What's Wrong With My Juno-106?

[Mooger5]

In a well calibrated polysynth each voice will sound as identical to the next one as possible. In Poly Mode 1 when you hit a note repeatedely, the Juno will scroll through the voices, one at a time. Each voice has its own filter and with high resonance settings you can notice if they are in tune or not. Seems to be the case with three of your synth´s voices. Did it have voice chips replaced?

That scope is fine, but if you don´t seem to even know what the multimeter is for, you better spend your money on neither. Pay a tech. Sorry, can´t be assertive here without sounding like a total a*s. The truth is I don´t know how you could teach someone who can´t read how to play scrabble... Plus there are lethal voltages inside the synth!

DCOs don´t go out of tune, but the master tuning might be slightly sharp or flat. There´s a tuning pot next to the output jacks.

[Lester Drek]

The voice chips have their coating removed so I think they were just serviced in the past. I bought this off CL so I'm not sure of its service history. I think I saw a service sticker that said 1999 maybe.

I want to do the repair myself. I'm a young guy and I want to learn more about this stuff. The internet and youtube is my best friend . I was watching the videos on how to use the multimeter and oscilloscope. The master tuning isn't out of place. I think just the Saw DCO is out of tune, is that possible?

So since voices 4-6 sound completely out of tune with the res up AND already have the coating removed, should I replace them? Or will using the multimeter and oscilloscope fix this issue?

[madtheory]

Learning is great. But don't do it on a synth that's worth around $1000. Start with some shitty guitar pedals first. Something that won't cost $$ if you break it.

[Mooger5]

That´s good advice madtheory. Lots of pedal kits out there and a million stripboard layouts! They are great for learning the basics. From component selection to the art of soldering. And troubleshooting. First builds always go wrong!

IMO Welleman offer the best kits for beginners. The instructions are so clear, they´re a step by step guide on how to build anything, really.

[Mooger5]

The voice chips have they're coating removed so I think they were just serviced in the past. I bought this off CL so I'm not sure of its service history. I think I saw a service sticker that said 1999 maybe.

OK, it´s possible the chips were´nt soldered to the voice board in the same order as they were before. Due to component tolerances the calibration for one chip won´t be the same for another.

I want to do the repair myself. I'm a young guy and I want to learn more about this stuff. The internet and youtube is my best friend . I was watching the videos on how to use the multimeter and oscilloscope. The master tuning isn't out of place. I think just the Saw DCO is out of tune, is that possible?

That´s the spirit. Glad you took my previous reply well. Hate to sound so arrogant but sometimes it´s necessary.
The internet is the greatest source of information (and disinformation) ever. I´m hooked since ´94. Before that I had to borrow old Elektor magazines if I wanted to learn anything decent about audio electronics.

There is only one DCO per voice, outputting the multiple waveforms. No part of the DCOs goes out of tune, just the master tuner can be slightly off. It´s the VCFs that can go out of tune, when the resonance is at maximum.

So since voices 4-6 sound completely out of tune with the res up AND already have the coating removed, should I replace them? Or will using the multimeter and oscilloscope fix this issue?

You don´t need to replace the voice chips yet. I´ve a hunch they just need to be calibrated. A digital multimeter is cheap these days. An analog synth is voltage controlled. Wrong voltage across components means improper control, thus improper sound. You need the multimeter to among other things read how the voltages change s while you adjust the trimmers in the voice board, until the values are closer to what the manufacturer recommends in the Servce Manual.

The oscilloscope is to, among other things, visualize the waveforms, if they distort, or if all are at the same volume. Before I had a scope I connected the output of the synth to the audio card of the pc, and used a free software, called Zelscope. Just to see how the waveforms behaved. It was useful and fun.

Cheers.

[Lester Drek]

Thanks so much for all this info guys. I bought the oscilloscope. Even if I won't use it I'll be going to college to major in music technology with a concentration in electrical and computer engineering so it will definitely come in handy.

I ordered the multimeter. I will definitely practice soldering and use the gear on some other electronics before taking a crack at the Juno.

I will get back to you guys with updates!

[Lester Drek]

That´s good advice madtheory. Lots of pedal kits out there and a million stripboard layouts! They are great for learning the basics. From component selection to the art of soldering. And troubleshooting. First builds always go wrong!

IMO Welleman offer the best kits for beginners. The instructions are so clear, they´re a step by step guide on how to build anything, really.

Wow, this sounds really cool. I'm gonna start doing that, thanks!

[Lester Drek]

The voice chips have they're coating removed so I think they were just serviced in the past. I bought this off CL so I'm not sure of its service history. I think I saw a service sticker that said 1999 maybe.

The oscilloscope is to, among other things, visualize the waveforms, if they distort, or if all are at the same volume. Before I had a scope I connected the output of the synth to the audio card of the pc, and used a free software, called Zelscope. Just to see how the waveforms behaved. It was useful and fun.

Can I use the oscilloscope to correct the volume issue or does it only show me the volumes? I do have some patches that are much lower than others, even when adjusting all the parameters.

[jxalex]

Just don't. Especially if You do not know what is "short circuit".

See You after 2 years of self-learning the basics.

[Lester Drek]

Just don't. Especially if You do not know what is "short circuit".

See You after 2 years of self-learning the basics.

Thank you for the motivation to prove you wrong.

[Mooger5]

Can I use the oscilloscope to correct the volume issue or does it only show me the volumes? I do have some patches that are much lower than others, even when adjusting all the parameters.

A patch that uses say only one waveform and a very low cutoff point might sound tamer than most. There´s a slider for the final VCA in the control panel which can be memorized. The normal value is 0.

The individual VCAs in the voice chips will also have to be calibrated so all the six voices sound even. The scope will let you see the amplitude of each voice so you can then adjust the respective trimmers in the voice board accordingly.

[jxalex]

Just don't. Especially if You do not know what is "short circuit".

See You after 2 years of self-learning the basics.

Thank you for the motivation to prove you wrong.

You really should listen what MadTheory told to You and begin with something simple at first and have PATIENCE. Dont do it yourself right now. You may be lucky, but also there is high possibility of screwing up with random short circuit by measurement or adjusting!

Also, do NOT rely on the youtube videos thinking that this is all You need to fix the item, while You do not grasp even the elementary about electronics. It is very easy to screw up a very delicate instrument by just a random short circuit while measuring or adjusting (and lets not talk about soldering even!).

You must learn A and B about electronics at first, also fix something simpler.

[madtheory]

You really should listen what MadTheory told to You and begin with something simple at first and have PATIENCE. Dont do it yourself right now. You may be lucky, but also there is high possibility of screwing up with random short circuit by measurement or adjusting!

Dude, relax. Turn down the drama a few notches. The guy did listen:

I will definitely practice soldering and use the gear on some other electronics before taking a crack at the Juno.

[jxalex]

I hope You are right Madtheory. Just one particular line got me to jump, becouse it indicates, possibly, the kid could not stay away from tweaking inside...

Can I use the oscilloscope to correct the volume issue or does it only show me the volumes? I do have some patches that are much lower than others, even when adjusting all the parameters.

Whatever that "adjusting all the parameters" means, and with oscilloscope besides... Lets hope it was just limited to faders on the synth front panel only and not inside the synth.

[madtheory]

It's not about whether I am right or wrong, it's what the guy said- he'll practice on other stuff before taking a crack at the Juno. That service manual is one of the clearest ever written. You can calibrate the machine with just the basics, and it doesn't require soldering.