Cyrun One - crackly volume on adjustment

Cyrus One - crackly volume on adjustment


I'm looking for a little guidance. My friend gave me his beloved Cyrus One to try and fix - the audio was fading in and out on the right channel, as well as crackling on volume changes.

I opened it up and could see that the power FET's for the right channel have been previously replaced. I tried to clean out the volume pot with contact cleaner and air. Noticed C44 was bulgy, couldn't see any others, but decided to replace (hopefully) everything in the audio stage with Nichicon MUSE ES series.

The caps finally arrived, and I finished replacing them today. Listening to it now, the audio no longer fades completely out on the right channel, so I think that was the bulgy cap. And the volume/power seems equal in both channels. The sound still crackles in the right channel, but only when the volume is adjusted.

I'm thinking, because it's only when the volume pot is adjusted, that it's just the pot. But it's hard not to rule out the replaced FET (Q40), because, well, it's not the hottest soldering job. And to be honest I don't know the theory well enough to understand if a transistor or FET could add crackles.

Would you guys agree it's likely just the volume pot? I can try replacing it next to see, my friend doesn't mind loosing the balance fader.

Much appreciated.


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You already gave a good hint with that FET :cool:

Was is that or perhaps the sophisticated technical description of 'could add crackles' ;)

99% sure to be the volume control. Depending on the type fitted you might have a difficult time finding a replacement... The pots and selector switches both cause trouble on this range, depending on use of course.

Thanks Alan I'll try replacing the pot next. Do you know if I'll have to add a resistor to keep the balance centered once the Cyrus pot is removed?
I think i used MG Chemicals 404B the first round, this time I tried Deoxit D5 - liquid gold! took care of the crackle. This amp sounds gooooooood.

Does anyone know where I might be able to find a volume knob? Perhaps someone has a broken unit in the parts graveyard?


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