NANKADF WPS305H

For some time now as my bench PSU I have been using a Chinese clone Hiland DIY Power Supply kit, fed from an old 19.5V DC laptop PSU. That is until a few weeks OK when I decided to test the accuracy. I was quite shocked to find that it was not at all accurate. So on my birthday wish list this year was an NANKADF WPS305H 30 Volt 5 Amp Bench PSU.

The primary driver for the choice was that this was the cheapest Bench PSU on Amazon that had an output enable switch.

17th April - Still Work in Progress

Packaging

The PSU came very well packaged in a plain cardboard box, with a thick styrene foam cradle surrounding the front and rear of the PSU.

The box contents were

Power Supply Unit, review Below
Test Leads,
75cm figure of 8 dual black/red lead with crocodile clips at one end and 6mm open crimped 2 prong connector at the other. Not the most flexible of cables.
Mains Lead
A UK mains lead is supplied, fitted with a 13Amp fused plug, this needs to be changed for a 3A fuse immediately. It has correctly shrouded Live and Neutral prongs , however these are not brass so may heat up under heavy load. The cable thickness, 6.6mm, and it's flexibility is what I would expect of a 6A cable max, suitable for this purpose but I would not recommend using the supplied lead on a high power device.
Instruction Manual
A 14 page, B5 sized, manual. Not a lot of real information in it.

Notes

The rear panel has a 50mm exhaust fan that appears to be temperature controlled , and after spinning up at power on will stop and then not run at light loads.

There are no programmed/memory settings.

There is a configuration option which is needed to turn off the really annoyingly loud encoder beeper but it is not remembered between power cycles.

Removing the covers

First off I wanted to open the covers to check if the mains connections were wired safely before use, as I have received plenty of Neutral fused devices from China.

Removing the the top cover should have been a simple matter of removing 2 self tapping plastic screws and 6 small machine screws. Well it would be if many of them were not overtightened stripping the threads on both the machine screws and the cover. The cover appears to be 20AWG 0.9mm steel so just about enough to engage 2 turns of a fine screw thread. So after disassembly I had to find some replacement machine screws.

Incorrect Mains Wiring

If you do decide to take the covers off then be warned that the Live and Neutral cables colours are inverted and feed the wrong pins on the main board !

The rear panel mains cable socket has a built in 20mm fuse holder with a fuse marked F3AL250V that is a 3Amp fast blow fuse. UK Mains Live comes into the box via the fuse holder, then goes through a green wire to the front panel "Power" switch then back through a blue wire to the "N" connection on the main board. Neutral comes in via the cable socket and then goes through a brown wire directly to the "L" connection on the main board.

Fortunately a switch mode supply will not care which way round Live and Neutral are supplied to it. The net result is that whilst Live is both correctly fused and switched, it uses misleading wiring colours.

The Earth wire, green and yellow, from the cable socket is soldered directly to a via in the corner of the main board and then through a copper pad it is connected to a soldered bracket that is then screwed to the base of the box. The front panel earth connection is similarly routed through the opposite corner of the main board to a second bracket to the chassis. The two Earth PCB corners are not connected directly on the main board as one is on the hot side and the other on the low voltage side.

The chassis is painted black, the earth bracket screws are black anodised and no star washer is used. So this relies on the screw threads cutting into the chassis to make contact. A meter reading shows 0.2 Ohms between the incoming and front panel outgoing earth connections.

Rear Mains Voltage Selection Switch

The power supply has a 115/230V switch - so check the setting before plugging it in and turning it on the first time..

Main Power Switching Board

Front Panel Control Board

Setting Voltage or Current

On first power up the default setting is 30V and 5A but on subsequent boots it will remember that last programmed settings.

The voltage and current controls are rotary encoders and each full 360 cycle of an encoder changes the setting by 20 units/clicks. By default each click will initially change the 3rd digit i.e. 0.1 Volts or 100mAmps and will roll over the higher digits. You can change this default step by pushing the encoder switch in to change the active digit for the default step. So for example you could change complete volts first then chose to switch to single mVs.

Each click will generate a very loud beep so jump to settings, option 4, and switch this off before using it. Unfortunately this setting seems to be forgotten between power cycles

Once you have set the Voltage and Current you can push the output button to enable the output connectors.

USB Fast Charge Output

There is an orange USB socket on the front panel configured as an 18W Quick Charge supply. It will also charge non-quick charge devices at 5Volts. However the manual does not state which version (1,0,20,3,0) of the spec is actually supported.

A quick test shows it will charge my Samsung A7 tablet at 9V 800mA and my Samsung A7 phone at 9V 1350mA (which is more than the Samsung supplied charger does!)

USB Host Interface

This is shown in the manual but is not included on the supplied model

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