Juno 106 Crackling

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KennaOkoye
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Juno 106 Crackling

Post by KennaOkoye » Tue Jan 03, 2012 10:30 am

When I play my juno 106 with sub osc... and play with multiple voices, I hear a static in the background like an overload... but I checked meters in logic it's not clipping. I also checked on my interface in, and it's not clipping either.. with or without sub osc it still sounds like it's overloading... Tested individual voices on startup, they are fine with no noises. When I turn off the chorus, there is no more crackling. When I turn the switch in the back WITH chorus, there is cracking :( When i turn down VCA level all the way down, cracking subsides.

What could be the problem?

Here is an audio of the problem

http://soundcloud.com/kennaokoye/overload-juno

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Re: Juno 106 Crackling

Post by cornutt » Tue Jan 03, 2012 5:57 pm

I can't listen to the audio at work, but from the description it sounds like the chorus is being overdriven. That can happen with the 106, and it usually happens when playing chords with patches where higher filter resonsance settings are used. If it's happening even at low levels, the chorus circuit may need to have its DC offset adjusted. Will post more this evening when I can get to the calibration procedure.

You wouldn't necessarily see obvious clipping in the waveform, because it happens on the input side of the chorus circuit, and subsequently going through the chorus will obscure it.
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Re: Juno 106 Crackling

Post by KennaOkoye » Tue Jan 03, 2012 8:54 pm

Thank you so much. it happens when you play the lows chords... also, will most definitely happen with the saw and square on at the same time... :( Where is my chorus stuff located inside the board?

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Re: Juno 106 Crackling

Post by cornutt » Wed Jan 04, 2012 4:23 am

I finally got a chance to listen to the audio you posted, and yeah, that definitely sounds like distortion in the chorus. The chorus circuit is on the jack board, which is mounted to the underside of the left end of the panel. You will need something that can supply a sine or triangle wave to feed into the chorus to adjust the DC offsets. You'll also need a scope. Download the service manual, which contains the calibration procedure, from here:

http://www.hinzen.de/midi/juno-106/manual/index.html

The service manual also has diagrams showing which board is where and what's on each board. And, it tells you how to use the test mode.
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Re: Juno 106 Crackling

Post by KennaOkoye » Wed Jan 04, 2012 5:19 am

Will any oscilloscope do the trick or are there any special ones, that i must use? also... How do I feeed a sine wave anywhere.... from where do I harness this lol and to where does it go LOL. please help.

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Re: Juno 106 Crackling

Post by KennaOkoye » Wed Jan 04, 2012 5:48 am

Can I use a 20 MHZ oscilloscope? Also, can I use this to tune one of my chips thats out of place? or is there ANOTHER other device that I need? the chip is fine... just not really calibrated, and I can hear it. thanks

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Re: Juno 106 Crackling

Post by Stab Frenzy » Wed Jan 04, 2012 10:15 am

Check your power supply rail voltages, it sounds to me like it could be power supply caps on their way out causing a lack of headroom in the chorus circuit.

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Re: Juno 106 Crackling

Post by madtheory » Wed Jan 04, 2012 5:52 pm

Even a 15MHz scope is good for most audio related work.

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Re: Juno 106 Crackling

Post by cornutt » Wed Jan 04, 2012 6:49 pm

Yes, pretty much any scope will do, as long as the probes are halfway decent. There's lots of threads here on choosing scopes -- do a search. I actually don't think a sine wave is necessary for the chorus offset procedure; a triangle wave would probably do as well. Just use another synth to generate it. You just want to get the signal centered around the horizontal axis.

The test point on the board will be a little metal post. To apply the signal to it, get a regular patch cable and plug one end into whatever you're using as a signal generator. Then, get some cables that have alligator clips on both ends, and clip one cable to the top of the patch cable's phone jack, and the other end to the sleeve. Take the one that's clipped to the tip and connect it to the test point. Clip the other one to any convenient ground point on the synth. You'll probably have to use the same trick to scope the output. (If you're handy with a soldering iron, you might want to make a couple of cables that have a 1/4" plug on one end and alligator clips on the other end. They came in handy for all sorts of things.

