77 replies to this topic

[ciderbooze]

The dc ground can be commoned with the a.c. earth and is sometimes but does not have to be for the ground to exist. They are two very different things.

[higgins]

there will be no ac earth on these sort of appliances as they are doubley insulated. my guess is it is the rectifieror a dodgy capacitor

[vocky]

I will measure mine and see what it's kicking out 

 

[vocky]

holy crap .......... 47 volts AC that's chassis to mains earth point

Edited by vocky, 04 November 2013 - 10:25 PM.

[slindborg]

I, ah, thank you

[vocky]

tomorrow I will be checking inside the ctek and see how it's been wired, I suspect the neutral and live might need swapping over

[slindborg]

Tbh I doubt its that. Check the mains between the neutral and earth

[ciderbooze]

I, ah, thank you

Implying the dc ground has to be derived from the a.c earth is still just plain wrong though.

[slindborg]

Neutral not earth, but still, it can't be helping as in vockies case there is a 47v pd between the car and house when plugged in.

[ciderbooze]

I have seen similar behavior on systems that have a commoned ground and earth with a bad connection back to earth. The input filters that modern equipment have dump to earth and without a good earth quite high voltages can be seen.

[turbobob]

So, pray tell, where does the charger derive its '0v/ground' from then...... Do we atleast agree its not that the 12v and ground have been swapped magically

Mains inlet is probably only magnetically coupled to the rest of the circuit via a transformer. So not electrically connected. 

[ghand]

So, pray tell, where does the charger derive its '0v/ground' from then...... Do we atleast agree its not that the 12v and ground have been swapped magically

Mains inlet is probably only magnetically coupled to the rest of the circuit via a transformer. So not electrically connected. 

I agree , I will go with your switch mode power supply output circuit filter theory, slight ac ripple on the dc Oh and it could be a high frequency ripple so forget what the multi meter says, or is that just made up rubbish

Edited by ghand, 05 November 2013 - 10:30 AM.

[TheRealVXed]

I reckon it's a raspberry ripple Gordon.

 

Check the freezer.

[siztenboots]

add a ground strap to the chassis?

[ghand]

I reckon it's a raspberry ripple Gordon.   Check the freezer.

[Hammy of hamhouse]

Depending on the design there may not be a transformer and isolation from the mains supply . So as neutral voltage is closer to zero volts ( earth potential) reversing live and neutral can give that buzzing feeling

[turbobob]

When the circuit is made, neutral will not be at 0 volts. And any design of mains to DC supply will have to be isolated for safety reasons. 

 

 

[vocky]

mains plug only has neutral and live, no earth wire (two core mains cable). I opened up the ctek and it does have a mini transformer, however the neutral is connected via a capacitor to the 0v of the output. So unable to swap the AC input over, well I am not connecting the chassis to mains live !

[turbobob]

Wtf vocky? Capacitors pass Ac. Are you sure about that? Typically the dc side is derived from the output of the transformer then it is totally 'electrically' isolated. Only magnetically coupled. 

[vocky]

there is a wire on the PCB coming from the neutral terminal which goes to a capacitor, which then connects to the 0v of the output (DC)

 

I will take a picture 

 

 

Edited by vocky, 05 November 2013 - 08:45 PM.