jing neng jn3050p dimmer not dimming

Hard to find to replace the whole thing. Did find a site in Russia, but I doe not trust that. They charge 50+ euro!

The dimmer does work, but does not doe its main thing: dimming.
When switched on I get full power.
So: can it be repaired and which part does need replacing?

We have a good electronic-supplyshop here. All I need to know what is likely to be the defective part.