Numark Cm100 Failed Pat Test

[DJ Sacha 0]

Hi all,

 

I know this is the wrong forum but I am unable to post in the techie forum - most likely due to my low post count.

 

My band had all its gear PAT tested yesterday and as I'm the drummer/DJ my DJ rig was tested too. Currently I own a Numark D2 Director with a Numark CM100 mixer. The D2 Director passed the PAT test - well its power adaptor did - but the CM100 failed for not having an earth.

 

I called my local DJ store - DJ Supplies in Kidderminster - to ask them if this was a common issue. They said that the mixer could be double insulated and if it were they'd be a "square within a square" symbol at the back by the power input. Well I checked last night and there isn't. However, I did notice somethings that were odd for what I thought was a UK spec product:

 

* the AC input spec is 115/230v

* the unit is certified to CAN/CSA STD

* the warnings etc are in English and French.

 

Now I'm of the opinion that this CM100 was sourced from another zone - either North America or Europe or wherever uses the 2 pin mains plug. The unit also has an external ground too. My dad - who is an electrician - has opened the unit up and confirmed that there is no earth and that 2 pins on the IEC chassis are not connected to anything. He needs to identify the correct earth pin with his meter before doing anything else - sorry for being vague but if he typed this he would explain that better then me!

 

I purchased the unit from an online UK supplier and I'm just wondering if it is possible that they have been flogging non-UK spec kit. I know that it's not an issue and I don't intend to go moaning at them but not having a mains earth is a bit scary as I always have a mic connected to the unit. I also remember that when I bought the unit - 2 years ago - it came with a mains 2 pin plug to IEC.

 

Where I work - in IT - we order in a lot of Cisco switches for our datacentres - now because the UK distributor takes so long we normally end up with euro-zone switches that are supplied by the likes of Misco or Insight. They're also happen to be cheaper then the UK supplied units. I'm just wondering if this is the same scenario as with mixers etc.

 

Finally, could the lack of earth explain the following issues:

 

* Low quiet hum through the PA when the mixer is on

* totally obvious loud hum when a light is connected to the BNC socket on the mixer...

 

or am I talking complete rubbish!

 

Your thoughts would be appreciated.

 

DJ Sacha

 

 

 

Update

 

 

 

My dad has connected up the earth from the earth IEC pin to the chassis of the mixer. The low hum has now gone and the obvious hum when the BNC light is connected has now gone too. Also the "tingle" sensation - I didn't mention this before - when touching the case and something else electrical has also gone too.

 

I always seemed to get a "tingle" off the case if my arm rested against it whilst touching my Dell laptop touchpad. The case being what the D2 and CM100 are racked in - obviously felt this when everything was powered on.

 

 

[Andy Westcott 0]

Quote:

"I always seemed to get a "tingle" off the case if my arm rested against it"

 

Ahh... This is the old mens' way of tesing for a live chassis on the old style AC/DC TVs.

 

Doesn't mean the chassis was live in your case though - if it was, you'd have blown a fuse when the earth was connected, and you'd probably be dead before now anyway. This is a very very small leakage current which may be the result of excessive damp within a double insulated device, a supression capacitor connected to chassis or simply a device which should have been earthed in the first place. It sounds like the latter to me.

 

This is a potentially serious situation, and the dealer really needs to be made aware of the details, although I'm not sure how much notice they'd take.

[Danno13 0]

This is a know problem with this range. My cm200usb also fails a PAT test, though if you connect a link from one of the phono grounds to something else thats grounded properly within your console case then it'll pass.

[otronics 0]

Glad to know all is well now.

 

Some dual CD players (for eg) have a 3 core mains lead but the earth is not connected to the casing.

 

In fact, I posted about it last year when getting my stuff PAT tested. For it to pass, I had to get inside it and solder on an earth terminal.

[Norfolk DJ 0]

I also have a Numark Cm100 bought on-line but from a European supplier.

 

It's fairly new, but noticed that the plug has blown 2 fuses over thenpast 6 months. I'm not sure why becuase i've had no other problems with it.

[superstardeejay 0]

This seems to be a storm in a teacup to me.

 

Many grey imports (and some legit stuff) which is double insulated doesn't have the symbol on there, though of course it should have. It's quite common to fit an IEC inlet and then not internally connect the earth pin if it's not required. The earth stud on the back is of course a signal (audio) ground and is just for screening any turntable decks to the mixer chassis to prevent hum.

 

The shock you may have had leaning across laptop/mixer is more likely to have it's origin in the laptop, since these are notoriously high-leakage devices thanks to their switch-mode power supply and EMC filtering. You just felt it on the mixer because the mixer would have been earthed via your amplifier and was thus the shortest path from the laptop, through you and down to mains earth.

 

Numark, being an American company, are well aware of the ramifications of sending out equipment of dubious safety (American markets being particularly letigious with their accident-compensation economy) and are pretty much as safe-a-bet as any major brand.

 

 

[otronics 0]

This seems to be a storm in a teacup to me.

 

Indeed and almost catch 22. Double insulated with 3 core mains but no earth connected to chassis but this fails the PAT test. Connect earth to pass PAT test but perhaps no need.

[superstardeejay 0]

Some dual CD players (for eg) have a 3 core mains lead but the earth is not connected to the casing.

 

Probably more to do with interpretation of which class the appliance is by the testing person. Double insulated stuff can of course use an IEC 3 core lead and just not have the earth pin connected...it's still double insulated if it's been designed this way. Missing the symbol from the rear doesn't make the unit any more dangerous..just confusing. Remember its mainly the UK who are PAT test mad, but then again we're the country of red tape and health and safety.

 

 

 

[Andy Westcott 0]

Quote:

"You just felt it on the mixer because the mixer would have been earthed via your amplifier"

 

Of course... I was half asleep as usual.