Having dissected too many converters, I believe I can safely say failed capacitors are a prime reason for malfunction when they get gray hair. Then after replacing the obvious failed cap, testing of the remainder reveals none that survive a test. And unless someone has special buying power replacing the weak capacitors would bring a price tag shock. The clincher to me is the possibility of failure in the control circuit. Some manufacturers buff off component ID numbers. Integrated circuits become obsolete and have no known replacements. I do not remember seeing a detailed explanation in the forum why repairs are obsolete so I thought I'd add my one cent's worth :)