212HD reverb + tremolo problem

After searching for years I just bought a 212HD. It's in fine condition and sounds great but one thing I can't figure out: the tremolo and reverb seems to be connected to the Master volume; that is, if I set the channel volume to 10 (wich is really nice) and the Master to 2, the reverb "mix" is very low, even if set to 10. Same with the tremolo. If I set channel volume to 3 and master to 3 both tremolo and reverb works/sonds quite normal. This seems weird to me, has it been wired wrong? Anyone?

When the effects feed is "before" the master volume control, the level of effect will be proportional to the master's setting.
When the effects feed is "after" the master volume
control, the level of effect will be at maximum.