Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com>
wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a >manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

A schematic is not intended to convey the information that you're
looking for. You can only intuit.

RL

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/10/23 13:36, Cursitor Doom wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

Sure! It's hard to guess what went on in the orginal designer's
mind. Usually it's something smart that I did not understand,
sometimes it's something silly that the designer did not
understand.

Often, simulating the mystery circuitry helps to clear things up.
Sometimes you have to grind the math.

Circuitry that looks superfluous may be there to deal with
special conditions, such as power-up or down, or surge protection.
It may be there to improve linearity/distortion, for temperature
compensation, or it may be a stability or bandwidth tweak. Many
other reasons are possible.

In patents or proprietary circuitry, it may be there to confuse
or mislead.

Jeroen Belleman

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 2023-12-10, John Larkin wrote:

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com>
wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a >>certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a >>manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers >>here? Just curious....

CD

Sure, I see stuff that makes no sense, especially in amateur circuits
posted online.

If I posted my schematics, I'd totally be guilty of this :D

(Although that being said, mine are very simplistic much of the time, so there's not very much to "get wrong" anyway)


--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com>
wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a >manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

Sure, I see stuff that makes no sense, especially in amateur circuits
posted online.

HP and Tek and such used to reveal schematics but don't any more, so
we seldom see professional stuff these days. Eval board schematics
don't help because they plaster them with every possible or impossible
option.

My schematics are elegant but I don't reveal the good ones. We do
sometimes include just-in-case parts, but their values are * so that's
obvious.

When you see a mystery, post a link here and we'll analyze or abuse
it.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Cursitor Doom <cd@notformail.com> wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

In my misspent youth, one of the least useless things I did was to go
through app notes, assume that all the circuits were junk, and figuring out what was wrong with them.

Lots of them were perfectly functional, but I could usually find valid criticisms. Some had lock-up states, or needed protection circuits, or used
the wrong parts just because they happened to sell them.

So it’s a pretty good way to learn about circuits.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Sun, 10 Dec 2023 07:42:04 -0800, John Larkin <jl@997PotHill.com>
wrote:

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com>
wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a >>certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a >>manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers >>here? Just curious....

CD

Sure, I see stuff that makes no sense, especially in amateur circuits
posted online.

HP and Tek and such used to reveal schematics but don't any more, so
we seldom see professional stuff these days. Eval board schematics
don't help because they plaster them with every possible or impossible >option.

My schematics are elegant but I don't reveal the good ones. We do
sometimes include just-in-case parts, but their values are * so that's >obvious.

When you see a mystery, post a link here and we'll analyze or abuse
it.

Nice to know I'm not alone! To take just the latest example of the
phenomenon, I've been working on a vintage oscilloscope which was
DOA:a Tektronix 7000 series from 1970. The PSU section was faulty.
I've got it working now, but not through understanding exactly how it
works; just old-style trouble shooting. Anyway, I was curious about
the +5V regulator section.
Here's the regulator board in its totality:
https://tinyurl.com/a3a5wmj7

And here's a close-up of the 5V section:
https://tinyurl.com/ymdbauyw

There's a pair of transistors contained within a monolithic array of
five in all. U973E and U973D and 'D' had blown and the output was
sitting at just over 11V instead of the correct level of 5V. Upon
replacing 'D', the output reverted to +5V. That was the last of the
outputs requiring attention and the PSU now works, but I still don't
understand the purpose of the 'E' and 'D' pairing.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/10/2023 7:36 AM, Cursitor Doom wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

Yes. Also I've run into some that are design flaws.
Ed

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 10/12/2023 6:56 pm, Dan Purgert wrote:

On 2023-12-10, Cursitor Doom wrote:

On Sun, 10 Dec 2023 07:42:04 -0800, John Larkin <jl@997PotHill.com>
wrote:

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com>
wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a
manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers >>>> here? Just curious....

CD

Sure, I see stuff that makes no sense, especially in amateur circuits
posted online.

HP and Tek and such used to reveal schematics but don't any more, so
we seldom see professional stuff these days. Eval board schematics
don't help because they plaster them with every possible or impossible
option.

My schematics are elegant but I don't reveal the good ones. We do
sometimes include just-in-case parts, but their values are * so that's
obvious.

When you see a mystery, post a link here and we'll analyze or abuse
it.

