Exactly this. The first step for me is usually to redraw out the messed up crap the last person drafted as things that look like the design patterns. Even Tekt

Exactly this. The first step for me is usually to redraw out the messed up crap the last person drafted as things that look like the design patterns. Even Tektronix and HP can produce some dire schematics so when you've got your head in some old kit I'd probably spend more time deciphering the service manual schematics than actually fixing it (something I do as a leisure activity)