Just a plug or heads-up about the amount of helpful information and bright folks at www.diyaudio.com . If you want to learn about equipment or theory, or you are trying to find the answer to a problem this site is heartily recommended.
Sep 112011
Feb 262011
I successfully repaired my vintage Rane AC23 active crossover. It had begun a 60 Hz hum back in late 2009 that was bothering me. I found a leaking 470 uF electrolytic capacitor in the negative voltage rail. I replaced it and its 3 brethren with some capable 1500 uF ones I had. Verified with the oscilloscope first and then tested in-circuit with speakers, amplifier and CD source. All sounds good now!
Here was the source of trouble. Oh well, they were new in 1984 so I can cut them some slack.