[sdiy] Understanding 80s Synth Architectures

[Paul Perry]

It was a memorable day when I wandered into a charity shop(20 years ago)
and found a mint copy of MAM! How it got there among the piles of Grisham
and romance novels I do not know. Helped me a lot.
paul perry Melbourne Australia

On Sat, 5 Feb 2022 at 09:32, Nathan Trites <nathan at idmclassics.net> wrote:

> Focusing on polysynth/polyphonic sampler architecture was how I spent my
> winter so far. To echo previous recommendations: Musical Applications of
> Microprocessors is excellent, as well as the SCI Prophet 5 service manual,
> Rhodes Chroma site and service manuals.Other SCI service manuals are good
> too.
>
> For the computer side, I don't have many specific recommendations beyond
> those, but various intro to Z80 and 86k processor sites and courses
> <https://www.cs.mcgill.ca/~cs573/fall2002/notes/lec273/lecture8/>I've
> stumbled on through searching have been helpful to get a better
> understanding of memory mapped computers in general. There is also a huge
> retro computer scene now, and some Youtube channels like Adrians Digital
> Basement, Noel's Retro Lab and similar have in-depth videos on debugging
> computer problems that can help fill in the gaps missing from synth repair
> info online. I struggled to find good resources specifically for fixing
> embedded computers from the 70s/80s that would have been targeted towards
> service techs but would love something like that.
>
> Nathan
>
> On Fri, Feb 4, 2022 at 5:22 AM ackolonges fds via Synth-diy <
> synth-diy at synth-diy.org> wrote:
>
>> Hi Everyone,
>>
>> As the local SDIYer I sometimes get asked to try and fix synths from the
>> 80s like various Rolands, Korgs, Oberheims etc. and I generally just try to
>> pinpoint the rough area of the issue and replace logic chips until the
>> issue is resolved...
>>
>> Most of these synths have a CPU connected to everything via a parallel
>> address bus and a parallel data bus, with all sorts of glue logic chips
>> doing various things. They also usually just have 1 DAC, time-domain
>> multiplexed to all of the different parameters via more logic chips.
>>
>> Obviously this is very different to the modern ways that microcontrollers
>> and DACs are used in synths, and since I wasn't around in the 80s, these
>> older architectures are very foreign to me. To aid in my troubleshooting
>> efforts, I would love to better understand the details of how these
>> architectures work, so I was wondering if anyone on here would be able to
>> point me to any resources that could explain these types of systems to me,
>> be they websites, articles, or books?
>>
>> Thanks a lot for any advice you might have.
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