Author Topic: When you follow the schematic but it doesn't work  (Read 3425 times)

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Offline lordvader88

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When you follow the schematic but it doesn't work
« on: July 25, 2018, 09:12:41 am »
I'm reminded of 2-3 times I tried to make a C-R oscillator w/ a BJT and maybe an op-amp once, and they never worked. I didn't try changing much, but it never worked. I bet the schematics were fine tho.

Then 1 utuber, an old radio guy, with proper schematics from an old book, I tried 2-3 little circuits and they never worked but his did. With those it was probably the BJT or JFET not being quite right, and not getting the loop gain right.



Don't you hate it tho when you follow a schematic and it doesn't work and you don't know why ? (time to re-try some)
 

Online bd139

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Re: When you follow the schematic but it doesn't work
« Reply #1 on: July 25, 2018, 09:22:22 am »
yes very annoying. This is what got me interested in the design side of electronics if I'm honest.

I built some stuff from Practical Wireless magazine in the early 1980s that didn't work. I learned pretty quickly that a lot of the designs out there are total shite and nothing is trustworthy. The design may have worked for one person once. In some cases, I don't think the design ever worked even if the author said it did and in other cases it was actually misprinted and you'd find out two months later in a footnote on a page after you had recycled the thing for parts anyway.

Putting effort into learning why things don't work and actually looking at a design and going "huh?" has been a valuable set of lessons though.

To note, a lot of stuff we were taught at university didn't work either!

Finding stuff that should work but doesn't and making it work again is the best analytical training you can get I think.
 
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Offline lordvader88

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Re: When you follow the schematic but it doesn't work
« Reply #2 on: July 25, 2018, 09:32:11 am »
Quote
To note, a lot of stuff we were taught at university didn't work either!
You mean schematics out of text books ?
 

Online bd139

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Re: When you follow the schematic but it doesn't work
« Reply #3 on: July 25, 2018, 09:33:03 am »
Yes out of textbooks and as advised by the lecturers. It's almost as if they'd never built the things  :palm:
 

Offline blueskull

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Re: When you follow the schematic but it doesn't work
« Reply #4 on: July 25, 2018, 09:54:20 am »
Yes out of textbooks and as advised by the lecturers. It's almost as if they'd never built the things  :palm:

You will be surprised how many university professors have absolutely no idea on fields that he/she is not exactly working on (we are ARWU ECE subject ranked top 10 worldwide).

I once had a professor, teaching communication protocols, who has no idea what's differential signal and how it increases bandwidth. She only knows RS485 is faster than RS232, but has no idea why.

And I also had a professor, despite living in US for 2 decades, has no idea about American slang and English memes. She likes to eat salmon, and every time she pronounces like she likes to eat semen. And she always says she likes to "blow", of course it's something else.

Actually in our department, it's hard to find a computer engineering/network engineering professor who can read schematics, and a few EE professors who can code properly (not just grabbing crap from CodeProject or Arduino forum).

And I kid you not, we have DSP topic PhD students working on the latest imaging processing technology that has no idea how to compute a 2N point real FFT with an N point complex FFT.

Again, we have power electronics major PhD students who absolutely master control theory, but has no idea how to actually drive a MOSFET or how to design a current shunt amplifier.

And yes, we do have people who don't know ground clips are always tied together, as we did have expensive firework shows. And we do have people who can't f*ing solder.

Welcome to 2018, where everyone knows nothing at all about fields outside his/her exact field.
 
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Online GeorgeOfTheJungle

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Re: When you follow the schematic but it doesn't work
« Reply #5 on: July 25, 2018, 10:21:55 am »
We're well into the internet era, and a few years back many unis still didn't teach javascript, students can't even tell apart JS from the DOM, write async code, and barely know what's a closure if at all. If at least C were mandatory curriculum you could be assured they know well what's going on under the hood. But no. Java has been/was mandatory instead. Is it still? (IDK). On the plus side, it's no more any longer everything Windows, all Windows and no more than Windows.
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Offline HB9EVI

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Re: When you follow the schematic but it doesn't work
« Reply #6 on: July 25, 2018, 10:32:01 am »
Coming from the IT domain on college level, I'm still wondering about the classic dual system apprenticeship in IT here in CH. Those guys spend 4 years education, normally 3,5 to 4 days per week in an IT company and the rest in business school. You might think, they learn some bloody basics about IT like simple transistor circuits, flipflops,, Ohms law or logics or even the essentials about how a cpu is working:

Just forget it!

