Fuse blew when bypassing dimmer for lamp Ask questions and find answers to many subjects relating to electrics and electrical work

[brazilianx]

Hi Guys,

First-time poster. And almost never made it this far as had a scary incident this evening that I'd like some advice on please as I am a little out of depth.

So I have this nice dimmable halogen floor lamp that stopped working a while back and I thought I'd have a go at fixing it. The first thing I did was change a bulb for a new one. Still dead.

Then I changed the fuse in the plug. I saw it had a 3 Amp but as I only had a spare 13 Amp I used that. Nothing happened.

Then I thought the dimmer module might be faulty, so I opened it up to have a look, was amazed how complex it was inside, then decided to connect the light direct to a plug to take said dimmer out the equation. Put a new plug on (13 Amp) and switched on the plug. Big flash and bang, but no electrical shock to me I'm relieved to say. wasn't expecting that. (I triple checked that I had blue to neutral and brown to live, there was no earth).

I'm left wondering what could have happened and what I could do next?

Was it because I used a 13A fuse instead of the 3A that caused this? But if this happened to a 13A I can only imagine what it would have done to a 3A.

Was the dimmer module doing something critical such that it can't be bypassed (hence its sophistication - see pics below). Is it just not meany to go direct.

Why didn't the main fuse board flip?

Have I killed the light completely?

Could it be the case that a blown bulb is the root cause? They're really tricky to take out and I've already destroyed one of the delicate globe light covers.

Thanks for any advice.

[chriscba]

OMG.! That is the 12 volt transformer that you have bypasses, these lamps are designed for 12v & you put 230V through them.
So the best thing to do is, throw away the light & buy a new one.

You could of killed your self or started a fire !!

[Mr White]

Hello, what you assumed to be a dimmer switch is actually a power supply with integral dimmer. Its job is to change mains voltage (230v) to (extra) Low voltage (12v) When you by passed it, you connected mains voltage directly to the 12v lamps. The fuse blew to protect the cable. The consumers unit MCB did not trip as it was rated at 32A, the plug fuse was rated at 13A, the lowest rated device is supposed to operate first. (Which it did.)

FYI: Fuses are there to protect the cable (Most folk assume it is to protect the device on the end of the cable) You should ALWAYS use a fuse of the SAME rating, never a bigger fuse as doing so can cause the cable to heat up and cause a FIRE. You were lucky this time.

I would guess the initial problem is the power supply has failed (It is quite common) As with most things of this nature, IF you could get exact replacement parts, it will cost more than to buy a complete new light. You now have a very decorative paperweight.

I see chriscba types faster than myself.

[brazilianx]

Wow. Thanks. Close Shave
Is the light a complete write-off? What If I got a new transformer? Wouldn't the fuse blowing have stopped the damage? Or am I best quitting while I'm ahead?

[Mr White]

I already told you.

IF you could get exact replacement parts, it will cost more than to buy a complete new light. You now have a very decorative paperweight.

[chriscba]

For your own safety, just buy a new one.
Leave things like that for the experts

[ericmark]

It is an unusual set up, in general you don't dim quartz halogen bulbs. It causes early failure.

The unit that drops the voltage is more than a transformer, it also changes the frequancy, and the quartz bulbs can't be replaced with LED, so they will soon be obsolete.

So to repair looking at over £20 so as already said, better to buy new.

To be able to work with both LED needs a real transformer not electronic transformer, and the whole lighting scheme seems to have changed.

I have just been upgrading mine, I can get a colour changing dimmable wifi controlled bulb for £7.50 so nearly every lamp today is 230 volt (low voltage) not 12 volt (extra low voltage) there is little point today in using extra low voltage.