Humm, I do consider carefully which wire goes where. being colour blind I have trouble seeing the difference between dark shades of green and brown.
Humm without going it to detail I some times have to put an AC/DC module in these units I sell that are normally are just DC, the AC/DC module had an obvious earth wire to attach to the chassis then had a white wire and black wire, module has a plug for Live (presume positive) & Neutral (presume negative).
I didn't assume and called my supplier to check, just as well apparently international standards have black as the live wire and white neutral. I have put the question to electricians and they all suggested the black wire was neutral/negative, just as well I din't ask them first LOL