If you have one of these I would recommend that you have a look inside before you next use it. It may save you from electrocution.
http://www.aliexpress.com/item-img/Brand-New-PS1305-DC-Regulated-Variable-Power-Supply-30V-Softkey-Wholesale-retail/299256590.htmlCheck the wiring close to the mains switch on the front panel.
On mine there was a heat damaged ribbon cable on the low voltage side resting against the bare mains voltage connector on the power switch. There were blobs of solder still stuck to the ribbon cable insulation from when the soldering iron touched it.
I only found this by accident because out of the box it wasn't working because one of the internal non latching signal connectors has fallen off in transit. That was easily fixed, but the build quality for the rest varies between OK and truely terrible.
For example, the voltage and current pots case tags hadn't been soldered and there was flux gel still on the board.
The voltage reading was out of spec. I'm going to pull it all apart inspect, clean and reassemble before I try using using it for anything.
Mike