Comment by fastneutron

Ludlum is rare among equipment manufacturers in that they design with user-servicability in mind. They happily took phone calls and emails from my 16-year-old self about how to diagnose and repair various instruments of theirs I had picked up on eBay, many of which were long obsolete. Their schematics are still open, to my knowledge.

I have no relation to the company, just a very satisfied customer.