Hi guys.
Bought this unit off ebay from china a few years back now.
Worked like a champ for about two weeks when the suction suddenly died.
Been sitting for awhile but I finally got in and had a good look at it.
Nothing obvious wrong externally, but on dissassembly found diode D6 (4742 zener) to be faulty.
Replaced and suction working again.
Unit was a bit tricky to dissasemle, having to desolder the switches, but a pretty simple fix overall.
Thought I vaguely remember someone on here had the same problem a while back.
Steve.