t entertain a PSU without a numeric keypad.

[nctnico]

  You forgot the word 'bench' before PSU. These power supplies are basically high power adjustable wall-warts. In my case I likely change the voltage only a few times per year.

[electr_peter]

Quick note on cheap PSUs output terminals - they were newer superb in quality, however,  newer models have much worse output terminals (to the point were changing to better output terminals is a necessity, not just a mod).

Case in point - 2 different Gophert PSUs with visually very similar output terminals:

• Gophert CPS-3205 (older version from ~2015, 32V/5A, output on back panel, V/A setting via slide switch
• Gophert NPS-1601 (newer version from 2021, 32V/5A, output on front panel, V/A setting via button, momentary power display)

Comparing output terminals side by side quality differences emerge:

• visually both old and new look very similar, have the same style, but newer ones are slightly smaller
• new plastic knob is ~1mm shorter and narrower, visibly slightly lesser quality
• new plastic rings are ~1mm shorter and narrower, weaker parts
• new nuts are 1mm narrower (neither there or here)
• old metal shaft is turned (?), has defined sharp threads and smooth flat surfaces. New metal shaft is cast part from 2 halves with visible seams, flat spot on threads, uneven surface, questionable strength. Screws have massive free play on new version.

Obviously, manufacturer found ways to cut cost on these parts. But IMO quality of output terminals is too low, upgrade is strongly recommended.
To check output terminals on PSU without disassembly fully unscrew red/black output nuts - if flat spot on side of threads and casting seams are visible, upgrade output terminals.