There are no essentials, no basics taught anymore nowadays. It just counts, that they know to maintain a windows installation or maybe set up PC from the basic components - but how the components actually work - no way.
they know every detail about the main tasks their companys are in; about webdesign, programming, troubleshooting some particular software or whatsoever - but as soon as they're out of their well known playground, they are lost. It's a shame
 

Online bd139

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Re: When you follow the schematic but it doesn't work
« Reply #7 on: July 25, 2018, 10:40:48 am »
Yes out of textbooks and as advised by the lecturers. It's almost as if they'd never built the things  :palm:

You will be surprised how many university professors have absolutely no idea on fields that he/she is not exactly working on (we are ARWU ECE subject ranked top 10 worldwide).

I once had a professor, teaching communication protocols, who has no idea what's differential signal and how it increases bandwidth. She only knows RS485 is faster than RS232, but has no idea why.

And I also had a professor, despite living in US for 2 decades, has no idea about American slang and English memes. She likes to eat salmon, and every time she pronounces like she likes to eat semen. And she always says she likes to "blow", of course it's something else.

Actually in our department, it's hard to find a computer engineering/network engineering professor who can read schematics, and a few EE professors who can code properly (not just grabbing crap from CodeProject or Arduino forum).

And I kid you not, we have DSP topic PhD students working on the latest imaging processing technology that has no idea how to compute a 2N point real FFT with an N point complex FFT.

Again, we have power electronics major PhD students who absolutely master control theory, but has no idea how to actually drive a MOSFET or how to design a current shunt amplifier.

And yes, we do have people who don't know ground clips are always tied together, as we did have expensive firework shows. And we do have people who can't f*ing solder.

Welcome to 2018, where everyone knows nothing at all about fields outside his/her exact field.

That was exactly my educational experience 25 years ago. Sucks doesn't it?

We're well into the internet era, and a few years back many unis still didn't teach javascript, students can't even tell apart JS from the DOM, write async code, and barely know what's a closure if at all. If at least C were mandatory curriculum you could be assured they know well what's going on under the hood. But no. Java has been/was mandatory instead. Is it still? (IDK). On the plus side, it's no more any longer everything Windows, all Windows and no more than Windows.

They're teaching C# and nodejs at my local college and their staff have absolutely no fucking idea what they are doing. We have had a couple of their "graduates" in on trial and we're basically having to get them to unlearn a lot of stuff. I mean you don't write an OO program entirely in static methods ffs. But that's what they told us. Seriously, no.
 

Offline Dubbie

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When you follow the schematic but it doesn't work
« Reply #8 on: July 25, 2018, 10:45:02 am »
I think it is a bit of a stretch to expect someone in IT to know much about electronics. They are usually working at least 5 or 6 levels of abstraction above voltages and transistors. You can’t learn everything.
 

Offline Rerouter

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Re: When you follow the schematic but it doesn't work
« Reply #9 on: July 25, 2018, 10:56:07 am »
Trade schools cover more of this stuff, but most without prior knowledge are not given enough to fill the gaps, and have it click, meaning they know some keywords, but no idea how to apply it,

I was in a high level class discussing how to measure current and voltage in an industrial setting, and that it was difficult and expensive to interface to computer control systems... yeah I had a double take. Equally things like Wheatstone bridges drawn with inductors, and other non valid symbols.

I actually completed 2/3 rds of my 4 year course in 1 week, by demonstrating my understanding of the concepts by ripping in to a pile of stuff they had sitting around for repair for the past 5 years, (it meant I only had to pay 1 semester, so I wasn't too fussed on payment) Oh you want me to show ohms law at work... well this fuse has 25V across it, so its resistance must be high..  |O

Though the fun came from what form of programming they had on hand, they had very old gamepad programmed PLC's that used ladder logic, where I would solve the problem then reduce it down to the smallest possible solution. made anyone in the class copying my work stand out like a sore thumb. and resulting in test scores along the lines of "100%, It works, but hell if I know how?"

Back to the original topic, online schematics had me throw away a lot of money early on, It takes a while to build up enough Google-Fu to know when someone is talking about something they understand. and there is a stupid amount of simple circuit images out there that plain and simply will never work without the understanding of the weird quirk they used.

