[sdiy] Juno 60 woes

Jack Jackson jackdamery at hotmail.co.uk
Wed Jun 10 15:28:38 CEST 2015


Success!

So I swapped out:

4049: IC 52 + IC53
4099: IC 50
4011: IC 48 + IC49
4069: IC57
74LS42: IC58

It looks like a transient blew through all these logic chips. The bottleneck that actually stopped the CPU functioning seemed to be the 4049s.

The synth now seems to be completely working except the bias of voice 2 on the VCA out test point is way above everything else.

Thank you all for your help!
Jack

----------------------------------------
> Date: Mon, 8 Jun 2015 14:44:54 -0400
> Subject: Re: [sdiy] Juno 60 woes
> From: bachmanm50 at gmail.com
> To: jackdamery at hotmail.co.uk
>
> Jack
>
> Well,, Pin 19 does not go to the IC53 or IC58 like 17 does.. could be
> a sign... The 4049 IC also has some rather odd symbol markings on
> those upper two inverters, makes me wonder if there are some tack-ons
> there?.. maybe pop those ICs one at a time and see if your single
> starts looking better (going to ground, no "mixing" of signals)
>
> Good luck
>
> Mike
>
> On Mon, Jun 8, 2015 at 4:45 AM, Jack Jackson <jackdamery at hotmail.co.uk> wrote:
>> Hi Tom,
>>
>> Certainly it's a consideration. The board looks clean. I ran some impedance tests and didn't see anything awry. A colleague pointed out if you look at the second waveform compared to the first that it's never reaching ground, so something must be pulling it up. Also there seems to be a second waveform mixed in, so possibly the line is shorted to another at some point.
>>
>> Best,
>> Jack
>>
>>> Subject: Re: [sdiy] Juno 60 woes
>>> From: tom at electricdruid.net
>>> Date: Mon, 8 Jun 2015 00:04:59 +0100
>>> CC: synth-diy at dropmix.xs4all.nl
>>> To: jackdamery at hotmail.co.uk
>>>
>>> Is the Juno60 at all like the Poly6, where the tracks get corroded and all kinds of weird stuff happens? Dodgy address lines sounds like it.
>>>
>>> My Poly6 kept throwing all kinds of weird faults all over the place, but eventually, they were all traceable to corroded lines on one of the processor busses. Working out that everything that went faulty was on the same bus was the key thing that identified the problem. Once I'd patched some wires in across the damaged tracks, everything started to spring back to life.
>>>
>>> HTH,
>>> Tom
>>>
>>> On 7 Jun 2015, at 23:30, Jack Jackson <jackdamery at hotmail.co.uk> wrote:
>>>
>>>> Hi all,
>>>>
>>>> The CPU seems to be locking up/malfunctioning due to a dodgy address line. I think I've tracked it down to pin 17 of the CPU on the CPU board, highlighted in blue on the linked diagram. I measure this line compared to the other three address lines with my scope. The level is only 382mV (on a x10 probe) compare to 500mv of the other three lines. As you can see it connects to multiple places. Apart from just aimlessly replacing all the chips any likely areas or surefire ways to locate the problem? Cheers.
>>>>
>>>> The diagram : https://www.flickr.com/gp/131625832@N02/h25cB9
>>>> ----------------------------------------
>>>>> Date: Fri, 5 Jun 2015 15:10:03 -0700
>>>>> From: grant at musictechnologiesgroup.com
>>>>> To: synth-diy at dropmix.xs4all.nl
>>>>> Subject: Re: [sdiy] Juno 60 woes
>>>>>
>>>>> He lifted the INT pin but didn't use a pullup so those tests he did were
>>>>> useless if you ask me.
>>>>>
>>>>> On 6/5/2015 7:12 AM, Richie Burnett wrote:
>>>>>> The CPU interrupt input should most likely be predominantly high but
>>>>>> occasionally pulsing low. Probably something like every 1ms to every
>>>>>> 100ms.
>>>>>>
>>>>>> Were all the other clock frequencies correct?
>>>>>>
>>>>>> -Richie,
>>>>>>
>>>>>>
>>>>>> -----Original Message----- From: Jack Jackson
>>>>>> Sent: Friday, June 05, 2015 9:34 AM
>>>>>> To: Richie Burnett ; Sdiy
>>>>>> Subject: Re: [sdiy] Juno 60 woes
>>>>>>
>>>>>> Hi Richie,
>>>>>>
>>>>>> Thanks for your response.
>>>>>>
>>>>>> I think the interrupt is being generated (its active low and the line is
>>>>>> at ground level).
>>>>>>
>>>>>> It seems that the INT is not being cleared by the CPU. Only the top
>>>>>> octave (roughly) of keys seem to do anything. but they don't seem to
>>>>>> relate to frequency correctly, they just play a frequency.
>>>>>>
>>>>>> Cheers,
>>>>>> Jack
>>>>>>
>>>>>> ----------------------------------------
>>>>>>> From: rburnett at richieburnett.co.uk
>>>>>>> To: jackdamery at hotmail.co.uk; synth-diy at dropmix.xs4all.nl
>>>>>>> Subject: Re: [sdiy] Juno 60 woes
>>>>>>> Date: Thu, 4 Jun 2015 22:15:48 +0100
>>>>>>>
>>>>>>> On Panel Board B, Check for...
>>>>>>>
>>>>>>> 4 MHz clock signal on pin 1 of IC26 (TC40H393P),
>>>>>>>
>>>>>>> 2 MHz clock signal on pin 3 of IC26 and also pin 20 of IC24,
>>>>>>>
>>>>>>> 500 kHz clock signal on pin 5 and pin 13 of IC26,
>>>>>>>
>>>>>>> 31.25 kHz clock signal on pin 8 of IC26,
>>>>>>>
>>>>>>> Periodic low pulses on pin 4 of IC27 (TC40H002P),
>>>>>>>
>>>>>>> Also check the voltage at pin 21 of IC24 relative to ground (pin4 same
>>>>>>> chip.)
>>>>>>>
>>>>>>> See bottom left corner of PANEL BOARD B schematic in Juno 60 Service
>>>>>>> Notes.
>>>>>>> The circuit seems to mostly relate to the DCB interface, but appears
>>>>>>> to be
>>>>>>> where the main CPU board processor's interrupt signal is being generated,
>>>>>>> (or not being generated in your case.)
>>>>>>>
>>>>>>> Hope this helps. Good luck,
>>>>>>>
>>>>>>> -Richie,
>>>>>>>
>>>>>>> -----Original Message-----
>>>>>>> From: Jack Jackson
>>>>>>>
>>>>>>> OK so I tried bending up the int pin on the CPU and then inserting the
>>>>>>> chip
>>>>>>> so the INT pin is not connected. Now I appear to get a signal and some
>>>>>>> control of the parameters but only one frequency (one voice) and it
>>>>>>> stays on
>>>>>>> but I only hear this when i either press a key and then tap the INT
>>>>>>> pin with
>>>>>>> my finger, or move the bender and tap the INT pin.
>>>>>>>
>>>>>>> Any ideas?
>>>>>>>
>>>>>>
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