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jwil1
02-08-2008, 12:22 PM
How safe is it to run a computer/monitor on an extension cable without an earth pin??

I would think it would be dangerous - what do you guys think??

Reason is that when the computer concerned is plugged in and audio run through a sound system an 'earth hum' is heard.

rumpty
02-08-2008, 12:56 PM
Under the setup you describe, I'm surprised that you get an "earth hum", because the only earth on the whole system would be on the sound system. That single earth is the best arrangement to avoid a hum loop.

Perhaps there is still an earth on the computer somewhere that you have overlooked?

As for the safety aspect, you should really have the computer/monitor earthed somewhere.

jwil1
02-08-2008, 01:20 PM
Thanks for that.

I too thought the only earth should need to be/is on the desk, but the whole system is very old (20+ years!) and it is dying.

It needs to be replaced, but it's a church... you know church finances... :groan:

tweak'e
02-08-2008, 02:32 PM
do not operate an extention lead without the earth pin, you never know what the lead will be used for next.

if your getting hum through its usually due to earth loop. any aerial connected to the sound system ?

either fix the gear or fit an isolator on the audio cable between pc and sound system.

Erayd
02-08-2008, 02:35 PM
...but the whole system is very old (20+ years!) and it is dying...Good grief! Would you be willing to share the specs? Actively using a 1988-era computer in this day and age must be interesting...

jwil1
02-08-2008, 02:45 PM
The cable is "meant" to be used only with the computer when sound is needed. But in this church multiboxes and extension leads grow legs fast...

The PC is only 3 years old :)

The sound desk is 20 years old. It's a Peavy Unity Series 2000 or something.

Caked with dust and crackles when any knob is adjusted. As I said, dying!

Horrible, HORRIBLE desk to work with.

Looks like this one, but is dustier
http://www.trademe.co.nz/Music-instruments/Pro-Audio-DJ-Equipment/Mixers/photos/a-166565411/p-72193506.htm

tweak'e
02-08-2008, 03:14 PM
have you tried a different pc ?

jwil1
02-08-2008, 03:27 PM
I have used my laptop straight to the desk which is OK-ish (fades in and out sometimes - not my laptop lol), but have not tried it through the same cable the computer uses.

Any thing else I should be aware of?

BTW it wasn't my idea to create an unearthed lead. I have refused to run my laptop unearthed - I need it and don't want to fry it!!

AFAIK the main prob with this situation is the sound desk. I'm not sure about the state of the cables, but I know the desk is well past it's use-by date. Is there anything else I should test before I try to get them to spend some $$?

Agent_24
02-08-2008, 04:31 PM
It needs to be replaced, but it's a church... you know church finances... :groan:

That surprises me, what with not having to pay taxes and all...

nofam
02-08-2008, 04:42 PM
That surprises me, what with not having to pay taxes and all...

No taxes, but not much revenue either!! :p

tweak'e
02-08-2008, 05:30 PM
laptop won't have an earth so theres no worries with that ;)

Sherman
02-08-2008, 07:50 PM
laptop won't have an earth so theres no worries with that ;)

Beg to differ, but some do. Like my Compaq for instance.