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Illuminated power switch glows dimly when off

James Evans

Bedroom Bodger
Hi

I have an illuminated rocker switch (green if you're wondering, for my Emerald phono stage ;)) and the led in the switch glows dimly when in the off position. Not when switched off at the wall obvs.

Any idea how to sort that? When it's off I'd quite like for it to be off!

Cheers, James
 
Does it stay on forever, or is it just very slow to go? I had an amp I made that took over 30 minutes to go out. I added a drain resistor.
It stays on forever, same level of brightness. I was wondering about a drain resistor but not sure where it would go. It's just a standard DPST rocker switch with an internal LED.
 
Faulty switch by the sound of it (I don't charge for these expert opinions, BTW), with some leakage across the terminals. Replace it.
 
So you are switching live and neutral. Is the LED powered from the PSU of your circuit? As ABD says it sounds like leakage, unless you have a cap across the switch terminals and these are passing a tiny current or some such? Just doesn't seem right...
 
Is it a single or double pole switch.
A double pole will only do this if it has suppressor capacitors across the contacts
Single poles can do weird things if they are in the neutral side due to a wiring error
 
I was wondering if it was the banks of capacitors on the diy mains DC blocker potentially holding charge and leaking? There is a rasp pi on the same supply chain, so yes, there will be smps also. One thing I need to test is just plug it straight into the wall and see if it does the same there. It did the same in another room as well, but I can't remember if it was before or after the other dc blocker I have in that room when testing... (and that room also has rasp pi and shedloads of other pc/router/printer etc equipment)
 
Actually, no, I removed the dc blocker from that system, but there is an ATL EMI/RFI filter on the mains supply. Again, I'll have to test it just plugged straight into wall at some point.
 
So it's a switch with internal illumination? Which means that when the mains is connected and the switch is off there is still some voltage across the 'output'.

Is there any possibility that the switch is wired 'crossed' over? If it were wired backwards the light would be permanently on, but the switch would still switch the power. If around the wrong way then 'on' would short the mains and you would know. If neutral were connected to neutral in, live to live out etc then when the switch is off one side of the light has live and the other may find sufficient coupling to ground to cause some glow. But on would be on, and off would be off.

Seems unlikely to have happened though.

But you need to figure it out, there are potential safety hazards.
 
I did initially wire it backwards, and the light was permanently on (but power was switched as you say). I will have to double check but I'm pretty sure it's wired so live and neutral are being switched properly.
 
Sorted it, doh, one or either of wires wrong way round. That's what you get for swapping a switch in a tight space and trying to trace twisted wires by eye! Two minutes of unclipping things and problem solved.
 


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