I wish people would label things 40 years ago

[CouchPlato]

A 40 year old fluorecent tube unit has stopped working. I thought I'd have a quick look to see if I could replace it for something more modern.

No way am I going to fiddle with this. I'm going to get a professional in cos it doesn't make any sense to me.

If anybody is bored or generous enough to explain what's going on and stop my brain hurting.

 

[pete01]

Feed in and out (from previous and to next light) a feed taken to somewhere else....shaver socket or outside light maybe and switch wire....

Cant see where the wires go but something like this maybe.

 

[Mottie]

They are just feeds for other lights, aren't they?

 

[pete01]

Something like this with an extra cable thrown in.

 

[Koolpc]

Feed in and out (from previous and to next light) a feed taken to somewhere else....shaver socket or outside light maybe and switch wire....

Cant see where the wires go but something like this maybe.

View attachment 412519

Reported

 

[plugwash]

If anybody is bored or generous enough to explain what's going on and stop my brain hurting.

Lighting 101

Light switches work by disconnecting the live wire from the light, so permanant live goes to switches, switched live goes from the switch to the light. Then neutral as a return.

But we want to wire things up with cables, not single wires. So the permanent live wires are often joined inside the light fitting before going to the swtich, The switched live then comes back from the swtich to the light on the same cable.

In an ideal world the installer would have either used "twin red" for the drop to the switch, or used tape or sleeving to mark that the black wire in said cable was not in-fact a neutral. In the real world, they more often than not failed to do so.

So more than likely what you have is.

Bunch of red wires - permanent live.
Single black wire - switched live.
Bunch of black wires - neutral.