And Stab had a good point about checking the power supply. Actually, that's part of the test procedure too. So is tuning the VCF's. In fact, as long as you have the synth open, you might as well go through the whole procedure. I wrote a couple of blog posts that you should read. I'll post links to them tonight. (Can't access my blog from work.)
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Re: Juno 106 Crackling

Post by KennaOkoye » Wed Jan 04, 2012 8:02 pm

Stab Frenzy wrote:Check your power supply rail voltages, it sounds to me like it could be power supply caps on their way out causing a lack of headroom in the chorus circuit.
Dude, i am a noob. Please explain what a power supply cap is? where my power chord goes?????

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Re: Juno 106 Crackling

Post by KennaOkoye » Wed Jan 04, 2012 8:08 pm

cornutt wrote:Yes, pretty much any scope will do, as long as the probes are halfway decent. There's lots of threads here on choosing scopes -- do a search. I actually don't think a sine wave is necessary for the chorus offset procedure; a triangle wave would probably do as well. Just use another synth to generate it. You just want to get the signal centered around the horizontal axis.

The test point on the board will be a little metal post. To apply the signal to it, get a regular patch cable and plug one end into whatever you're using as a signal generator. Then, get some cables that have alligator clips on both ends, and clip one cable to the top of the patch cable's phone jack, and the other end to the sleeve. Take the one that's clipped to the tip and connect it to the test point. Clip the other one to any convenient ground point on the synth. You'll probably have to use the same trick to scope the output. (If you're handy with a soldering iron, you might want to make a couple of cables that have a 1/4" plug on one end and alligator clips on the other end. They came in handy for all sorts of things.

And Stab had a good point about checking the power supply. Actually, that's part of the test procedure too. So is tuning the VCF's. In fact, as long as you have the synth open, you might as well go through the whole procedure. I wrote a couple of blog posts that you should read. I'll post links to them tonight. (Can't access my blog from work.)
Cornutt alot of jargon in there with the cables. Sorry mate... So I take a 1/4 inch cable plug it into the output of my D50 create a tri wave with it, and take that 1/4 inch put an alligator clip on it??? confused. also, I know that Chorus 1 and Chorus 2 are VR2 and VR3... is that the test point you speak of?

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Re: Juno 106 Crackling

Post by KennaOkoye » Wed Jan 04, 2012 9:50 pm

it looks like VCF WIDTH and FREQUENCY... all u need is a TUNER, not a Oscilloscope :D

I am a little confused... so I downloaded a Service manual.

Here are a list of things I seem to need. my ears, voltmeter, another synthesizer and Oscilloscope.

Connections: from the oscilloscope, what chord would I need to connect to the test points? I assyme a probe, but are all probes outfitted with what needs to connect to my Synths Test point. From my D50, from where and to, and am I connecting the synths? and With what? ( you explained that in the thread, but there are some words that I don't understand, like "sleeves." My juno 106 is an HS 60, so my module board is loacated UNDER the keys FYI. Thank you very much for your help!!!!

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Re: Juno 106 Crackling

Post by madtheory » Wed Jan 04, 2012 10:13 pm

OK. The inside of a Juno is probably not the place to learn basic electronics. Try a book, or a local school? Or take it to a tech.

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Re: Juno 106 Crackling

Post by themilford » Wed Jan 04, 2012 10:16 pm

I use the Simple Sine app on my iPhone to generate signals for simple stuff like this. Works great.

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Re: Juno 106 Crackling

Post by KennaOkoye » Wed Jan 04, 2012 10:30 pm

themilford wrote:I use the Simple Sine app on my iPhone to generate signals for simple stuff like this. Works great.
I am not taking this board anywhere. I must do it now lol

Okay, I can generate a sine wav. but then wat!? lol... how does that sine wave connect or is fed to TP2.. and to be exact it says I need the sine wav at 10v p-p 1khz

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