Back light on controls gone

[Larn]

Hi guys


I bought a polo 1.4 (97 model) everything worked fine until I got a sound system installed. a few days after that the lights which illuminate the controls, such as speedo, rev, fuel gauge, heater etc all went off, so at night i can't see any controls apart from warning lights and indicators.

I checked the fuses and as far as i can see it's not that, it can't be the bulbs because why would they all blow at the same time?

the only thing i can think of is the wiring, but i opened the cover for the dim wheel and found the wires are pluged in. there is one thick cable with a kind of scart like connecter. i thought it looks like there could be another connection, but i really don't know.

does anyone know what this might be?

thanks