Noise Interference and Crackling - laptop electrics?

[jules33]

Hi,

We have an Activ64 board that was installed in December. Recently, the sound when using the laptop is very crackly and there is lots of feedback and noise. If I unplug the mains on the laptop (so it runs off battery) the noise disappears. Have tried a different laptop and different charger and this makes no difference, it's still just as noisy. However, if the laptop is off and we're using the whiteboard with the dvd player, there is no noise interference. An engineer that recently visited thought that the problem may be due to a "dirty earth". Not really sure what one of those is. Have phoned Promethean technical support and got some advice and different things to try, but wondered if anyone else has suffered similar problems.

Please post if you can offer any advice.

Thank you,

Julia

[Dug]

We had sound problems on one of our boards - but not like yours. Ours was poor sound quality and intermittently not working at all. The technician sorted it easily. One of the speaker wires (I think) was being 'pinched' by the board where it is mounted on the wall. He replaced the lead(s) and made sure they weren't fouling on anything and hey presto!
May not help you, Jules, but perhaps someone else.

[paulellis]

A 'dirty earth' usually means a dodgy connection somewhere that means that the ground/earth reference in the laptop is not the same and probably changing with respect to the reference in the amplifier.

I've had a similar problem on other audio equipment (not on a board) - it turned out to be a broken lead between the two bits of equipment.

Paul

[jules33]

We had sound problems on one of our boards - but not like yours. Ours was poor sound quality and intermittently not working at all. The technician sorted it easily. One of the speaker wires (I think) was being 'pinched' by the board where it is mounted on the wall. He replaced the lead(s) and made sure they weren't fouling on anything and hey presto!
May not help you, Jules, but perhaps someone else.

Thanks for your reply Dug - I don't think there is anything wrong with the cables, as the sound is fine when a DVD is being played on the DVD player, which is connected through the amp. I will double check tomorrow though.

It literally is fine when the charger for the laptop is unplugged - if the laptop had a decent battery, I could solve the problem by unplugging it when we use the whiteboard, but unfortunately, the batteries on our laptops are not great, so we need to run them from the mains, and that's when we get this crackly hissing feedback noise. :confused:

[jules33]

A 'dirty earth' usually means a dodgy connection somewhere that means that the ground/earth reference in the laptop is not the same and probably changing with respect to the reference in the amplifier.

I've had a similar problem on other audio equipment (not on a board) - it turned out to be a broken lead between the two bits of equipment.

Paul

Was this a broken electrical cable or speaker wire?

Thanks for your post.

[paulellis]

Was this a broken electrical cable or speaker wire?
It was the lead between my CD player and my amplifier. I was getting crackles more that 'feedback' though.

When you tried the DVD player, did you use the same lead that you plug into the laptop's audio output? Is there another power socket in range that you could try plugging the laptop's power lead into?

Paul

[jules33]

Hi,

I have found the problem - as soon as I unplugged the DVD player the noise crackles disappear. Tried a different DVD player (different make and older) and it was absolutely fine. The DVD player was a cheap one (Akura £14.99 from Makro) so maybe this is the issue?

Not sure what to do next - don't really want to buy new DVD players, and not sure if I can take them back as they are working fine - am wondering if I can get something to stop the interference?

Thanks for your posts and advice.

Regards,

Julia

[Laura OHalloran]

Hi Julia

Not an answer I'm afraid but just wanted to say that I'm pleased you solved the mystery! [clap]

Having been and witnessed the crackling noise it was all very puzzling. I applaud your tenacity in getting to the bottom of the problem - every thought about a career in Promethean's technical team? :rolleyes:

I hope that someone can come up with a solution that doesn't involve having to buy new DVD players.

Best wishes.

Laura :)

[Kimberly2905]

I just figured this out... :) Its been driving me crazy..

.I found that when my laptop is plugged into the same set of outlets that the board is plugged into I get the interference (crackling from the promethean speakers and a visual ripple when my active pen gets near the board).

When I unplugged my laptop from this set of sockets it completely went away... :) HOWEVER! whats wild is that I do have an extension cord plugged into this set of sockets which I took my laptop cord plugged on a two prong connector/adapter and plugged that into the extension cord so that I can still have power and I still don't have that problem pf crackling.....

Its working... :)

[TesteC]

hi i am currently having the same kind of problem with a newer board installed about 2 months ago really frustrating as battery life is not brilliant so having to unplug the power from the laptop is really not an option have tried everything from new power adapter to new audio cables but still get the feed back when i use the power charger any ideas on how to solve this

[kevhogg]

We experienced noticeable and unpleasant audio interference on some of our boards after buying new toshiba laptops - which turned out to a problem with our laptops. A piece of kit called a ground loop isolator (developed for car audio systems) solved the problem quickly and easily. These vary in price from under £5 to over £20 - we got ours from a well known online book retailer! If you have a similar problem - remove the power cord from your laptap - if the interference disappears then the chances are you need the kit too.