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Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 4:56 am
by CuBulo
I just bought a Juno-106 from a guy on VSE for $500. He said it was in great condition with all of the voice chips working which is true. All six voices are playable. But I am having one problem. When on poly 1 mode there are some notes that are bit quieter than the rest. Each quiet note is 6 notes away from each other, and the every once in a while the placement of the quiet note changes, while still being 6 notes from the next. When in poly 2 mode there are quiet notes but they are randomly grouped together and change every few seconds. There are no quiet notes when in unison mode. Please help me.

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 3:19 pm
by Synthaholic
Sounds like your Juno needs to be calibrated.

The service manual can be downloaded from here: http://manuals.fdiskc.com/flat/Roland%2 ... Manual.pdf

You'll need an oscilloscope, DVM and frequency counter or tuner to do the job properly. But as a quick fix, you could do the VCA Gain adjustment on page 19 of the service manual by ear. That should take care of the voices being unequal levels.

Turn on the Juno while holding down the KEY TRANSPOSE button. This will enter Test mode. Then press POLY 1 & 2 simultaneously so both are lit; this will cause the synth to rotate between the voices while playing and show which voice is playing on the LED. Strike a note repeatedly and note which voice is the one that is too quiet.

Then look on the module board for trimmers as follows:

Voice 1: VR27
Voice 2: VR22
Voice 3: VR17
Voice 4: VR12
Voice 5: VR7
Voice 6: VR2

Adjust the trimmer for the affected voice to bring it to the same level as the other voices.

That should get you up and running until you can either get the synth to a tech for a full calibration or acquire the gear to do it yourself.

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 5:47 pm
by CuBulo
Thank you so much :D im glad I don't have to pay for a new voice chip

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 8:46 pm
by CuBulo
WE TRIED THE TRIMMER AND IT IS DEFINITELY VOICE 1, VR27-GAIN, BUT EVEN BROUGHT UP ALL THE WAY IT IS MUCH LOWER THAT THE OTHER 5 VOICES. I DO NOT THINK IT IS RESONANCE OR ANY OF THE OTHER SETTINGS. ANY OTHER SUGGESTIONS? COULD THE GAIN BE LOW AND THE CHIP STILL WORKS OK? I PRESUMED THAT THE CHIP EITHER WORKS OR IT IS BROKEN SO THERE IS NO SOUND AT ALL. THANKS.

edit: caps was on :-/

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 8:48 pm
by Steve Jones
A quiet voice can be a VCA or a VCF issue... If you push up the resonance and pull down the cutoff to get a peaked filter sound, does the voice in question still sound softer, or does it have a different tone as well?

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 9:01 pm
by CuBulo
Yes it is a different tone as well.

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 9:25 pm
by Synthaholic
You'll need to calibrate the filter on that voice then.

If the pitch of the tone is off compared to the other voices with resonance all the way up, adjust it with VR29 (voice 1).

If the resonance is weaker on that voice compared to the other voices, adjust that with VR26.

After calibrating resonance, recalibrate the VCA level on that voice.

Where are you located? If in the northeast USA, I could calibrate it for you.

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 9:37 pm
by CuBulo
Im in Louisiana

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 11:44 pm
by CuBulo
I have done all you said and nothing has worked. Im starting to think it may just be a bad voice chip that needs replacing.

Re: Juno-106 problem (not voice chip)

Posted: Sun Dec 27, 2009 11:57 pm
by Steve Jones
CuBulo wrote:I have done all you said and nothing has worked. Im starting to think it may just be a bad voice chip that needs replacing.
Sounds like a VCF/VCA chip failing.

Re: Juno-106 problem (not voice chip)

Posted: Mon Dec 28, 2009 12:07 am
by CuBulo
The VCF is working fine, the VCA seems also not to be the problem. And why would the VCA or VCF have a problem with only one voice?

Re: Juno-106 problem (not voice chip)

Posted: Mon Dec 28, 2009 12:21 am
by Steve Jones
What you are calling a "voice chip" is a Roland module that contains the VCF and VCA for that particular voice. It is not a voice chip as such, it is not even a chip, rather it is an encapsulated sub-board with some chips and caps and some surface mount resistors on it. Roland called it an 80017A. They have always had a high failure rate, and they have several failure modes, including the one that you have described. There is one for each voice, so a failing module will only effect that particular voice.

Re: Juno-106 problem (not voice chip)

Posted: Mon Dec 28, 2009 1:10 am
by CuBulo
So replacing the voice chip would fix the problem correct?

Re: Juno-106 problem (not voice chip)

Posted: Mon Dec 28, 2009 1:34 am
by Maschinengeist
I should check in my boxes but I think I've got a 80017a left.

Re: Juno-106 problem (not voice chip)

Posted: Mon Dec 28, 2009 2:40 am
by CuBulo
Where can I buy a replacement?