What to do if your Mac beeps three times at startup
PC Beeps On Startup? Why & How To Troubleshoot It
Recognize computer beeps: 3 times, twice, on startup
Fix Computer Making Beeping Noises
boot - Computer Beeps 3 Times on Startup - Super User
Computer POST and Beep Codes
3 long beeps followed 4 short beeps and then says adapter no... - HP Support Community - 6407136
P50: Two beeps and blank screen - what are my options for troubleshooting, parts salvage, etc.? Please help me brainstorm what to do with this "bought as defect" machine. More in comments. :