Seems like amber has failed. Strange never seen it fail like that, the biggest issues I have found with 3000's have been with battery damage to denise where artifacts appear or the dreaded green screen from chip ram/agnes fails (again all from battery damage). I would pickup a new amber and try it out, it may be another component but ambers are cheap to try.
The Stock 3k power supply is fine for a maxed out system, my 3k has had all card slots full for 20 plus years.
The main 3 things any 3k user should do is, never let the battery leak, keep the cooling system clean, and make sure it has good airflow (keeping it slightly elevated on the 4 rubber legs help a good bit.). Feel the bottom after it has run awhile.
Sadly all the 3k's I have come across to fix and sell have had battery leakage.
