I have a halogen light [ikea brasa 360] where the plug/transformer is missing. Image here http://imgur.com/FMjSToJ I did a bit of research and figured I could cut the cable and solder the wire to that of a plug/transformer rated at 12v. When i cut the cable on the lamp i found three wires red, yellow and blue. Given that teh transformer [from a hard drive] had only two wires I went through them all two at a time until i got a light. I joined them [yellow and blue] and the light lit but it flickers at a steady throb now and doesn't light properly. Can anyone advise as to what i need to do. As you can tell I am far from an expert in these matters. Any help would be gratefully accepted. Thanks
You have probably replaced a regulated power supply (this creates a constant 12V) with an unregulated one (which supplies 12V on average, but the actual level fluctuates). Or the power rating of the new transformer is too low.
You need a regulated power supply that can supply not just the right voltage (V) but also enough power (W).
Looking at the adapter in the photo, it shows 9.6V / 11.5V ~ .
This shows a AC output on the adapter with two voltage ranges.
Not knowing which lamp you have and if it has a high low setting, but based on the three wires and the adapter it looks like you need a dual voltage AC output adapter. Then all three wires will be used and the lamp will function proper if it has nothing wrong with it.