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Kn1000 distorted sounds

Some months ago I bought a technics kn 1000. Now happen that some sounds p.e. specially piano,brass,trumpet distort. It's a sound like blowing like Schhh mostly in the beginning of the note. Sometimes it nearly change in a ugly way to another sound . Som…

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Kn1000 distorted sounds

Joing

Joing
Spain

Total Posts: 2
Joined: September 9, 2016

Some months ago I bought a technics kn 1000. Now happen that some sounds p.e. specially piano,brass,trumpet distort. It's a sound like blowing like Schhh mostly in the beginning of the note. Sometimes it nearly change in a ugly way to another sound . Some sounds like pop organ,mallet o the bass seams not so affected. MIDI function well. Also the keyboard percussion always function well.
The problem is not always, it comes and go.
It would be great to get some help for solution this story, specially because I like this keyboard

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Posted on February 17, 2017 at 8:58 AM
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3 Replies

RMepstead

RMepstead
United Kingdom

Total Posts: 164
Joined: May 28, 2014

Re: Kn1000 distorted sounds

From what you say it sounds like a speakers vibration which is affected more by some instruments than others.

Posted on February 17, 2017 at 4:40 PM

Joing

Joing
Spain

Total Posts: 2
Joined: September 9, 2016

Re: Kn1000 distorted sounds

Thanks for your fast reply. Well sometimes it sound like a speaker problem. But I don't think that is the problem, because if I use another speaker the problem still exists. I think it's more a problem of the place where the sound is generated o in the way, well in reality I don't know what 's the matter

Posted on February 17, 2017 at 5:23 PM

davetutt

davetutt
United Kingdom

Total Posts: 166
Joined: January 12, 2015

Re: Kn1000 distorted sounds

I have had occasion to change the DAC chips on some keyboards from the Technics family. There is also an issue with the soldering on one of the VLSI chips on the outputs directly feeding the DAC's so this is a possibility. The sound you describe is something I have found before.

First thing is to check all the power lines. The key ones at the output of the DAC are the split rail 5volt supplies that centre the output of the DAC. Both these supplies must be extremely clean else there will be noise in the op-amp buffer and hence some distortion in the subsequent output.

So the main voice board has a main 5 volt supply, +-15 and from these two rails a +-5 for the DAC buffer trim circuit. The main 5volt supply originates in the switching circuit on the main power, amp board and C9 1000uf 6volt is its smoothing capacitor which is likely to need changing as it will be old. Fit a 16volt 105 degree type to extend the life of the keyboard. Other components to check with substitution are C51, C52 and C53 in the DAC buffer circuit. The only way to be sure of these power lines is to have a look at them with a scope but generally if you replace the capacitors it should bring back the sound to normality.

If you do not have the skills to do these jobs yourself please find a suitable engineer as should you attempt it and cause more damage there are no spare boards and it is unlikely to be possible to fix any subsequent damage. The main voice board is plated through two layer PCB which it is unlikely you will have the tools to extract the components without something getting broken. Don't risk it.

Hope this helps.

Dave Tutt

Posted on February 27, 2017 at 11:34 PM