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Crown K Series Problem


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#1 Recording Engineer

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Posted 30 November 2013 - 07:25 PM

Picked-up a used Crown K1 and K2 from the same seller. They both hum while signal is going through them and goes away within a few seconds after signal stops (due to the Sleep Mode circuit). Also have a Yamaha P2075 from the same seller and it's quiet as can be the entire time under the exact same conditions/tests as the K1 and K2. Tried three different power circuits, lifted grounds, etc., and still the same results every time. It's weird both the Crowns have exactly the same problem, unless it's some sort of power supply problem and both amps were subjected to the same "A/C punishment". Any thoughts? Thank you.

#2 joust

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Posted 02 December 2013 - 09:45 AM

Hello RE,

Probably, you have filter cap issues (output module); You will find broken solder connections on the cap leads. This will cause premature failure of the filter caps. If the caps have leaked or domed, I recommend the replacement of the (4) filter caps, (2 x 8200uF, 110V for each output module); Also, meticulously resolder any potentially cold solder connection on both output modules, resolder jacks and mounts on the i/p board, led components on the display board, retighten output binding posts (remove and reinstall binding posts), and verify and resolder all power connectors.
Furthermore, replace the two caps, C23 and C24 (100uF 25V), in the SMPS negative supply (-13V) section. And don't forget to adjust the ULOL (under lap/over lap) settings! :)

Hope this helps!

Alain