Ok guys heres a tough problem that I cannot figure out so here goes:

My maplin SA-909 dj mixer (from around 1999) has two VU meters (needle type not led) that im having a bit of trouble with.

The problem is this~ when I plug my denon minidisc player in or in fact anything in at line level the "main master channel switch" (main output of that channel) reads perfect and peaks at 0dB as it is supposed too, however when I flick the channels switch over to "SOURCE" (the switch that reads the incoming line level without going through the faders to check the actual line level) the db meter jumps upto about +6dB and I cannot understand why this is happening im baffled?

Any ideas anyone?

Cheers.