[sdiy] Juno 60 woes

[Jack Jackson]

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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