Flashing low power light

[jks]

I've just replaced the landing light with a 60w low power one. The light is switched from downstairs and upstairs. In one of the "off" settings the light flashes every 3 - 4 seconds, in the other "off" setting it doesn't. The cable between the switches is Y (240) B R G (earth). The flashing occurs when the red and blue are connected to the light side of the circuitry.

I assume it is capacitance between the cables that is causing the problem. Apart from rewiring with separate cables is there any other solution.

John

[mmzz]

It can be a problem with the cheaper bulbs. Try a more expensive one

[jks]

This one was free from PowerGen

[mark]

It's got to be a Philips one, they have recently admitted to a problem with the faulty starter circuit in the 18w variety. They are currently exchanging then for people if you contact them via the website.

[Calvin]

I too think you're seeing the effect of capacitive coupling (aka crosstalk or pickup) between the individual wires in the cable. It's interesting that you observe it only in one of the two "off" states - I think I can see how that can happen - not that I can offer a fix though. The cable is probably 3-core and earth which is usually arranged as colourA-earth-colourB-colourC across the cable. I don't think that the coupling will be between colourA and one of the other colours as the earth will supress it. That means that colourB and colourC are coupling. My guess then is that when you don't see the effect colourA is connected to the lamp with colourB and colourC as live feed and connected to the switch. In the other off state colourB and colourC are live feed and connected to the lamp, hence the coupling.

Other posters have suggested that more expensive CF bulbs don't do this

- I wonder if they have bleed resistors? [In fact maybe there's a DIY solution there - a bleed resistor across the terminals of the fitting].

[jks]

It is a Philips. - 60w equivalent.

"Genie 6yr 11w"

[jks]

I measured the voltage using an analogue meter from the light side to earth. The voltages were 40v and 75v in the two "off" positions (light removed). I think the cable arrangement is

123e. 2 and 3 connect live in one state ( capacitance is 2 - 1) and 1 and 3 in the other (capacitance 1 - 2 and 2 - 3).

[Calvin]

A 123e arrangement would be very unusual. Every cable I've ever seen has the earth in the middle. Anyway I think the only solution is a bleed resistor of low enough value to stop the cap in the CF lamp from charging or a lamp with one built in. That said I've lived with our landing light doing the same thing for years and I can't see that it's a problem worth fixing.