 

Online rsjsouza

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Re: When you follow the schematic but it doesn't work
« Reply #10 on: July 25, 2018, 11:20:07 am »
To the OP: the schematic diagram only tells part of the story, as it does not account for the influence the physical aspects have in a proper operation. In low frequency and low noise circuits (audio, sensors, etc.) this translates in poor signal to noise ratio, while in high frequency systems (RF, high speed switching power supplies, etc.) the interconnections become components themselves. Back in the day that was one of the great difficulties we had to build circuits straight from a reference such as John Markus' Guidebook of Electronic Circuits.

To top it off, I have a similar experience as BD139: many circuits in magazines seemed to be not thoroughly tested probably due to excessive reliance on a BJT or JFET's intrinsic parameters that greatly vary in a production run. I lost count of how many circuits were put aside and how many PCBs were thrown in the trash after trying to figure out why that radio or transmitter did not work or that audio mixer or pre-amp was so damn noisy. The losses were not as dramatical when I assembled them in screw terminal bars or (at a later time) in protoboards, but when soldered terminal bars or complete PCBs were used... (components were expensive at that time).

Obviously that, over the years, I learned a thing or two as of why these things didn't work, but it takes time and a lot of reading.
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Offline Alex Nikitin

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Re: When you follow the schematic but it doesn't work
« Reply #11 on: July 25, 2018, 11:41:38 am »
As far as I remember (and I've started to be interested in electronics when I was about 14) I've never built a circuit without understanding first how it works. I don't remember ever trying to build something from a circuit in a book or in a magazine without a thorough analysis which did always end up with me building my own circuits around somebody else's ideas. I've started with a simple multimeter and a soldering iron, several books on electronic devices (mostly data sheets for valves, transistors, resistors, capacitors and so on) and gradually built my own lab - a power supply, an oscilloscope, a function generator, an AC millivoltmeter - by the time I was 18.

I see no fun whatsoever in trying to build something you don't understand  :palm: .

Cheers

Alex
 
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Online TK

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Re: When you follow the schematic but it doesn't work
« Reply #12 on: July 25, 2018, 11:54:36 am »
Yes out of textbooks and as advised by the lecturers. It's almost as if they'd never built the things  :palm:

You will be surprised how many university professors have absolutely no idea on fields that he/she is not exactly working on (we are ARWU ECE subject ranked top 10 worldwide).

I once had a professor, teaching communication protocols, who has no idea what's differential signal and how it increases bandwidth. She only knows RS485 is faster than RS232, but has no idea why.

And I also had a professor, despite living in US for 2 decades, has no idea about American slang and English memes. She likes to eat salmon, and every time she pronounces like she likes to eat semen. And she always says she likes to "blow", of course it's something else.

Actually in our department, it's hard to find a computer engineering/network engineering professor who can read schematics, and a few EE professors who can code properly (not just grabbing crap from CodeProject or Arduino forum).

And I kid you not, we have DSP topic PhD students working on the latest imaging processing technology that has no idea how to compute a 2N point real FFT with an N point complex FFT.

Again, we have power electronics major PhD students who absolutely master control theory, but has no idea how to actually drive a MOSFET or how to design a current shunt amplifier.

And yes, we do have people who don't know ground clips are always tied together, as we did have expensive firework shows. And we do have people who can't f*ing solder.

Welcome to 2018, where everyone knows nothing at all about fields outside his/her exact field.
You are quoting one extreme of the spectrum.  I am sure there are some amazing professors on the other extreme and a bunch of average in between.  Look for the world changing extreme, not the mediocre one.
 

Offline b_force

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Re: When you follow the schematic but it doesn't work
« Reply #13 on: July 25, 2018, 11:55:49 am »
As far as I remember (and I've started to be interested in electronics when I was about 14) I've never built a circuit without understanding first how it works. I don't remember ever trying to build something from a circuit in a book or in a magazine without a thorough analysis which did always end up with me building my own circuits around somebody else's ideas. I've started with a simple multimeter and a soldering iron, several books on electronic devices (mostly data sheets for valves, transistors, resistors, capacitors and so on) and gradually built my own lab - a power supply, an oscilloscope, a function generator, an AC millivoltmeter - by the time I was 18.

