halogen lamp buzz on dimming

[Ilovelamp]

Hi, I think I need to state that I'm a DIYer? I have A-level physics and tinker with vintage audio gear but I'm no professional electrician.

Looking for advice with my floorstanding dimmable lamp. It's roughly 30 years old. It has two bulbs, an adjustable reading light that is working fine, but is a bit too dim to use on its own. The other is at the top, facing upwards, a 300W halogen light. Both bulbs have separate dimmer controls. The trouble is that when I dim the main light, it seems to work fine as it always has done, but after a few minutes (unsure of the exact time) it starts buzzing when at any setting much below full power. The buzzing is similar to the sound it once made when an insect got in there and got fried, but this time I can see no intruder, and if that was the case surely it would buzz on full power.

I've tried a brand new bulb (original stock that came with the lamp) and the same thing happens. I know I should try to find an LED alternative to both sort this issue and lower the cost of powering it, but the ones I've tried don't work with the dimming at all - they are always on and don't dim much.

The bulb is something like a 17cm long tube, with a long plastic cover over it to protect from heat. I need to find out the model number again from my ebay purchases (for the LED bulbs) but for now maybe you guys know?

Many thanks in anticipation! (I rely on this thing in the evening to get the ambiance right)

 

[i=p/u]

is the buzzing europhic effect

 

[Ilovelamp]

Quite the opposite, it harshens my buzz dude

 

[Lucien Nunes]

The buzz is caused by the chopping of the AC waveform by the dimmer, which is how the average voltage is reduced to dim the lamp. This is why it buzzes more when reduced below full power. Due to age, there might be failing capacitors in the dimmer that are affecting its operation. After a few minutes of use, the dimmer warms up, the capacitor(s) start leaking or whatever thermal effect is occurring, and the dimmer waveform goes out of whack. If the buzz is coming from the dimmer rather than the lamp, its internal suppression choke might be vibrating where the glue or tape holding the windings in place has given way.

The best solution is probably to replace the dimmer. You might need to do this anyway to use an LED lamp. The dimmer will be a traditional leading-edge control that probably won't tolerate the lower wattage of the LED (there are usually both max. and min. limits) and the LED might require trailing-edge control.

How easy the replacement will be, depends on how the dimmer is integrated with the fixture mechanically. Test the compatibility of LED and new dimmer before committing to a particular type.

 

[i=p/u]

Stop lying lucien, its knackered just.

 

[i=p/u]

Your an electrical genius lucien if i do say tho elecky bro

 

[Lucien Nunes]

its knackered

I kinda hinted at that with:

The best solution is probably to replace the dimmer.

I'm not supposed to call anything knackered because one of my claims to fame is fixing the unfixable. But I can reasonably say it's not economically worthwhile to repair.

 

[Ilovelamp]

I kinda hinted at that with:



I'm not supposed to call anything knackered because one of my claims to fame is fixing the unfixable. But I can reasonably say it's not economically worthwhile to repair.

Hey you've been incredibly informative. I'm going to print out your advice to see if my local repair guy thinks a repair is within his grasp. It's a bit beyond me. I was thinking maybe I could vaccuum the internals and spray some Servisol into the dimmer but.. no it's not a hifi amp, it looks a bit more complicated!