im having a problem with my EH Holy Grail, when i turn the reverb knob, it just acts as volume i.e max reverb gives me no volume whatsover, or reverb, and when its at about 12 o'clock, its normal volume, but still no reverb... ive had it for just over a year, it started about a month ago. oh and it happens on all settings (hall, spring, flerb)

Anybody know whats wrong?

i just brought one home and have to tap it on the side to get it to work sometimes it's on it's way back today.