I see no fun whatsoever in trying to build something you don't understand  :palm: .

Cheers

Alex
Lol, that's a very interesting thought.
It really depends how someones brain works.
Some people prefer understanding every single little fart before they start.
Other people learn as they go.
(and some people can't be really bothered)

Neither of the two is good or wrong and it both has its pitfalls.
"If you can't explain it simply (or at all), you don't understand it well enough." A. Einstein

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Offline Richard Crowley

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Re: When you follow the schematic but it doesn't work
« Reply #14 on: July 25, 2018, 11:58:17 am »
One of my favorite corollaries of Murphy's Law is:

"Amplifiers will oscillate.  Oscillators won't."

I have experienced this myself on several occasions.   :palm:

And of course there is the old observation of the professors high up in their ivory towers who don't know which end of a soldering iron to hold.
« Last Edit: July 25, 2018, 12:00:21 pm by Richard Crowley »
 
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Offline b_force

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Re: When you follow the schematic but it doesn't work
« Reply #15 on: July 25, 2018, 12:03:52 pm »
Yes out of textbooks and as advised by the lecturers. It's almost as if they'd never built the things  :palm:

You will be surprised how many university professors have absolutely no idea on fields that he/she is not exactly working on (we are ARWU ECE subject ranked top 10 worldwide).

I once had a professor, teaching communication protocols, who has no idea what's differential signal and how it increases bandwidth. She only knows RS485 is faster than RS232, but has no idea why.

And I also had a professor, despite living in US for 2 decades, has no idea about American slang and English memes. She likes to eat salmon, and every time she pronounces like she likes to eat semen. And she always says she likes to "blow", of course it's something else.

Actually in our department, it's hard to find a computer engineering/network engineering professor who can read schematics, and a few EE professors who can code properly (not just grabbing crap from CodeProject or Arduino forum).

And I kid you not, we have DSP topic PhD students working on the latest imaging processing technology that has no idea how to compute a 2N point real FFT with an N point complex FFT.

Again, we have power electronics major PhD students who absolutely master control theory, but has no idea how to actually drive a MOSFET or how to design a current shunt amplifier.

And yes, we do have people who don't know ground clips are always tied together, as we did have expensive firework shows. And we do have people who can't f*ing solder.

Welcome to 2018, where everyone knows nothing at all about fields outside his/her exact field.
Can I vote you for president for almost every single school or university in the world?

When I was working for a company this drove us absolutely nuts.
Getting students or interns who can actually DO and KNOW something.
My boss at the time put it very well, "They train people to be very good and efficient in learning and making exams, not in broadening their views and understand the world around them"

What makes this story a little ironic and difficult is that there are quite some companies out there still judging someone by his level of graduation.
So even people who have an impressive CV are just being ignored when not having a certain formal level criteria.
Talking about wasting talent........

 
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Online Kleinstein

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Re: When you follow the schematic but it doesn't work
« Reply #16 on: July 25, 2018, 12:23:10 pm »
Even with a relatively simple circuit things can get wrong, by having a wrong part or wrong polarity or just broken parts. Also misprints in circuit diagrams are rather common. From memory the Elektror journal had about 2-3 corrections to older circuits per issue.

High frequency circuits are especially tricky. However also simple looking circuit not meant to oscillate can do that if murphy helps with the layout. Modern transistors are quite fast and thus one may not even see it oscillate with a slow 20 MHz scope.

Finding faults in circuits (you own or just build after a schematics) is part of the fun.

I remember an amplifier that worked quite well as a radio receiver for a Russian language station. I never found out the frequency, as the normal radio I had could not get that station (e.g. outside the normal bands).
 

Offline blueskull

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Re: When you follow the schematic but it doesn't work
« Reply #17 on: July 25, 2018, 12:34:58 pm »
You are quoting one extreme of the spectrum.  I am sure there are some amazing professors on the other extreme and a bunch of average in between.  Look for the world changing extreme, not the mediocre one.

I don't think so. Most of the time I see a person who knows all is an undergrad. The higher the education, the less the common ECE background knowledge one retains from BS education.

Most truly amazing Swiss knife engineers I've ever seen are either tinker/hobbyist on their own (learn by passion) or are just never received graduate education.
 
