Help! Replacing halogen transformer.

[Dave Jennings]

Hi everyone,

Hope someone can help.

Following an earlier thread on here, I found out I needed to replace the transformers on my halogen ceiling lights.

I got these ( same ones as original make ) and attached the wires on the first one - red to brown, blue to black at the first connector from the "main" cable. I then connected the other two ends which I understand are effectively neither live or neutral. I did this on only one of the non-working lights to check this fixed the problem

Which, of course, it didn't. It made it worse, in that not only did the sole remaining light now not work but there was a short BUZZ coming from *either* the transfromer itself or perhaps the light switch, it's hard to tell.

I swapped the new transformer out for the old one, and the sole remaining light worked again.

Any ideas what either I've done wrong, or if there might be some other problem I need to consider? I guess that since I swapped the old transformer back and the system works, it's not as simple as me having wired it up incorrectly.

Many thanks in advance.

[logized]

Is the new transformer the exact same model or just the same make as the old one? If not, then it may be the wrong specification or as you say the buzzing may be from the light switch - does the switch have a light dimmer? as they usually only work with electronic transformers and maybe your new one isn't?

Dave

[Dave Jennings]

logized yik-yakked:

Hi ,

Same make, same specs - model number of the original no longer in use.

Buzzing definitely from the light switch, which does have a dimmer.

Both the original and replacement transformers are suitable for use with dimmer switches.

Sorry if that makes it even more confusing!

[BigWallop]

No!!! You've got me lost. What type of transformers are they? Are they electronic or toriodial? Did the new trannies come with instructions? Help me here, I'm struggling. :-))

[logized]

Looks like there is some incompatibility even though the transformers appear to be of equal spec to the old ones. I think it would be a good idea for you to post the model and specs of the transformer, dimmer and bulb wattage here and maybe someone can pinpoint the problem.

Dave

[Lurch]

On Wed, 24 Nov 2004 15:25:33 +0000 (UTC), "Dave Jennings" strung together this:

You did connect the input and output the right way round didn't you?

[BigWallop]

It's the part about the buzzing noises he heard. Could it just have been his ears? Or was the trannie buzzing as some do and the lamp was blown? But then he says that none of the lights worked. I'm baffled to the point that my brain hurts. :-))

[Andy Dingley]

You've mixed halogens and dimmers. Don't do this.

For an easy life, don't dim them.

For good lighting, don't dim them. Halogens don't like running at half power. Switch 50W bulbs to 20W, turn them on and off in banks, but don't run them dimmed.

Don't try and dim them unless you have some reasonable understanding of electronics.

Some types of transformer (both transformers and electronic PSUs) just can't be dimmed. If you do try it, these probably work at either full or zero output, but could do anything in the middle, including some really bad letting-the-smoke-out type failures.

Many electronic PSUs can be dimmed, and dimmed easily by attaching a low-voltage variable resistor to them. If you're doing furniture or desklamps, this can be the best and simplest way of getting dimming.

_Some_ PSUs, mainly transformers, but a few of the electronics too, can be dimmed by a standard light dimmer. If it's not marked as such, it can't.

Of the few PSUs that permit it, some still don't like being dimmed (mainly the smaller transformers). They'll object by buzzing noisily. If you do have a "buzzer", try swapping the dimmer. A more modern dimmer with better output suppression may use zero voltage switching (look for a CE or FCC mark). This reduces the output harmonics that may cause buzzing.

If you're planning a dimmed installation, breadboard it first. It's easier to find that it buzzes and needs redesign _before_ you've buried the transformer in a ceiling void.

[Dave Jennings]

logized yik-yakked:

Hi

OK, my mistake on ne part - different makes as original make wasn't available from the wholesalers, but specs do seem same:

Original Transformer:

Platino brand, Model P 902

Electronic Transformer

240v, 50HZ, 60VA

20-60w

New transformer:

Lytlec brand, Model LDT 105

240V, 12v, 105VA

( Some of the specs on one don't match the other, and I'm a layman so excuse me if this means nothing, I'm just reading the figures off! )

Dimmer is standard dimmer switch, which worked with all 4 bulbs and still works on sole remaining bulb.

Using 50w bulbs.

Hope this is some help!

[Dave Jennings]

BigWallop yik-yakked:

Hi,

See post above for full details, thanks.

[logized]

The new transformer spec is plenty ok for a 50W bulb and the manufacturers claim it can be dimmed with a standard dimmer - but I think at this point it would be an idea to replace the dimmer with a standard light switch for now and get the lights working with that. If they then work ok, you would need a new dimmer - the "Standard" type is usually only rated at 250W max and as your 4 lights + transformers would probably overload it - upgrade to a 400Watt type that specifies it is suitable for dimming any type of low voltage Halogens. See this guide -

[logized]

One further note - the new transformer could be used to power 2 x 50W bulbs and this may be necessary as the above datasheet specifies a max of 3 x

105VA "normal" quality transformers can be used with a 400W dimmer.

Dave

[Dave Jennings]

Lurch yik-yakked:

OK, so this is either a serious question, or a pi**take of a numptie like myself! I'll rise to the bait, just in case.

As I understand it, the unit can be wired either way - is that wrong? The instructions don't make any mention of this, i.e. which "end" connects to the main feed and which end connects to the bulb unit. Is this the case?

[Dave Jennings]

Andy Dingley yik-yakked: ( major snippage )

Technically, the sparky who put them in originally has! And they worked fine for two years this way.

Very rarely did, usually just flicked them on full.

Both the original and the replacement are marked as "suitable for dimmers".

As for the rest of your post, I have less than no idea what it means, but it's very impressive!

Thanks for your helpful comments, I really appreciate them!

[Dave Jennings]

logized yik-yakked:

Aha. So the buzzing from the switch indicates that the dimmer unit isn't up to the mark, posibly. Cunning!

OK, I'll try that tomorrow, thanks.

[Dave Jennings]

logized yik-yakked:

OK, so if my feeble mind is taking this in, if I *do* decide to use a dimmer ( and frankly, I'm not fussed as we rarely used it anyway ) then I'd need to wire two of the bulbs into the one transformer, reducing the transformers on the "line" from 4 to 3, is that correct?

If it is, then it's too much for me, and if all I'm gaining is a dimmer I don't often use, then not that big a deal.

Or have I totally grasped the wrong end of the stick? ( Which is the likely bet! )

[logized]

They are usually clearly marked similar to this product -

should indicate which is 230V AC input and which is 12V Output.

Dave

[logized]

In that case, just fit a standard light switch and replace each faulty transformer with one of the new ones and it should save you any bother with dimmers or rewiring.

(Before you connect the new transformers - take note of the comment from "Lurch" - he has a good point about the possibility you may have connected them the wrong way round.)

Dave

[Dave Jennings]

logized yik-yakked:

Between that and the switch, I'm sure it'll be a piece of cake!

Watch out for tomorrows posting - how to repair fire damaged plasterboard!!

Thanks everyone, I'll post back how it goes.

Dave.

[Lurch]

On Wed, 24 Nov 2004 19:28:13 +0000 (UTC), "Dave Jennings" strung together this:

Quite serious, I've seen them go in the wrong way which will fry them pretty much instantly.

Yes, one pair of wires is the 230V input and the other pair is the 12V output. Get them the wrong way round and the magical blue smoke escapes!

They should be clearly marked on the transformer itself, I haven't come across one that isn't yet, and I know this because I have never read a set of instructions fo a low voltage transformer so I must have got the information off the unit itself!