[sdiy] Juno 6 woes (was Juno 60 woes)

synth synthesizerdiy at gmail.com
Fri Jun 12 07:13:51 CEST 2015


Hi,
Thanks for the replies.  Yes I checked out the setup and went through  
all that I could.  I could not figure out how to read the LFOs on my  
scope.

I cannot get the "R" to work on anything.  I have cleaned up the unit  
and plugged/unplugged everything before.  Is there a certain  
connection you would suggest focusing on?  Or is there some part ID  
numbers that you could suggest looking at and testing?

Page 13 of 16 in the service notes shows slider VR12 100k to be the  
"R" and that goes to the TA75558s IC11 which I have tried swapping out  
and through R118 (39K).  From there it goes to connection 11 CPU Board  
to connection 27 Release voltage.

Since the A and D work I can assume that nothing past this point is  
the problem, correct?

Following connection 27 Release Voltage to page 9 of 16 I see it going/ 
coming from the ENV Time section.  Looks like that divides into  
sections and heads to a 22K R53 then to the IR3R01 IC Pin  4.  These  
IR3R01 ICs show to be IC26-31.

This is where I would say I am lost on the matter.  It looks like the  
ADSR is controlled by these ICs.  One IC per channel.  Where is the  
signal controlling all of these 6 ICs coming from and what would I  
look at to isolate my issue with the "R" not working and being "stuck"  
on?

Thanks again for looking at this problem with me,










On Jun 10, 2015, at 5:30 PM, Tom Wiltshire wrote:

> Jack's asked probably the first question of all. This would be my  
> question to follow up:
>
> Does the envelope work ok with the VCA, or are both the VCA and VCF  
> showing the same symptoms?
>
> The Juno 6 multiplexes control for the filter envelope, and if the  
> VCA was ok, but the VCF was not, it might suggest a failure in the  
> MPX/DMPX - 4051s, so not entirely unlikely.
> If both VCA and VCF are similarly affected, and it affects all  
> voices, that suggests that the ADSR CV generation circuitry on panel  
> board B is screwed up - That's fairly basic, and in truth I'd expect  
> that the most likely failure would be corrosion on the board  
> connector between the panel board and the main board. Apply the  
> usual treatments in this case - unplug it, scrape the connector pins  
> with a small screwdriver tip to shift any corrosion, plug it and  
> unplug it a few times, rinse and repeat as necessary until clean  
> shiny metal touches clean shiny metal again.
> However, you'll always get the odd ones where something more  
> exciting gave up. Candidates in this case might be the op-amps that  
> buffer the voltage before they go to the CPU board (1/2 of IC10, 1/2  
> of IC11, IC12), or (if they've all gone funny) the op-amp that  
> produces the reference voltage for the pots (1/2 of IC9). All  
> TA555385s. (?? Am I reading that right?)
>
> If the problem doesn't affect all voices, then you're looking at  
> specifics on the faulty voice/s, and I wouldn't expect it to be  
> exactly the same issue on multiple voices.
>
> HTH,
> Tom
>
>> From: synthesizerdiy at gmail.com
>> To: jackdamery at hotmail.co.uk
>> Subject: Re: [sdiy] Juno 60 woes
>> Date: Wed, 10 Jun 2015 12:19:14 -0500
>>
>> Since it seems you might have some intimate knowledge of the Junos at
>> this point, would you happen to know where to look for an issue with
>> the ADSR on a Juno 6? The release sliders does nothing and seems to
>> output some release regardless where the slider is positioned. The AD
>> seem to work and the S is questionable. I cannot find any position of
>> any adjustment on the Synth to get any "R" to work or show any signs
>> of life.
>>
>> The synth has been fully recapped and cleaned. I have taken a look at
>> the Juno 6 service notes.pdf and see that the slider for the "R" is
>> VR12 and the amp IC should be IC11. Swapping IC11 had no change. I
>> did however get the IC11 from UTSource.
>>
>> Would you happen to know any area to look at to resolve this problem?
>>
>> Thank you for your time,
>




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