[sdiy] Help with Jupiter 8 clone

[rburnett at richieburnett.co.uk]

The "Hi-Fi special" diodes look like they are just there to prevent the 
power supply rails from reversing polarity if something else were to 
fail.  As such they are protection devices and would be reverse-biased 
in normal operation anyway.

-Richie,


On 2022-08-01 21:59, Luís Marka via Synth-diy wrote:
> Just for the record, there is a second scan of the service manual
> around (file here:
> https://synfo.nl/servicemanuals/Roland/JP-8_SERVICE_NOTES_2nd.pdf),
> much more readable, especially component values in the crammed voice
> card section.
> 
> Anyway, it looks like the 1N5404G is the same thing. Hope the
> electrons feel at home and comfortable inside this non-hi-fi-special
> diode!
> 
> Thanks!
> 
> Em 2022-08-01 4:05 p.m., info synthcube.com escreveu:
>> At the risk of getting flamed (again) those special diodes are likely 
>> similar to other components of that era that were specially formulated 
>> to help keep electrons generally happy in their role serving as audio 
>> ambassadors and were formulated in order to accomplish those (long 
>> since lost) magic arts of electron-shaping and routing for optimal 
>> audio outcomes.
>> 
>> -----Original Message-----
>> From: Synth-diy <synth-diy-bounces at synth-diy.org> On Behalf Of John 
>> Speth via Synth-diy
>> Sent: Monday, August 1, 2022 2:25 PM
>> To: synth-diy at synth-diy.org
>> Subject: Re: [sdiy] Help with Jupiter 8 clone
>> 
>> For reference, the JP8 schematic is here:
>> http://www.synthfool.com/docs/Roland/Roland_Jupiter8/roland_jp8_service_manual.pdf
>> 
>> The Hi Fi Special diodes are probably what Roland and others might 
>> have called them in the 80s. From the schematic, the only function I 
>> can think that they could possibly perform is over-voltage shunting. 
>> Metal Oxide Varistors (MOVs) perform that same function in modern 
>> circuits. I think those diodes are the 80s version of MOVs. A modern 
>> day PS might serve you better than trying to clone an ancient design.
>> 
>> JJS
>> 
>> On 8/1/2022 10:57 AM, Luís Marka via Synth-diy wrote:
>>> Hi guys,
>>> 
>>> I am giving a serious thought about building a Jupiter 8 clone, and
>>> started to take a deeper look at the schematics (actually I already
>>> ordered some of the parts, so it looks like I will get it done
>>> eventually). In the PSU there are three GP-30G diodes tied at the 
>>> -15,
>>> +15 and +5V outputs, listed as "Hi-Fi Special" both in the schematics
>>> and in the parts list. I never heard anything about a "hi-fi special"
>>> diode, any idea what that means??
>>> 
>>> Cheers!
>>> 
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>> 
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