Double Insulated radio giving shocks?

[Dave Evans]

I have a background in basic electrical work but no formal qualifications other than a training course and 15 years as a Hoover engineer (washing machines).

In my 30 year experience I have encountered many item that when touched, (particularly when lightly rubbing the back of your finger over the item) I can feel a strong tingling. I realise this is because there's no earth and have also read that in some cases this is normal, but is it OK if the item is double insulated?

But is it acceptable that the 'fault' will light up a mains testing screwdriver?

I have Googled for this many times, and seen different conflicting answers. Does anyone have an explanation regards safety to use?

My latest item is a brand new small DAB/FM radio with aerial. When plugged in, the aerial will light my mains testing screwdriver. This still happens even with the power button turned off!

Any advice appreciated. Dave

 

[scotsparky]

Dave first of all i wouldnt trust the Mains screwdriver. They light up when you rub them as they pick up any static or induced current.
Is the radio class 2?? double box symbol?

From the sounds of things its static if you still feel it when the unit is unplugged. dont worry

 

[Dave Evans]

Thanks for the reply ScotsParky.

I am still concerned because I am well aware that static CAN cause similar effects, but I am confident that the 'charge' I am picking up is far more severe, and would of course discharge once earthed. It remains constant even after earthing.
Is there any way I can test so that I can prove one way or the other?

Thanks again, Dave

 

[scotsparky]

other than open it up not really. If its new send it back with your concerns and see what is said.

 

[Graeme Harrold]

Get it PAT inspected, the machine I have will detect touch currents through the casing. Worth a check if you are getting a tingle. Static tends to be a single belt discharge.

 

[scotsparky]

Graeme to pat test the casing on a double insulated unit it has tombe flash tested which can be dangerous and you have to be very carefull

 

[Graeme Harrold]

Graeme to pat test the casing on a double insulated unit it has tombe flash tested which can be dangerous and you have to be very carefull

Ive got the Fluke 6500 and it does a touch current on class 2 items. It has a sensitive probe that (strange at first) rub over a plastic case If he is getting a tingle, then there must be a few mA's flowing.........

 

[scotsparky]

i dont do pat testing so not 100% on info worth a try. Mind you if its new and under agentee send it back it may be a manufacturing fault which has to be highlighted.

 

[jreid67]

when a magnetic field passes an aerial doesnt that create a small voltage?, maybe enough to light a mains testing screwdriver?

 

[scotsparky]

Thats why i dont trust the things jreid to many false readings. They light up when rubbed on your trousers.

 

[Spudnik]

. Mind you if its new and under agentee send it back it may be a manufacturing fault which has to be highlighted.

Whats one of those then?

 

[Graeme Harrold]

when a magnetic field passes an aerial doesnt that create a small voltage?, maybe enough to light a mains testing screwdriver?

Only if its on transmit. A recieving arial should be a passive device. Ive had my hand on a 50W HF aria when it trnsmitted. didnt know at the time, but a couple of hours later I developed a mild pain across my fingers that was diagnosed as an RF burn......definately no shock

Getting a tingle, then somethings not right

 

[scotsparky]

Whats one of those then?

Its when your garente is handled by a third party. Shheeeeeeeeeeeeeeeees dont you know Engklish

 

[Guest123]

If she's double insulated then what bit of it exactly are you getting a shock from???

 

[sparkdog]

Most double insulated metal cased equipment will have a very small mains voltage on the metal partds due to the capacitance formed between the double insulation and the metal.The voltage can be detected by rubbing the back of your finger over the metal and is harmless.My old foreman when I was an apprentice electrician in the days of uneathed metal switch plates used to call it "fur"and thats what it feels like.I notice this effect on a lot of modern equipment.You could do a standard 500 volt insulation test between the mains input and the metal parts but not a flash test on electronic equipment as its liable to blow chips and things.You could also fit a permanent earth to the case and get rid of the effect altogerher.I have been a radio and telly repair man since the 1960s and still am.