Any vintage amp tecs. out there?

[slicknickhaas]

I just got this vintage VOX Essex bass amp at a garage sale, not a bad amp. I plugged it in and all was working fine but as soon as I touched the line reverse switch all hell broke loose! it creates this loud low frequence buzz almost like feed back. you can wiggle the switch a bit and sometimes it gos away with little fuss but it seems to be getting worse. Its been sitting for over 20 years so I'd imagin it may need a good cleaning but my worry is that the switch may need replacing, any one else have any info or advice on this amp? I'm not finding a great deal online about them so anything is a help! thanks!

[lbpesq]

Wow, does that bring back memories.  I used to play guitar through one of these back in '74.  As I remember, it has a cool G tuner built in - a switch in back that produces a G tone through the amp.  
 
As for the switch, you might try exercising it.  Switch it back and forth (or on and of) quickly 30 or 40 times.  This may dislodge any corrosion or dirt.  If that doesn't work, I'd look inside and see if the switch is sealed.  If not, I'd spray some contact cleaner into the switch and then exercise it again.
 
Good Luck,
 
Bill, the guitar one

[xlrogue6]

Don't have a schematic for an Essex handy, but most likely that line reverse switch sends either side of the AC line to the chassis through a capacitor.  Sounds like that capacitor may be failing in your Vox (that's often referred to as the death cap because if it fails by shorting you're sending AC straight to the chassis).  If you're comfortable pulling the chassis (which can be challenging in some solid stage Voxes), you'll see a capacitor going to the chassis from one terminal of the reverse switch.  Just clip it out--in fact current UL spec precludes that cap anyway.  Highly recommend having a grounded AC cable installed and the AC supply wired to current spec (disconnect line reverse switch, fuseholder and power switch both on the hot side of the AC line) which will help prevent both big nasty life threatening shocks and little nippy annoying ones.
As long as the chassis isn't a huge pain to remove, having that done by a tech shouldn't cost too much, and while he's in there he can check the condition of the electrolytic caps also, which are always suspect in older amps, particularly when they've sat unused for extended periods.