Nice to know I'm not alone! To take just the latest example of the
phenomenon, I've been working on a vintage oscilloscope which was
DOA:a Tektronix 7000 series from 1970. The PSU section was faulty.
I've got it working now, but not through understanding exactly how it
works; just old-style trouble shooting. Anyway, I was curious about
the +5V regulator section.
Here's the regulator board in its totality:
https://tinyurl.com/a3a5wmj7

And here's a close-up of the 5V section:
https://tinyurl.com/ymdbauyw

Shame you locked them behind whatever "yandex" is.

Those links require a login to view. But if this scope is the TEK7623A
you asked about in May 2023 then U973D and U973E form a long tail pair differential amplifier (in essence an op amp).

The 5V sense line is divided by 4kohm and 40kohm against the -50V rail
so that when in regulation the feedback voltage is zero, that is the
input to U973E base. The other half of the long tail pair U973D is doing
the comparison to zero (it's base is connected to zero volts by a resistor).

U973A and B form another diff amp for the current limit function. They
used similar structures for the -50V +50V -15V and +15V regulators.

piglet

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 2023-12-10, Cursitor Doom wrote:

On Sun, 10 Dec 2023 07:42:04 -0800, John Larkin <jl@997PotHill.com>
wrote:

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com> >>wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a >>>certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a >>>manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers >>>here? Just curious....

CD

Sure, I see stuff that makes no sense, especially in amateur circuits >>posted online.

HP and Tek and such used to reveal schematics but don't any more, so
we seldom see professional stuff these days. Eval board schematics
don't help because they plaster them with every possible or impossible >>option.

My schematics are elegant but I don't reveal the good ones. We do
sometimes include just-in-case parts, but their values are * so that's >>obvious.

When you see a mystery, post a link here and we'll analyze or abuse
it.

Nice to know I'm not alone! To take just the latest example of the phenomenon, I've been working on a vintage oscilloscope which was
DOA:a Tektronix 7000 series from 1970. The PSU section was faulty.
I've got it working now, but not through understanding exactly how it
works; just old-style trouble shooting. Anyway, I was curious about
the +5V regulator section.
Here's the regulator board in its totality:
https://tinyurl.com/a3a5wmj7

And here's a close-up of the 5V section:
https://tinyurl.com/ymdbauyw

Shame you locked them behind whatever "yandex" is.


--
|_|O|_|
|_|_|O| Github: https://github.com/dpurgert
|O|O|O| PGP: DDAB 23FB 19FA 7D85 1CC1 E067 6D65 70E5 4CE7 2860

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Sun, 10 Dec 2023 18:56:15 -0000 (UTC), Dan Purgert <dan@djph.net>
wrote:

On 2023-12-10, Cursitor Doom wrote:

On Sun, 10 Dec 2023 07:42:04 -0800, John Larkin <jl@997PotHill.com>
wrote:

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com> >>>wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a >>>>certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a >>>>manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never >>>>made any formal study of electronics. But what about our pro designers >>>>here? Just curious....

CD

Sure, I see stuff that makes no sense, especially in amateur circuits >>>posted online.

HP and Tek and such used to reveal schematics but don't any more, so
we seldom see professional stuff these days. Eval board schematics
don't help because they plaster them with every possible or impossible >>>option.

My schematics are elegant but I don't reveal the good ones. We do >>>sometimes include just-in-case parts, but their values are * so that's >>>obvious.

When you see a mystery, post a link here and we'll analyze or abuse
it.

Nice to know I'm not alone! To take just the latest example of the
phenomenon, I've been working on a vintage oscilloscope which was
DOA:a Tektronix 7000 series from 1970. The PSU section was faulty.
I've got it working now, but not through understanding exactly how it
works; just old-style trouble shooting. Anyway, I was curious about
the +5V regulator section.
Here's the regulator board in its totality:
https://tinyurl.com/a3a5wmj7

And here's a close-up of the 5V section:
https://tinyurl.com/ymdbauyw

Shame you locked them behind whatever "yandex" is.

Shouldn't be an issue. I've posted this link before a few months ago
and no one had any problem accessing it - or to be precise, no one
mentioned any issues accessing it. Perhaps the access expires after a
period. Try this:

https://disk.yandex.com/d/zkuTUiqPYczN4Q

No way does this need a password.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

Cursitor Doom <cd@notformail.com> wrote:

Here's the regulator board in its totality:
https://tinyurl.com/a3a5wmj7

And here's a close-up of the 5V section:
https://tinyurl.com/ymdbauyw

I do not like your link to some service that forces me to sign up to log in.

Use google drive and share the link with anyone. They go directly to the desired file and do not have to log in.



