Our oldest Vox we have repaired was a AC30 original with the original Mullard valves! To compliment this amplifier it had a flyer from every gig in the back dating back to the early 80s!
We love the older all valve amplifier versions, but do repair the newer VT series also with huge success. We see all shapes and sizes of VOX amplifiers broken and for repair, i suppose they're a universal amp for stage and practice.
Common Repairs to VOX amplifiers includes
Fixing crackly pots
Replacing capacitors causing hum
repairing intermittent problems with amp breaking down
Re valving and biasing
Repairing broken amplifier IC's