Downlight troubleshooting

[LooneyTunes]

Hoping someone might be able to assist... downlights in one of our rooms died last night. Just trying to work out what the issue is likely to be before I decide how best to tackle.

There are ~6 halogen downlights connected to a single dimmer switch. About a month ago we had the same problem of them all failing. Swapped out the switch (age unknown) for a new one. This seemed to work.

Anyway, now they died again yesterday but apparently they gave a brief flash when the OH tried them this morning.

No breakers tripped at any point and there's an extractor fan that hangs off the switched side of the circuit (that still works as normal).

My thinking is that that the transformer has probably died? What does everyone else reckon? Anything else that it could be?

If it is the transformer, is it a simple DIY job to fix? And is there anything I need to consider in terms of the spec of the transformer (i.e. are they all interchangeable)?

Thanks in advance for suggestions.

[Raverbaby]

Do they have a transformer or are they 230v(mains)downlights?
Have these always been on a dimmer or did they just start blowing shortly after a dimmer was fitted.
If you did fit dimmer, what rating of dimmer did you fit (in watts)?
If you have a spare standard light switch you could try putting that on to rule out the dimmer and double check all connections.

[crmcatee]

I would doubt if it's a single transformer feeding all the lights - especially if they're further than about 1m between them. You've probably got multiple transformers, possibly and I would make a guess at 2.

You may find that the transformers are of the type that really can't be dimmed.

I do find it rather strange that you're trying to dim the output of a switch that is also feeding the extraction fan which really is only going to run with a full load.

[LooneyTunes]

Thanks chaps - taking the questions in turn:

1) I'm assuming they're low voltage, but could be 240v (must confess, I've not checked yet but will do so in the morning)
2) Yes, they've always been on a dimmer
3) The new dimmer is 400w
4) Good idea - think there's a standard switch in the garage somewhere, will check

Agree that it is odd to have an extractor fan on a dimmable circuit - this is how the sparky fitted it though (at the same time as the lights). Some of his work has since seemed a little slapdash though, so wouldn't surprise me if someone turns round and says it shouldn't have been done like that...

[Z4monster]

I would make sure that the capacity of the dimmer is higher than the total wattage used in the lights.

I had one blow because the total wattage when all lights were on was just on the limit of the dimmer. It should have taken the total load but blew the unit in the switch.

Most have a 400W limit so you would have to get one with higher capacity if you are near this.

[LooneyTunes]

Bloody typical... ordered a new switch to swap out, and the morning it arrives the lights all start working again without me doing anything.

Must have gremlins in the attic.

Thanks for all the suggestions though!