WD1600B012-RNN Power adaptor light goes out

Have an old 160gb external HD that I have found while moving. When plugging in the power to the unit, the light goes out and there is no power to the unit. Is there a resource where I can obtain the schematics for the circuit board of this unit (WD1600B012-RNN)? Also, if you’ve experienced this before do you have any suggestions on troubleshooting. Not interested in throwing it away, personally looking looking to repair on my own.

Thank you in advance.