Hia,

i have just read the string of information about humming and that and some good ideas there.

I am finding that i have no problems until i switch the laptop on. If it runs off the battery then fine. But as soon as i plug it in, there is an obvious hum. Would this have something to do with the adaptor, the box thats inbetween the laptop and plug.

Its definatly the computer, and i need ideas how to reduce this. I was thinking of wrapping the adaptor in something to shield the interference but then again im not sure if it is this. Any ideas? Does anyone also have this problem?

Thanks

Sounds like a problem in the Power supply. The PSU used by PC's are Switch Mode and very likely to cause problems in Audio Equipment.

Chances are, it a capacitor failing or a component used to suppress the switching action of the PSU which has already failed.

Other than following the general tips on the other thread, or trying a new PSU, there is very little you can do.

Thanks Chris,

Your input is much appreciated. You know your stuff. I was thinking of wrapping the adaptor in tin foil, but i think this may be last resort ha ha

If anybody else has this problem, please let me know.

Cheers

Olly

QUOTE

was thinking of wrapping the adaptor in tin foil

Not a Good Idea!

There is a way around the problem that NO-ONE should do *cough*. Buy an RCD and disconnect the earth, hence stopping the earth loop which is what you are hearing.
DJU HAS NOT RECOMMENDING THIS

Secondly you can buy a inline compressor, try Chris for this, failing that I can supply a link.

Nice ass by the way ADS Entertainments!!!

Sorry here comes my lack of knowledge, RCD?? stands for what??

inline compressor?? i have heard these mentioned on the forum. What do they do? and how much are they? Chris?

Ok the tin foil was not the best of ideas!!

QUOTE

Buy an RCD and disconnect the earth

Most Laptop PSU's are double insulated and don't have an earth to disconnect.

The problem, unlike Audio problems isn't earth related. Interference like this is transmitted by RF (Radio Waves) or simple magnetic fields - both which are appearing on the audio rig. chances are the laptop is also being fed with a less than smooth & regulated supply, and this is been amplified by the sound card.

Non of these solutions will fix the problem, since the interference is been fed alongside the power directly INTO the laptop.

The only solution is to have the PSU repaired / Replaced.

QUOTE

inline compressor?? i have heard these mentioned on the forum. What do they do? and how much are they? Chris?

It's Inline Supressor!!, and they won't help you in this case. Supressors filter the incoming mains against spikes and surges and do little against RF or Radiated interference.

Your cheapest alterntive is to go searching for a new PSU on Ebay

QUOTE

It's Inline Supressor!!,

Lesson one, don't try and post when your big boss is nearby and you should be working as you make silly mistakes.

QUOTE

Lesson one, don't try and post when your big boss is nearby and you should be working as you make silly mistakes

Hope you aren't posting from work and using the companies' facilities to post pictures of arses!

QUOTE (ollygeorge @ Jul 21 2003, 04:34 PM)

Hia, i have just read the string of information about humming and that and some good ideas there. I am finding that i have no problems until i switch the laptop on. If it runs off the battery then fine. But as soon as i plug it in, there is an obvious hum. Would this have something to do with the adaptor, the box thats inbetween the laptop and plug. Its definatly the computer, and i need ideas how to reduce this. I was thinking of wrapping the adaptor in something to shield the interference but then again im not sure if it is this. Any ideas? Does anyone also have this problem? Thanks

Hi
Is it a Dell Laptop by any chance?
My friend had an identical problem when connecting the charging unit to the laptop.
He disconnected the earth lead in the 13amp plug and it stopped the hum.
My laptop is ok but does not seem to have an earth lead anyway.
Not qualified to say what the implications of doing this is but best ask some who knows
Peteee l

QUOTE

Is it a Dell Laptop by any chance? My friend had an identical problem when connecting the charging unit to the laptop. He disconnected the earth lead in the 13amp plug and it stopped the hum.

Worked for me too.

QUOTE

Hope you aren't posting from work and using the companies' facilities to post pictures of arses!

Have you my boss then ?

QUOTE

Not qualified to say what the implications of doing this is but best ask some who knows

Not recomended to do this on any appliance for any reason!. By removing the earth, should any part of the metal casing become live then the item will continue to work where it would usually have tripped / blown the plug fuse.

The only way that you will find out its' live is when you or somebody else touches it. This is especially dangerous since very high voltages (300 - 400V DC) can be present in switch mode PSU's and they can arc over to the metal case in the event of a fault.

Removing the Earth is lethal, and invalidates your PAT test certificate.

Marky my roadie once got a belt off a gantry when a wire came adrift in a backbox of a bulgin socket, went a wonderful shade of green and cost me untold ammounts of lager till he felt better again. ( We since changed and rewired all the sockets and leads just to be on the safe side, but have no idea why the fuse did'nt blow)

Hola,

It is a dell, its annoying, i dont think the public know its there, but i do and thats what matters.

Im going to have a look in the plug, but i think i will stick with Chris advice, im not going to remove the earth wire, as we are dealing with the public here and how ever much i think i would like to give them a little shock. I dont think it would be the best from behind bars!!

Thanks all for your input, it has given me a really good insight into what the problem is, and that im not the only one.

Cheers


Olly

QUOTE

but have no idea why the fuse did'nt blow

Is your Gantry Earthed Spin?? - i.e does it have a physical Earth Wire connected to the mains? - or do you just rely on the lights hanging off it to do it for you?.

If its the latter then don't expect it to be properly earthed since the earth connection has to travel through the bracket and paint of the lighting fixture - not to mention the fixing you use to secure the light to the gantry .

Ideally you need a physical earth connection connected to your overhead bars at some point. If you have some form of fixed buglin junction box permanently fitted to part of your gantry then get Mark to feed an earth wire from an earth point inside the junction box, and drill a small hole in the actual bar. Then attach an M4 ring crimp to the wire and use a self tapper to secure the ring crimp against the bar. Instant Earthing!.

Thanks Chris, we actually did away with the Bulgin distribution on the bar............. but a new gantry is in the pipeline.......... my old one just won't take the weight anymore!