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Operational amplifiers - how to check them quickly?

398216 Usunięty 2772 28
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  • Op-amp tester circuit board with function labels.
    As in the title - today, when integrated circuits have made themselves at home in all sorts of amateur electronic constructions - there is a problem with this. However, is it really?
    Of course, I'm not talking about programmable circuits or specialised ICs designed for a specific application - I'll deal with those containing virtually complete amplifier circuit(s), which have earned a well-deserved place at the forefront of audio technology.

    The principle is simple: instead of building "on foot" a preamplifier or an equalizer stage using transistors, resistors, capacitors, many of these components can be replaced by one small IC that already contains the "heart" for the whole. And for a specific application, it requires only a few additional components. At the same time, the quality of a preamplifier made in this way, for example, can surpass even systems from the "previous" (solid-state) era, plus it takes up less space!
    So much for the (greatly simplified!) introduction.

    Advantages abound, but for the amateur electronics technician, sometimes such an operational amplifier is something that one does not really know how it works and there is no (especially) way to verify it.
    Of course - you can take measurements with a meter, check the resistances on individual pins, comparing them with a working (brand new) circuit of the same type, but... but not everything can be explored in this way.
    So it would be advisable to approach the issue in a different way - to simulate a circuit typical of an operational amplifier and only then verify whether (and how!) it works.

    The problem is, however, that no one would likely want to make such a circuit, and moreover, measuring alone takes some time, and still does not always give us 100% certainty - especially if we do not have access to, for example, an oscilloscope. So is it possible to do things differently, more simply?
    It turns out that yes. It may not be possible to check the exact catalogue parameters in this way, but within seconds(!) we can verify whether the circuit is working at all. In most cases, this is sufficient. After all, we do not need to check whether the manufacturer's parameters are within a certain tolerance - it is enough to select a dedicated circuit for a specific application. And the catalogue parameters? Let's trust that the manufacturer knows what it's doing....
    So how can we test such circuits for potential failure?

    As I wrote - it's enough to build a test one, provide it with a socket (8- or 14-legged socket) and power it all somehow.
    Since the majority of circuits have a typical pinout system, we do not need to build an individual 'tester' for each. One, or rather three, will suffice - for single, double and quadruple circuits (i.e. those containing one, two or four amplifiers independent of the power supply in the structure).
    As for the electronic construction itself - it is enough to build an appropriate number (one, two or four) of secondary amplifiers (buffers) and to feed their inputs with the signal from the generator.
    And the signal for these amplifiers from where? For example, from a specialised 555 chip, on which we can easily build a SYMETRIC rectangular waveform generator with a relatively low frequency. A small one, so that we can "visually" see on the LED circuits connected to the outputs the waveform after "passing" through the amplifiers.
    And how do we check that the circuit is working properly?

    Simple: since we are feeding a symmetrical and rectangular signal, this is what we can expect at the WO (operational amplifier) outputs. Of course, the circuit itself should be supplied either with a symmetrical voltage (from two separate power supplies giving symmetrical voltage at the outputs, but with opposite polarity to each other), or create a so-called artificial ground from a single voltage.

    Both methods are equally good, although in some respects a symmetrical supply will be preferable. For our needs, however, a single one will suffice. And once upon a time (quite a few years ago), I built such a circuit - out of necessity, because I had quite an elaborate device to make, and because I had about a hundred operational amplifiers "FROM RECOVERY", I decided to use them as much as possible. The circuit works, admittedly, to this day, but - as it turns out - I wasn't the only one to come up with such an idea and very similar testers are on offer on AliExpress.

    The description itself may sound like black magic to electronics beginners, but in fact there is a very simple way out of this situation - purchase a 'ready-made' one on AliExpress precisely, where you will find an offer of such circuits from the place you can use them. All you need to do is supply voltage from a stabilised power supply (12V) and plug the circuit under test into the socket. Then it's straightforward - check how the LEDs connected to the outputs blink and, based on this observation, determine whether the circuit is good or not.

    And how should these LEDs flash? You have to answer this question yourself - the key is the SYMETRIC input signal. Of course, this is in an ideal situation - in practice, the performance of the test LEDs is affected by the parameters of the circuit under test itself. However - as I can confirm after having done a dozen or so test circuits that worked and those that I was sure were faulty - practice makes perfect. So, after a short time, we will be able to determine not only the efficiency, but also (in the case of abnormalities) in what way the tested circuit is damaged. After all - as I pointed out at the outset - the WO contains a practically complete amplifier structure inside.

