The trouble with some Ultrasonic cleaners [made in China ; sold on Ebay]

[wotnot]

You can read up on what led to this .

The UK safety report cites the following....




I let this be the brief for the fault condition I'm examining, and although the UK mains plug is quite different from the AU style, suffice it to say if they cut corners on the UK plug in the manner mentioned, there's every chance the AU plug got the same treatment.




Power cord 3pin plug is OK, but the IEC socket end isn't ~ see above, cord that came with the unit on the left, approved cord on the right --- note the depth of terminals in the plug molding ; with the cord that came with the unit, the active/neutral pins in the IEC receptacle only contact the IEC socket terminals for about 2-3mm ; using an approved IEC cord, this contact depth/wipe is 6mm+ ....so first step to repair is to cut IEC connector off cord and throw it away ; use an approved IEC lead instead...

I did a rudimentary continuity test between earth pin of IEC receptacle and the metal casing of the unit ~ I discovered at actual cleaning tub had no connection to earth...sigh.... dig deeper...

Turn unit upsidedown to remove 8 screws adjacent rubber feet to release bottom panel...




Place unit on side to move bottom panel and mounted electronics away out of the unit...



There's the earth wire ...it is the only one....




The earth wire itself is unmarked/unrated -- it has less cross-sectional area of copper conductors for the 'apparent' wire size ; 50% of the strands had be cut when the crimp terminals were fitted....sigh...

The earth lug is attached via a screw to the brass PCB stand-off, which itself is screwed to the bottom panel ....however.... the sheet metal is covered by that checker patterned coating ; the coating is insulation -- the only true circuit path is via the 8 screw heads/threads that I removed, and this coating hasn't been removed where the brass stand-off contacts the bottom plate....sigh....

The tub is (literally) glued into the folded sheet metal case, this is why there's no path to earth for it ....it gets better.... the two 150w/240VAC tub heaters are glued/taped to the side of the tub, N2FsG....sigh...

The IEC receptacle itself is glued in place ~ no serrated side clips holding it in the panel cutout....sigh..


Remedies: Drill tub at top (top face return of tub) to attach earth point and wire ; remove plastic coating on bottom and side panels around mounting holes for earthing bolts (4mm), attach proper gauge earth wire to IEC solder lug, and using eyelet terminations bolt all 3 earth wires to common ground point on bottom panel. Now that it's wired in accordance with the standard way of earth an appliance with all metal casings, it's likely OK to use, and certainly the GFCI didn't spit the dummy when testing.


Note: I found the fault description to be a bit odd ~ the wire used for the earth wire was like I say, right yellow/green-stripe colouring, but absolutely no markings on the sheath what-so-ever, and it was that typical 'looks like the right OD at the plastic, but only has 50% (or less) of the strands required' (and I didn't check if the strands were copper coated aluminium or not). Either way...the manner in which the unit was originally wired, I very much doubt enough current could pass down the 'earth wire' to melt it...makes no sense, so perhaps they were talking about the neutral wiring...(???...but if so, you'd likely suspect the active wiring to be just as dodgy)... in any event, I just fixed what was identified, and now I'll run the unit for a bit, and revisit it to check how the original mains wiring is holding up.

[BCNZ]

The problem with china is they just don't give a sh*t.
The only thing they care about is making money, and if means producing sub-standard equipment they'll do it.
I have encountered quite a few IEC cables where there is an earth receptacle in the female end (the brass terminal is there) but there is no wire in the cable joining it to the plug!
Also seen plenty of the female ends with the hole for the brass terminal but it's not present.
Needless to say none of these cables pass NZ (or AU) standards.
As for the crap earthing of the appliance, that's par for the course and it pays to check anything which is made in that country as it's likely to be compromised.