[sdiy] Becoming better at understanding difficult analog schematics

[Ashlyn Black]

One thing to remember is that older schematics would not have been made 
with CAD, just basic drafting tools like pencils, rulers, T-squares, 
stencils, etc. If it looks like they went back and added things in here 
and there, they probably did? They wouldn't have wanted to redraw the 
entire thing. They might have cut sections out and Xerox'd them into new 
arrangements at most. I'm guessing any grid lines on the original 
drafting paper would have been too faint for photocopiers to replicate.

Don't know for sure, I wasn't around then. I started electronics in 2015 
with a full arsenal of open-source CAD software and swathes of 
inexpensive components in standardized packages already available to me. 
The process of designing electronics now would look very very different 
to how it did in the 60's and such. Back then you'd probably design a 
thing and have to redo it multiple times due to like, supply issues or 
cost reduction or changing requirements...

Maybe someone who was there can weigh in?

- Ashlyn


On 12/5/24 15:51, Paulo Constantino via Synth-diy wrote:
> The most frustrating part for me is that I understand all the basic 
> building blocks in electronics: all types of transistor amplifiers, 
> op-amp amplifiers, oscillators, many types of filters, current 
> mirrors, differential amps and so on, but still, many schematics I 
> look at look nothing like those. They have transistors, capacitors and 
> resistor feedbacks all over the place that I cannot assign as any 
> types of amplifiers, or other building blocks that I know of. It's 
> like the designer just thought of a circuit in steps, realizing what 
> the voltages and currents are doing at a certain point and then adding 
> feedback and extra paths to those points in steps, but then the end 
> product is not easily understandable.
> I'm not sure how to describe this. It looks kinda like someone 
> building a structure using lego blocks, adding bridges from place to 
> place.
>
> On Sun, May 12, 2024 at 6:40 AM brianw <brianw at audiobanshee.com> wrote:
>
>     I studied Electrical Engineering, but I do not recall any course
>     that actually taught how to read schematics, per se. However,
>     there are some basics like Kirchhoff's Laws (current and voltage)
>     which typically test your ability to unwind a schematic, and I
>     think that understanding those laws helps decipher a schematic.
>
>     There's also a general style for schematic flow that almost
>     everyone follows. There are, of course, many slight variations on
>     that general style, but most variations are not too upsetting.
>
>     I did once work on a prototype designed by a very famous early
>     electronics era person, and the style was so out of the ordinary
>     that I could not make sense of it. In a way, this exception almost
>     proved the rule that most designers try to arrange things the same
>     way everyone else does, to improve understandability.
>
>     By the way, I spent some time reverse-engineering guitar pedals
>     from the circuit board traces. That was an interesting exercise,
>     because the arrangement of parts and traces on a board is not the
>     same as it is in the 'standard' schematic flow. I would write down
>     the schematic as it was arranged on the board, as a first draft,
>     and then rearrange the 'same' schematic in the 'standard' flow.
>     The second draft would also group things into high level blocks,
>     to make them more readable. Guitar pedals are so small that the
>     physical components cannot be separated into high level functions
>     - instead they might be tightly interwoven. That might be another
>     exercise that could help you rearrange components in your head
>     while reading schematics.
>
>     Finally, learning the basics of op-amp theory (no current in or
>     out of the inputs, at least not in the steady state, etc) might
>     help you understand feedback a little better. Of course, not all
>     circuits with feedback use op-amps, and discrete transistors
>     usually require more than basic electronics to understand, but a
>     little knowledge might go a long way.
>
>     Brian
>
>
>     On May 11, 2024, at 4:41 PM, Paulo Constantino wrote:
>     > Hi all,
>     >
>     > I wanted to ask a question that has been on my mind lately.
>     >
>     > I consider myself a beginner in electronics.
>     > I know all the fundamental stuff, or how can I express it... I
>     understand the landscape of electronics from a high point of view.
>     >
>     > However what gets me constantly is this...
>     > When I look at analog electronics schematics, specially big
>     ones, they don't make sense to me, or at least not within the
>     first few minutes of looking at them. I find that most schematics
>     are highly "non-linear". By that I mean that there are feedback
>     loops everywhere, many times from places in the schematics that
>     are far away from each other.
>     >
>     > Schematics that are more linear flowing are easier for me
>     because I can see the "blocks" and how they connect to each other.
>     But many schematics are so non-linear and I find that difficult to
>     understand.
>     >
>     > How to become better at this? If you are an experienced
>     electronics engineer, can you yourself understand these
>     "non-linear" schematics by just looking at them if you have not
>     seen that type of circuit before?
>     >
>     > Thank you very much for reading this and responding if you can.
>     >
>     > Paulo
>
>
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