I am currently experimenting replacing 12V dichroics with LEDs by just simply fitting into a GU 5.3 holder.
I have been told that I need to replace the 12V transformer with a LED driver but the lamp works.
Can anyone tell me what the difference between a transformer and a driver is please and what would be the possible conseqence of leaving the fitting as it is if the LED continues to work?
Thanks very much in advance.
Paul.

Depends - if the LED is 12v rated then you don't need a driver. If it's designed to run from a driver instead, then it'll go pop - the driver will be designed to control the current through the LED.

12V downlighter transformers are 12V AC on the secondary side, LED's are 12V DC. The GU10 230V LED's do not require a driver as it is in the lamp itself.

AMN

Most transformers wont cope with LED lights, but like AMN said is correct. We are testing them out where I work expensive outlay. Louis Poulsen do nice fittings which we use.

Numerous types of LED lamp are sold to replace the popular 12 volt MR16 halogen lamps.

Some types are DC only, these are primarily intended for battery operation in boats etc.
They may of course be mains powered via a suitable power supply with a direct current output, a standard halogen transformer with an AC output would not be suited.

Other 12 volt LED lamps are designed for 12 volt AC/DC supply.
These work fine from an existing halogen transformer provided that it is of the older copper/iron type and not an electronic transformer

Electronic transformers tend not to work for two reasons, firstly they have a minimum load, often 20 watts, and the LED lamps are unlikely to reach this minimum load, thus preventing the transformer operating.
Secondly, I believe that that these lamps use DC internaly with the supply being rectified. The input from a electronic transformer may be at too high a frequency for the rectifier to handle, leading to overheating and early failure.

Some suppliers "play it safe" by recomending drivers with a regulated 12 volt DC output.

Are these the "deltech" lamps as supplied by international lamps ?
If so, yes they recomend a driver, but the lamps work fine on line frequency 12 volts AC from a copper/iron transformer.
I have a few dozen working just fine.

Thank you all for your responses, very informative.
I think the general conscensus is "suck it and see".
I'll let you know in 6 months if the LED lamp is still going.
Cheers,
Paul.