# Why does my new 220V AC to 12V DC transformer only allow one Halogen light to work? [closed]

I'm trying to revive an old Ikea "Trettio" lighting set. The set is made up of a 220V to 12V transformer and 5 Halogen lamps connected to it in parallel.

Remembering that the original transformer was defunct, I've replaced it with a new one. Now when I connect one Halogen lamp to the transformer and turn it on, the lamp lights up. As soon as I connect another one both lamps turn off.

I've tried rotating lamps and rotating across the 5 plugs where the lamps connect to the transformer, to no avail.

Is it possible my new transformer is too weak or otherwise incompatible with the Halogen lamps?

The new transformer specs are:

Electronic Led* Converter
Prim.: 220-240VAC, 50/60Hz
Sec.: 12VDC, Max 1.25A, 15W


Each Halogen lamp's specs are:

12V 5x Max 10W


For reference, the old transformer specs are:

Electronic Transformer
Prim.: 220V-240V ~50Hz 0.26A COS 0.98
Sec.: 11.5V, Max 60W


* I know :)

• The new transformer is 15W according to the specs, enough to one and a half 10W lighbulbs. The old one was more powerful at 60W (enough for 6 lightbulbs). Mar 27, 2016 at 20:34
• Just go to the Ikea Helpdesk/Customer Care and ask for a replacement transformer. Also note how their transformer outputs sine-like wave and the other doesn't, though that's not often a problem. And that Ikea's original is very neat with cos(phi) = 0.98 Mar 27, 2016 at 21:46

2 x 10W = 20W

Which is more than 15W.

It seems the only options are buying 5 of this "converters" (one for each lamp) or buying another model which can handle more power (more lamps per converter).

• Note: It is not safe to connect the transformers in parallel. Mar 27, 2016 at 20:38
• Yes, I'll rephrase my answer to avoid missunderstandings. Mar 27, 2016 at 20:40

The new Electronic Transformer is being overloaded like Wesley Lee stated.The transformers should not have thier outputs paralleled as Turbo J said. The transformer is designed to run just one lamp because the LV wiring should be as short as possible.The electronic transformers output HF squarewave crud warts and all.There is no rectification or filtering on the chinese units that I have seen .A halogen lamp does not care about voltage waveform but LEDs of course do.If you run long low voltage wires on any low volt halogen system you will get voltage drops .The voltage drops are worse on the electronic transformer due to the high operating frequency.In other words the wiring has more inductive reactance than resistance at say 30KHz.Radiated RF interference could also be a problem with long LV wiring on an electronic transformer.

• Thanks for the detailed response. Being a newbie, would you care to explain what LV wiring, HF squarewave crud warts etc are ? :)
– urig
Mar 28, 2016 at 11:20