I bought two boxed and cosmetically perfect TB-303's a couple of years ago. The guy couldn't get em to work and suspected the CPU's had died in them, but they powered up so i bought them anyway, as you would. As it turned out, after few dry joint repairs on the sync socket on one of them and a new c-mos memory chip from Roland for the other, they both chirp away just as they should!
The bargain price? £25 for the pair. Ouch.
I sold one and used the proceeds to send the other unit to Robin Whittle for the full Devil Fish treatment, which I can tell you, is a treat.