Members ivorycj Posted September 2, 2015 Members Share Posted September 2, 2015 Hi all, I have a Kurzweil PC3X that has been repaired by 2 technicians, only to have the same issue. Both of these technicians are well qualified - I used one for many years as the exclusive tech in the Colorado / Wyoming region when I was the Kurzweil rep (2003 - 2010). I'm hoping someone can shed some light on the problem. See this video: https://www.dropbox.com/s/t49qm5o4f5...noise.MOV?dl=0 This noise is random - it appeared today after said Kurzweil was on for a number of hours with light playing. It most often appears after a few hours - the best time is about hour 3 or 4 of rehearsal when everyone is tired and my master volume is all but maxxed into our Mackie DL32R that we all use in-ear monitors with. Wakes us RIGHT up. It sounds like it's coming from the output section - maybe the DAC's? All I know is that I'd really like to use this board live and leave my PC3K8 in the studio - which is now in the road case as my main axe. Feel free to email me at ivorycj@me.com with any ideas. The right one may very well get some industry swag from me (I still rep a number of cool guy products in the industry) Thanks! CJ Link to comment Share on other sites More sharing options...
Members pdiddy Posted September 2, 2015 Members Share Posted September 2, 2015 Just a thought - you might record the output into your DAW and analyse the sound. Knowing the freq and shape of the noise might be a clue to the source of the problem. Link to comment Share on other sites More sharing options...
Members ivorycj Posted September 2, 2015 Author Members Share Posted September 2, 2015 Thanks, pdiddy - I'll check that out. I know it's pretty LF and sounds like a chainsaw / motorcycle. Link to comment Share on other sites More sharing options...
Members delaware dave Posted September 3, 2015 Members Share Posted September 3, 2015 Have you contacted Kurzweil directly on this? Support@kurzweil.com send them the video link ..... Link to comment Share on other sites More sharing options...
Members happyrat1 Posted September 5, 2015 Members Share Posted September 5, 2015 In techspeak, the problem you are experiencing is called "motorboating" and it is common enough in audio circuits. Point your tech wizard at this article on wikipedia https://en.wikipedia.org/wiki/Motorboating_%28electronics%29 And tell him to start looking for marginal caps and oscillating feedback loops. As for Swag, I'll happily accept a Kurzweil PC3K German Piano Expansion module for my trouble :D J/K... Buy me a beer the next time you're in Toronto Gary Link to comment Share on other sites More sharing options...
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