Mac is Out of Action

I bought a cheaper non-Apple version of a charger for my MacBook when the last one blew up.  Apple products are generally very reliable, but their MagSafe Power Adapter is absolutely rubbish - I have had to replace 3 now.  That said, the non-Apple version only lasted 10 weeks.  I thought I'd check it out with my rusty electronic skills to make sure it was at fault, and not my MacBook before sending it back to Amazon.