Vintage Synth Repair

Hi guys,

In my Juno106 there's always an audio signal on the audio_out port 
that is faintly audible, but strong enough to the point that it's 
intorelable during a recording. In order to get rid of it I need to 
switch off the generators - DCO sawwave, DCO pulsewave, subosc - 
depending on what is employed in a given patch. But then, of course, 
I cannot play. The signal changes pitch if I press several keys. I 
mean - now I hear C1. But I just need to press several different keys 
in another octave, lets say in the last tone, and then the signal 
changes into e.g E5. Basically the note played by the synth itself is 
the last note/key I struck. 

Some guy says this: "You have a defective 80017a voice chip that 
doesn't shut off its VCA when that voice is played. You can get a 
replacement chip at www.synthparts.com". Is it really so?

I can tell you that the 106 has been on for the entire day today and 
nothing chages, this signal/voice just keeps on sounding. But does it 
mean that along with time the chip's condition is going to 
deteriorate and finally it'll start to lose the voice ?

If so, may I buy a new chip from this guy?
http://users.skynet.be/bk318113/303/juno.html
It's cheaper and new.

Of course I would neeed a service manual for Juno106.
Waiting for your help.

cheers

Have you checked all the basic things... i.e correct voltages, heated 
parts, etc ?

I once fixed a 106 which had a bad VCF/VCA chip. The bad chip heated 
as hell !


--- In vintagesynthrepair@yahoogroups.com, "sputnik979" 
<sputnik979@...> wrote:
>
> Hi guys,
> 
> In my Juno106 there's always an audio signal on the audio_out port 
> that is faintly audible, but strong enough to the point that it's 
> intorelable during a recording. In order to get rid of it I need to 
> switch off the generators - DCO sawwave, DCO pulsewave, subosc - 
> depending on what is employed in a given patch. But then, of 
course, 
> I cannot play. The signal changes pitch if I press several keys. I 
> mean - now I hear C1. But I just need to press several different 
keys 
> in another octave, lets say in the last tone, and then the signal 
> changes into e.g E5. Basically the note played by the synth itself 
is 
> the last note/key I struck. 
> 
> Some guy says this: "You have a defective 80017a voice chip that 
> doesn't shut off its VCA when that voice is played. You can get a 
> replacement chip at www.synthparts.com". Is it really so?
> 
> I can tell you that the 106 has been on for the entire day today 
and 
> nothing chages, this signal/voice just keeps on sounding. But does 
it 

> mean that along with time the chip's condition is going to 
> deteriorate and finally it'll start to lose the voice ?
> 
> If so, may I buy a new chip from this guy?
> http://users.skynet.be/bk318113/303/juno.html
> It's cheaper and new.
> 
> Of course I would neeed a service manual for Juno106.
> Waiting for your help.
> 
> cheers
>

So I understand that what you're saying is that this is indeed the 
VCA/VCF chip problem and nothing else?

PS. New info: every couple of notes the filter cutoff is slightly lower 
than the other notes I strike. But it's not every sixth note. It's more 
random.

And when in the test mode, the 1st voice (so the LCD shows) is the one 
that always gets stuck on. And here the problem manifests itself 
exactly every six notes. I guess I need to replace 80017a number one?

cheers


--- In vintagesynthrepair@yahoogroups.com, "gil_we" <gil_we@...> wrote:

>
> Have you checked all the basic things... i.e correct voltages, heated 
> parts, etc ?
> 
> I once fixed a 106 which had a bad VCF/VCA chip. The bad chip heated 
> as hell !

yes. chip one is suspect.  but see if you can pinpoint which voices
have the filter cutoff problem.  that problem is likely also
associated with the 80017's, but you may have more than just chip no.
1 to replace!  in my experience when one goes, the others aren't far
behind.  oh, and it's typically wise to wait 15-30 minutes before
doing these tests so the instrument is performing at normal operating
temperature.  you may even notice one or two of the 80017 chips are
hot to the touch.  that's not good.  good luck!



--- In vintagesynthrepair@yahoogroups.com, "sputnik979"
<sputnik979@...> wrote:

>
> So I understand that what you're saying is that this is indeed the 
> VCA/VCF chip problem and nothing else?
> 
> PS. New info: every couple of notes the filter cutoff is slightly lower 
> than the other notes I strike. But it's not every sixth note. It's more 
> random.
> 
> And when in the test mode, the 1st voice (so the LCD shows) is the one 
> that always gets stuck on. And here the problem manifests itself 
> exactly every six notes. I guess I need to replace 80017a number one?
> 
> cheers
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "gil_we" <gil_we@> wrote:
> >
> > Have you checked all the basic things... i.e correct voltages, heated 
> > parts, etc ?
> > 
> > I once fixed a 106 which had a bad VCF/VCA chip. The bad chip heated 
> > as hell !
>

I detected a bad 80017 only by heat, once. The bad chip was so hot 
that it was clear it was the cause for the problem. All voltages main 
were bad too.


--- In vintagesynthrepair@yahoogroups.com, "easterleggs" 
<milotoll@...> wrote:
>
> yes. chip one is suspect.  but see if you can pinpoint which voices
> have the filter cutoff problem.  that problem is likely also
> associated with the 80017's, but you may have more than just chip 
no.
> 1 to replace!  in my experience when one goes, the others aren't far
> behind.  oh, and it's typically wise to wait 15-30 minutes before
> doing these tests so the instrument is performing at normal 
operating
> temperature.  you may even notice one or two of the 80017 chips are
> hot to the touch.  that's not good.  good luck!
> 
> 
> 
> --- In vintagesynthrepair@yahoogroups.com, "sputnik979"
> <sputnik979@> wrote:
> >
> > So I understand that what you're saying is that this is indeed 
the 
> > VCA/VCF chip problem and nothing else?
> > 
> > PS. New info: every couple of notes the filter cutoff is slightly 
lower 
> > than the other notes I strike. But it's not every sixth note. 
It's more 
> > random.
> > 
> > And when in the test mode, the 1st voice (so the LCD shows) is 
the one 
> > that always gets stuck on. And here the problem manifests itself 
> > exactly every six notes. I guess I need to replace 80017a number 
one?
> > 
> > cheers
> > 
> > 
> > --- In vintagesynthrepair@yahoogroups.com, "gil_we" <gil_we@> 
wrote:
> > >
> > > Have you checked all the basic things... i.e correct voltages, 
heated 
> > > parts, etc ?
> > > 
> > > I once fixed a 106 which had a bad VCF/VCA chip. The bad chip 
heated 

> > > as hell !
> >
>