Buzzing lamp

[gremlin_95]

Hi all,

I am having a bit of trouble with a desk lamp purchased from Ikea back in 2002, similar to this:

was fine for a few years and then began to make a buzzing/vibrating sort of noise which got progressively noisy until you gave it a quick knock in the base which would quieten it down.

It was no longer needed for a while anyway but now I need it and it still makes that noise.

Is there any way to stop this noise from happening? It seems to be coming from the base which I presume houses a transformer as the bulb is a 20w type which runs on 12v DC. If you hold the lamp upside down, the noise completely disappears.

Sorry if this is a repost.

Cheers

[NT]

Depends whether it uses an electronic transformer or a lump of iron.

NT

[Terry Fields]

If the lamp has a transformer that is causing the buzz, it'll be due either to loose laminations or loose windings. One way of dealing with the former to tap one corner of the laminations with a light hammer (use a drift if space is tight). I doubt there's anything you can do about loose windings.

Beware that using percussive maintenance could cause total lamp failure...

Terry Fields

[Huge]

When the transformer in my bathroom razor point started buzzing, I flooded it with superglue. It's been fine since.

[Andrew Gabriel]

or the transformer has come loose itself, or something else is now loose which can vibrate in the stray magnetic field from the transformer.

I would start by opening it up, tightening all the screws, and closing it again.

[Brian Gaff]

Its obviously loose laminations or the internal structure is ferrous and the transformer is just loose and rattling. If one can take it apart, you might see some small bits of rubber which have probably gone hard. Bear in mind that it is probably going to run quite warm, so replace the packing with something that can take that heat. if the bobbin is loose as well some heat glue might be the answer here too. It can be silenced to some extent, but you might find a bit of trial and error is required, and for goodness sake be careful if running it with the case off!

Brian

[Brian Gaff]

Chuckle, I'd not use percussive measures myself. often some form of runny laquer is a good plan, but care needs to be taken as they can smell foul when hot. I'm not convinced it will be running on DC though if its a normal bulb, but low voltage, many run on the ac from the secondary winding directly. Indeed I had one with a dimmer on it and this was basically two tappings on the same transformer.

Brian

[gremlin_95]

I opened the base up, made sure everything was securely in place and tapped it lightly! Before putting it all back together again. On switching it back on, it made a slight hum again but the noise seems to have gone completely now, for how long, I haven't a clue! But I shall report back if it continues to make the noise, if it does, I won't be disappointed; it'll give me something to do in my ridiculously long Christmas break.

Thank you for the suggestions.

[Terry Fields]

LOL

I come from a time when nearly everything had a transformer but superglue hadn't yet been invented.

Terry Fields

[The Natural Philosopher]

Dipped in hot wax or shellac

Shellac is the prime source of the Awful Smell of tortured electronics.

[Alan]

In message , Terry Fields wrote

I just used ordinary household paint/varnish and a small brush.

[Ian Jackson]

In message , Alan writes

But don't use water-based paint/varnish (which is all I had at hand at the time). I did this, knowing full well that I would have make sure that all the moisture had thoroughly dried out.

I dunked the whole transformer in the tin, and left it for a few hours before removing it and draining off the varnish. I then let it dry out in the bathroom hot cupboard for three days. Not long enough, I'm afraid. The hum was cured, but soon I heard some arcing and sparking, and wisps of smoke - transformer primary burnt out!

[grimly4]

One to watch, cheers. So whatever coating was insulating the wires was water-soluble - I'd sort of assumed it wouldn't be, but there y'go.

[Ian Jackson]

In message , [e-mail] writes

The enamel / polyurethane insulation on the wires won't be water soluble. However, 230V and dampness don't mix. I'm kicking myself for wrecking an otherwise perfectly-working transformer. There was really no urgency to stop the buzz, and I could have waited till I got some oil-based varnish (etc). It was a rather special transformer too, in a large-ish analogue 1.5A DC multi-voltage wallwart power supply. It has a secondary with switched four voltage tappings, so the chances of finding a suitable substitute are nil.