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Old 8th Nov 2020, 4:53 pm   #1
Biojem100
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Default Humming Vintage lamp

I have a vintage Pifco table lamp and the unit buzzes when the light is on.

The humming is coming from the voltage regulator, see photos.

I've checked the plug wiring and thats all fine.

Its not worth having it professionally repaired so I just wondered if anyone had any ideas?

Thanks in advance
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Old 8th Nov 2020, 5:37 pm   #2
Vintage_RC
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Default Re: Humming Vintage lamp

Looks like the "voltage regulator" is just a ballast choke and they sometimes do hum or buzz a bit.
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Old 8th Nov 2020, 6:12 pm   #3
Graham G3ZVT
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Default Re: Humming Vintage lamp

It looks like the choke is riveted to the base, but on the off-chance it's bolted, try trapping some plastic between the bracket and the laminated iron core. It may be possible to wedge something between the base and the core without any dismantling. The idea is to damp the vibration.

Odd that they've called the choke a "voltage regulator". Current regulator maybe, current limiter definitely.
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Old 8th Nov 2020, 6:33 pm   #4
broadgage
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Default Re: Humming Vintage lamp

It should be possible to replace the "voltage regulator" with a modern electronic ballast, these are virtually silent in operation. Also use less electricity and the light won't flicker.

Replacement is simple, but cannot be recommended for the complete novice due to the potentially fatal consequences of mistakes with mains voltage.
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Old 30th Nov 2020, 8:05 am   #5
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Default Re: Humming Vintage lamp

The choke looks to have a laminated core and this is likely to be the source of the noise. I have used a generous coating of varnish (NOT water based) to soak into the laminations of many buzzing cores. Give the varnish at least a week or more to set before trying it.
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Old 1st Dec 2020, 7:56 pm   #6
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Default Re: Humming Vintage lamp

Could the capacitor contribute to the buzzing if it goes off capacity or becomes leaky?
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Old 2nd Dec 2020, 1:25 am   #7
Graham G3ZVT
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Default Re: Humming Vintage lamp

Quote:
Originally Posted by Maarten View Post
Could the capacitor contribute to the buzzing if it goes off capacity or becomes leaky?
Going by how it is connected, I think that aluminium can is a glow-switch starter.
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Old 2nd Dec 2020, 8:05 pm   #8
broadgage
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Default Re: Humming Vintage lamp

I disagree, the metal canister appears to be connected in series with the choke and looks like a capacitor to me.

I see no starter.
This may be a circuit that uses the mains on/off switch to provide starting, note THREE connections to the switch rather than the two connections that would be expected for a simple on/off control.
Such circuits were popular decades ago in imported desk lamps. They work well, but had the drawback that if the built in switch is left "on" and the mains supply interrupted by some external means, then re-starting after restoring the supply was doubtful. The lamp MIGHT re start from line voltage, but not reliably.
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Old 4th Dec 2020, 1:54 am   #9
Graham G3ZVT
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Default Re: Humming Vintage lamp

Thanks broadgage, I've learned something!

I have an aquarium illuminated by an 18 inch fluorescent tube with a conventional ballast and starter, and it will happily strike without the starter installed.

I also had until recently an 8 foot fluorescent in the kitchen that had a big capacitor in the fitting, but that was wired directly across the supply for power factor correction, it must have been an industrial fitting.
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Old 7th Dec 2020, 1:03 pm   #10
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Default Re: Humming Vintage lamp

Hello.

This is my first post since joining, so I apologise if I'm 'treading on any toes'.

I have a couple of these desk lamps myself and have often wondered how they work. You are correct in that they do not have a 'glow starter' inside, but the principle of striking is the same and it does use the push button.

BTW, my apologies for the rough state of the soldering in the pics - the previous owner seemed to be a bit of a bodger!

Anyway, inside the switch unit is a small 'thimble' with what looks like a copper strap fixed to each of the 'quadrants'. Pressing the button operates a ratchet which rotates the thimble 1/8 of a revolution (at least I think it is 1/8th - fractions was never my strong point). In this operation, one of the straps engages with the open ends of the supply side of the lamp and completes this portion of the circuit. The action of pressing the button, also closes a second switch which is on the starting side of the lamp. This causes the ends of the lamp to glow (and will do so for as long as the button is held down). Releasing the button opens the starting side again and causes the lamp to strike, as in a regular fluorescent tube.

To turn the lamp off, the button is pressed again, causing the thimble to rotate again and moving the copper strap away from the circuit ends. In the event that the supply is disconnected and restored by other means, the lamp shouldn't usually restrike. The button needs to be pressed twice more - one to turn the lamp off and then a second time to recommence the starting cycle.

Simple technology I know, but I do like these old lamps.

Kind regards.

Andrew.
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Old 7th Dec 2020, 2:42 pm   #11
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Default Re: Humming Vintage lamp

A further note on these desk lamps. Mine is the smaller version, designed for an 8W T5 tube. That aside, I would suspect the switch / starting arrangements would be the same for the larger 15W model. I do have some other examples of fluorescent desk lamps in my collection. When I get a spare minute, I'll pop some photos on.

Kind regards. Andrew
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