Light fitting doesn't work, any ideas?

[d000hg]

We've been offered two light fittings, a few years old but never used. Both feature multiple G4 20W halogen bulbs (8 in one, 16 in the other) and have built in transformers (1 in one, two in the other).

We tested these by jury-rigging to a mains plug. Neither work - you can hear a slight buzzing sound (from the transformer I assume) but no light. It seems unlikely that both would have failed, or that all 3 transformers have failed even less likely. And equally, that all the bulbs have failed in both units seems daft - these kind of units should be able to work with multiple bulbs gone, right?

Is there some obvious thing to try before we look for a friend with a multimetre?

[Lumiere]

www.diynot.com

[d000hg]

Given your username I was expecting more...

[northernladuk]

Did you buy these new?

I had two of the units we discussed in the previous thread? I replaced all the bulbs in one of mine and it stopped working shortly after. Had it on a dimmer so went through a whole mess of ordering new transformer for the unit (actually bought a new one from B&Q, swapped the transformer and took it back with the bust one in it, I know, I know... I am going to burn in hell), it stopped working again, swapped dimmers and all kinds of schizle... Anyway.. upside is the bulbs I replaced it with were too high for the unit... I can't remember the numbers, rated for 10w and I put 20w on or 20w and I put higher in... Anyhow, put the right bulbs in and hasn't missed a heartbeat since.

Check that the 20w bulbs are correct for that unit. The transformer is not rated for 200% load.

EDIT : Sorry should have read post better. Not new... Maybe some bastard swapped duff transformers out and took them back...

[northernladuk]

Don't keep turning the lights on if the there is a problem though if it is wrong spec bulbs or something is earthing their maybe a chance you haven't completely goosed the transformer. Get a multimeter to test it as soon as possible. Could.. erm.. buy one from B&Q, use it and take it back...

[d000hg]

The units are 'new' in the sense that they were bought new and then sat unused for years - the owner has never had them fitted (and is trustworthy). So I'd thought they would be the original bulbs, would it be normal for a fitting to come with bulbs?

If it was one fitting then the idea it was faulty or has developed a fault would be most likely, but two to have the same issue seems odd. Perhaps the owner bought bulbs and they are wrong, I will see what I can find out.

[doodab]

Do they have a separate switch on the DC side of the transformer?

[northernladuk]

Do they have a separate switch on the DC side of the transformer?

Mine didn't. I am guessing it looks something like this in the base (bit that attaches to the ceiling)?

[northernladuk]

Here is a good guide on what steps to take. Does the tranformer smell funny? How loud is the buzzing? I presume you are not put it through a dimmer?

How to Repair Your Halogen Lamp: 16 Steps - wikiHow

[d000hg]

Mine didn't. I am guessing it looks something like this in the base (bit that attaches to the ceiling)?

Almost identical.

The buzzing is only just audible - just enough to be sure the power is on. It is not going through a dimmer but we did wire up to a 13A plug to test plugging it in... I can't think of any reason why plugging into a socket rather than the lighting circuit would be an issue though.

Thanks for the link. I have a friend who knows this stuff but wanted to rule out dumb things (like a secret switch ) before bothering him.
I checked and the "G4 20W" is printed on the fittings themselves. I'll have to see if I can check what bulbs are actually fitted.

Question - do these kind of fittings work if we only had one bulb in or would you get an overload effect?