- Joined
- 11 Jan 2004
- Messages
- 42,833
- Reaction score
- 2,658
- Country
Hi guys.
Got a weird one today.
Customer explains that Virgin came to fit a new cable box. The only installing they did was to swap the box over. No drilling, etc. They offered to attach the old analogue aerial so, they said, he could watch some channels without using the Virgin box. Well, the Virgin guy attached the co-ax to the TV and there was an almighty flash & the lighting fuse went.
I checked the co-ax. It did not light up with a volt stick. Scratching my head, I went round turning lights on. Sure enough, with the lounge light on, the co ax. became live, showing 224V between the outer braid and the MET of the installation. My immediate thought was a cable short between co-ax and the switched feed to the lounge light, but this seemed too simplistic. The only co-ax near the lounge light wiring is to another independent set and that does not become live when the lounge light is powered up.
The other co-ax points in the house are all live. Apparently, they are jointed under the floor, but are not routed via an amp. That was my second thought, prompted by a colleague. However, if it was a faulty amp, why is it only live when the lounge light is on?
The only other possibly relevant point is that the cpc to the lights, although present, is showing >1999 ohms on an EFLI test.
I thought maybe there's an earth fault on the lounge light and the fault current has somehow found its way onto the co-ax braid.
The fuse remains intact with the lounge light on (and therefore the co-ax at 224V referenced to earth), but if that co-ax is connected to a co-ax socket on a TV (I presume these are grounded?), then the fuse blows.
Any bright ideas?
As another colleague said, "You do get 'em, Simon...!"
Thanks in advance...
Got a weird one today.
Customer explains that Virgin came to fit a new cable box. The only installing they did was to swap the box over. No drilling, etc. They offered to attach the old analogue aerial so, they said, he could watch some channels without using the Virgin box. Well, the Virgin guy attached the co-ax to the TV and there was an almighty flash & the lighting fuse went.
I checked the co-ax. It did not light up with a volt stick. Scratching my head, I went round turning lights on. Sure enough, with the lounge light on, the co ax. became live, showing 224V between the outer braid and the MET of the installation. My immediate thought was a cable short between co-ax and the switched feed to the lounge light, but this seemed too simplistic. The only co-ax near the lounge light wiring is to another independent set and that does not become live when the lounge light is powered up.
The other co-ax points in the house are all live. Apparently, they are jointed under the floor, but are not routed via an amp. That was my second thought, prompted by a colleague. However, if it was a faulty amp, why is it only live when the lounge light is on?
The only other possibly relevant point is that the cpc to the lights, although present, is showing >1999 ohms on an EFLI test.
I thought maybe there's an earth fault on the lounge light and the fault current has somehow found its way onto the co-ax braid.
The fuse remains intact with the lounge light on (and therefore the co-ax at 224V referenced to earth), but if that co-ax is connected to a co-ax socket on a TV (I presume these are grounded?), then the fuse blows.
Any bright ideas?
As another colleague said, "You do get 'em, Simon...!"
Thanks in advance...