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Online GeorgeOfTheJungle

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Re: When you follow the schematic but it doesn't work
« Reply #18 on: July 25, 2018, 01:26:16 pm »
I remember an amplifier that worked quite well as a radio receiver for a Russian language station. I never found out the frequency, as the normal radio I had could not get that station (e.g. outside the normal bands).

I once managed to do exactly that with a mixer :-) it had a few audio inputs, a few buffer opamps and CMOS analog switches, every now and then I could hear the radio :-). Had to put some low pass filters.
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Online rsjsouza

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Re: When you follow the schematic but it doesn't work
« Reply #19 on: July 25, 2018, 03:23:41 pm »
You are quoting one extreme of the spectrum.  I am sure there are some amazing professors on the other extreme and a bunch of average in between.  Look for the world changing extreme, not the mediocre one.

I don't think so. Most of the time I see a person who knows all is an undergrad. The higher the education, the less the common ECE background knowledge one retains from BS education.

Most truly amazing Swiss knife engineers I've ever seen are either tinker/hobbyist on their own (learn by passion) or are just never received graduate education.
In my life I have seen examples in any direction. When I started in the university I had the same impression with some professors, but over the years I found out that the ones that lead or were part of research labs were quite close to the metal, as they suffered with lack of money and resources and needed to build and teach the students how to build most of the infrastructure to get further goals. Also, the lack of resources also meant we were using 50's and 60's equipment well into the 90's and they needed to explain to us how they actually worked so we could understand its limitations to do our job.

In these days I also learned something else: no formal education can trump passion. When I entered the university, there were three of us that had some experience with electronics and couldn't wait to reach the point where actual electricity/electronics lectures would start. The basic course seemed insurmountable (Calculus, Diff Eqns, Complex Math, Mechanics, etc.) but the big carrot after that phase certainly eased the pain, at least for us. Many others dropped out of the university before finishing the basic course. 

If someone is truly passionate about anything, the formal education will become what you make of it - all these weekends and evenings studying things that were apparently disconnected from my core passion (electronics) only helped me broaden my horizons.
« Last Edit: July 25, 2018, 05:13:05 pm by rsjsouza »
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Oh, the "whys" of the datasheets... The information is there not to be an axiomatic truth, but instead each speck of data must be slowly inhaled while carefully performing a deep search inside oneself to find the true metaphysical sense...
 
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Offline b_force

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Re: When you follow the schematic but it doesn't work
« Reply #20 on: July 25, 2018, 03:27:41 pm »
Passion is indeed the most important thing of all.
The biggest key factor you're looking for as a company.
"If you can't explain it simply (or at all), you don't understand it well enough." A. Einstein

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Online GeorgeOfTheJungle

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Re: When you follow the schematic but it doesn't work
« Reply #21 on: July 25, 2018, 04:13:20 pm »
They're teaching C# and nodejs at my local college and their staff have absolutely no fucking idea what they are doing. We have had a couple of their "graduates" in on trial and we're basically having to get them to unlearn a lot of stuff. I mean you don't write an OO program entirely in static methods ffs. But that's what they told us. Seriously, no.

Node.js was a very nice little project at the beginning, but it has grown many legs and arms, five or six eyes, and two noses and three ears => it's ugly now. It went nuts when Ryan Dahl, the BDFL, left.
« Last Edit: July 25, 2018, 04:15:09 pm by GeorgeOfTheJungle »
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Online bd139

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Re: When you follow the schematic but it doesn't work
« Reply #22 on: July 25, 2018, 04:29:34 pm »
Yeah all the PHP holocaust perpetrators jumped on it then.

Now it’s “package manager of the hour” territory.
 

Online bd139

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Re: When you follow the schematic but it doesn't work
« Reply #23 on: July 25, 2018, 04:30:06 pm »
Passion is indeed the most important thing of all.
The biggest key factor you're looking for as a company.

I know lots of passionate people who are fucking useless.
 

Offline b_force

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Re: When you follow the schematic but it doesn't work
« Reply #24 on: July 25, 2018, 04:55:35 pm »
Passion is indeed the most important thing of all.
The biggest key factor you're looking for as a company.

I know lots of passionate people who are fucking useless.
Lol. Well there are also lots of people with a degree that are equally useless.
So i guess that's a draw.
« Last Edit: July 25, 2018, 05:01:31 pm by b_force »
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