--
MRM

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On a sunny day (Sun, 10 Dec 2023 17:32:25 -0000 (UTC)) it happened Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote in <ul4sn9$2olha$1@dont-email.me>:

Cursitor Doom <cd@notformail.com> wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a
manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

In my misspent youth, one of the least useless things I did was to go
through app notes, assume that all the circuits were junk, and figuring out >what was wrong with them.

Lots of them were perfectly functional, but I could usually find valid >criticisms. Some had lock-up states, or needed protection circuits, or used >the wrong parts just because they happened to sell them.

So it’s a pretty good way to learn about circuits.

Repairing fast
imagine working in a TV studio, and some equipment breaks down
either while on the air or in a recording session with many artists
and a hysterical producer.
You got minutes to fix things or find some solution to work around the issue
A black screen causes a revolt in the country.

I once came back from far and needed some job to get some money to eat,
some agency send me to some TV repair shop that needed a helping hand.
I repaired the sets so fast the guy got pissed because he could not charge people more for few minutes work..
One day he brought in a defective TV set, 'fix this'
Took me 10 minutes or so, he then got so angry he took the set
and smashed it on the ground, "Now fix it again".
I left, don't know what happened to the idiot.
Found a nice interesting place to work in science the next day.
Later had my own repair shop for years.

You see a million - some extremely complex - circuits and need to: 1 understand those and: 2 know how to fix those - on the spot -.
I am a curious person, worked in all sort of electronics
from high power to military to space to medical to basic scientific research to radio and TV and more
You see what works, what designs are good, what has a tendency to fail, what not..
You see a million solutions and learn a lot about many fields
and experimenting is fun too.
Electronics is everywhere these days, and what it is used for is often as interesting as electronics itself.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On a sunny day (Sun, 10 Dec 2023 18:12:26 +0000) it happened Cursitor Doom <cd@notformail.com> wrote in <dmubni91krpumttl6n4bna76e2pspfbbbe@4ax.com>:

There's a pair of transistors contained within a monolithic array of
five in all. U973E and U973D and 'D' had blown and the output was
sitting at just over 11V instead of the correct level of 5V. Upon
replacing 'D', the output reverted to +5V. That was the last of the
outputs requiring attention and the PSU now works, but I still don't >understand the purpose of the 'E' and 'D' pairing.

ILooks like a differential amplifier,
by pairing the change in Vbe over temperature you reduce errors
caused by changes in the individual Vbe differences.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On 12/10/2023 6:54 AM, John Walliker wrote:

On Sunday 10 December 2023 at 13:18:23 UTC, legg wrote:

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <c...@notformail.com>
wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a
manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

A schematic is not intended to convey the information that you're
looking for. You can only intuit.

But, isn't that true of all such design documents? The viewer is expected
to already understand what is being presented, even if it is a "foreign" design.

Can you look at "blueprints" for a building and understand WHY each
decision was made? (why engineered lumber instead of dimensioned?)

Or, a baking recipe? (why cream of tartar AND baking soda?)

Or, a wiring diagram of a vehicle? (why separate conductors for each?)

Or, a process control loop diagram? (why was face-bypass employed/not?)

Little such documentation addresses the rationale for decisions. Even
less tie those manifestations to specific requirements in a spec.

Looking at ladder-logic doesn't tell you why the controls are the way
they are, the potential for process faults (and remedies), etc.

Software, being (typically) text based, has a leg up in that a practitioner
can choose to include much of this information, even if only informally, *alongside* the actual implementation. (Sadly, *coders* tend to be responsible for the implementation while most of the important design decisions
originate with the software engineer.)

Sometimes manufacturers include circuitry that has no function, but
which can still cause problems.

Or, the functionality may not be immediately obvious to someone with
only an external view of the device. Or, bias as to how THEY expect
it to be used.

E.g., I'm exploring ways to detect LED failures. Would you
*recognize* this to be that circuitry's purpose?

Ubiquiti make a range of WiFi access
points. One intended for educational use has some extra circuitry for simulating school bells and alarms. They left the components in place
for the ordinary version (UAP-AC-PRO). Unfortunately, one of the ceramic capacitors must have been badly specified and many units failed
because leakage in that capacitor caused the PoE negotiation thresholds
to change. I have repaired one by just removing the capacitor.

There is a cost to maintaining multiple product configurations;
especially if there are physical steps required to create one
over the other.

It's often easier to produce the same device and make those
changes at a later step in the process (when you are closer
to knowing how many of each version the market demands TODAY).

E.g., I have a "module" that includes support for audio out,
and audio/video in. In some applications, it's deployed as
a single "speaker" (driven BTL), or as a pair of "stereo"
outputs, or, as a set of line level outputs (the amplifier being
superfluous). One or two microphones may be used. And, a
fixed color (or monochrome) camera with or without PTZ and/or
Ir illuminator.

It would be foolish to predict how many of each variant I
will need at any given time. And, the savings possible
by customizing the design to each specific use are far
surpassed by the cost of producing, tracking and maintaining
those variants.

Instead, make *one* bit of hardware and let the actual I/Os
present -- and slushware -- decide what it will be, "today".

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

ehsjr <ehsjr@verizon.net> wrote:

On 12/10/2023 7:36 AM, Cursitor Doom wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a
manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

Yes. Also I've run into some that are design flaws.
Ed

+1. There are a lot of circuits designed by stringing together app notes, selected by keyword searches.

Similar to coding out of Stack Overflow.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics,
Electro-optics, Photonics, Analog Electronics

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

John Larkin <jl@997PotHill.com> wrote:

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com>
wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a
manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

Sure, I see stuff that makes no sense, especially in amateur circuits
posted online.

HP and Tek and such used to reveal schematics but don't any more, so
we seldom see professional stuff these days. Eval board schematics
don't help because they plaster them with every possible or impossible option.

My schematics are elegant but I don't reveal the good ones. We do
sometimes include just-in-case parts, but their values are * so that's obvious.

When you see a mystery, post a link here and we'll analyze or abuse
it.

We add strategically-placed 0-ohm jumpers in places that might need a bead
or anti-snivet resistor.

Otherwise, pop options are mostly power supply things or range selection.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs Principal Consultant
ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics,
Electro-optics, Photonics, Analog Electronics

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Sun, 10 Dec 2023 18:12:26 +0000, Cursitor Doom <cd@notformail.com>
wrote:

On Sun, 10 Dec 2023 07:42:04 -0800, John Larkin <jl@997PotHill.com>
wrote:

On Sun, 10 Dec 2023 12:36:41 +0000, Cursitor Doom <cd@notformail.com> >>wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a >>>certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a >>>manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers >>>here? Just curious....

CD

Sure, I see stuff that makes no sense, especially in amateur circuits >>posted online.

HP and Tek and such used to reveal schematics but don't any more, so
we seldom see professional stuff these days. Eval board schematics
don't help because they plaster them with every possible or impossible >>option.

My schematics are elegant but I don't reveal the good ones. We do
sometimes include just-in-case parts, but their values are * so that's >>obvious.

When you see a mystery, post a link here and we'll analyze or abuse
it.

Nice to know I'm not alone! To take just the latest example of the >phenomenon, I've been working on a vintage oscilloscope which was
DOA:a Tektronix 7000 series from 1970. The PSU section was faulty.
I've got it working now, but not through understanding exactly how it
works; just old-style trouble shooting. Anyway, I was curious about
the +5V regulator section.
Here's the regulator board in its totality:
https://tinyurl.com/a3a5wmj7

And here's a close-up of the 5V section:
https://tinyurl.com/ymdbauyw

There's a pair of transistors contained within a monolithic array of
five in all. U973E and U973D and 'D' had blown and the output was
sitting at just over 11V instead of the correct level of 5V. Upon
replacing 'D', the output reverted to +5V. That was the last of the
outputs requiring attention and the PSU now works, but I still don't >understand the purpose of the 'E' and 'D' pairing.

Basic diff amp. +5V is proportional to -50V rail.

RL

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)

On Mon, 11 Dec 2023 13:36:11 -0000 (UTC), Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> wrote:

ehsjr <ehsjr@verizon.net> wrote:

On 12/10/2023 7:36 AM, Cursitor Doom wrote:

Gentlemen,

Has anyone ever been baffled by the intended purpose or function of a
certain sub part of a schematic? Something that defies your attempts
to discern why it was included, notwithstanding that it was used by a
manufacturer of unquestionable repute?
I get this quite frequently, but then I'm just a hobbyist who never
made any formal study of electronics. But what about our pro designers
here? Just curious....

CD

Yes. Also I've run into some that are design flaws.
Ed

+1. There are a lot of circuits designed by stringing together app notes, >selected by keyword searches.

Well, it's very tempting as those app note fragments often do the
trick. All other things remaining the same, of course.

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)