    So much theory (deliberately simplified to the necessary minimum). In practice, the testers look like this:

    Operational amplifier tester on a printed circuit board.
    .

    Operational amplifier test board on AliExpress.
    .

    And closer:

    Operational amplifier tester with labeled components.
    .

    Both models work similarly. Both can check single, double and quadruple amplifiers. Both signal operation with LEDs connected to the outputs. And finally, both testers allow the widest variety of circuits to be tested quickly and reliably - provided they have typically spaced-out leads.
    And what does it look like in practice?
    I have prepared three videos: one showing the operation of a dual comparator (a specific type of operational amplifier) and a second and third of a typical dual circuit - a faulty WO and a functioning one:

    A functioning comparator:



    .

    WO damaged:





    WO functioning:



    .

    (There is an error in the description of one of the auctions regarding just the identification of the efficiency of the tested system - most likely due to an incorrect translation of the original text). .

    One of the testers (the one shown at the very beginning of the article) is a little more elaborate - it has a separate generator signal switch and generator control, plus the ability to operate in two frequency sub-bands for a more confident circuit check. Personally, I would recommend one for those of you who are (for now) "less involved" in electronics. We can also (this is a suggestion for the advanced) build a similar tester ourselves, according to the descriptions posted in this topic.

    Either way, I believe that the testers discussed can find a place among the measuring devices of any electronics technician - especially those specialising in audio.

    Regards.

    Cool? Ranking DIY
    About Author
    398216 Usunięty
    Level 43  
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    398216 Usunięty wrote 33102 posts with rating 8553, helped 3856 times. Been with us since 2015 year.
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  • #2 21458753
    acctr
    Level 38  
    The simplest tester should at least verify the basic characteristics of a working amplifier:
    - high input resistance
    - low output resistance
    - very high voltage gain.
    Whether this circuit verifies this is difficult to say because there is no schematic, but it looks like the opamps work in a secondary configuration with a large input signal, i.e. they perform a function more or less like a single transistor, or even a resistor. If we insert 220 R between the input and the output will the diode blink indicating a working opamp?
    It would be better to use generator circuits built on tested opamps operating at the edge of the worst parameters.

    398216 Usunięty wrote:
    As an example, from a specialised 555 chip, on which we can easily build a SYMETRIC rectangular waveform generator with a relatively low frequency.

    The 555 does not guarantee this, but by adding a flip-flop we get such a guarantee.
    Helpful post? Buy me a coffee.
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  • #3 21459058
    elukam
    Level 16  
    A basic dual operational amplifier or comparator costs less than a zloty IN RETAIL when you buy a few. To check such a circuit, even if one had a ready-made tester, costs more than it is worth.
    https://www.tme.eu/pl/katalog/?queryPhrase=lm...;productListOrderBy=1000014&onlyInStock=1
    https://www.tme.eu/pl/katalog/?queryPhrase=tl...;productListOrderBy=1000014&onlyInStock=1
    https://www.tme.eu/pl/katalog/?queryPhrase=lm...;productListOrderBy=1000014&onlyInStock=1
    It is simply not cost-effective to check thousands of LUTE ICs, assuming that sometimes you have to straighten the legs and change the socket a couple of times, which in total will take a whole day. Finally, there is no full guarantee that the chip is 100% operational, as many parameters are important and can fail.
  • #4 21459130
    CodeBoy
    Level 33  
    elukam wrote:
    A basic dual operational amplifier or comparator costs less than a zloty IN RETAIL when buying a few pieces. To check such a circuit, even if one had a tester ready, costs more than it is worth.
    https://www.tme.eu/pl/katalog/?queryPhrase=lm...;productListOrderBy=1000014&onlyInStock=1
    https://www.tme.eu/pl/katalog/?queryPhrase=tl...;productListOrderBy=1000014&onlyInStock=1
    https://www.tme.eu/pl/katalog/?queryPhrase=lm...;productListOrderBy=1000014&onlyInStock=1
    It is simply not cost-effective to check thousands of LUTE ICs, assuming that sometimes you have to straighten the legs and change the socket a couple of times, which in total will take a whole day. Finally, there is no full guarantee that the chip is 100% working, because many parameters are important and can fail.


    Contemporary probably yes, but as Removed mentioned, if you are repairing a vintage (deck type for example) and want it in original then .... they are not single pln :) and if you find me one I will gladly buy :) .
    I recently bought an opamp for 50zł , so it already pays for itself with this meter.

    in the same way I am now repairing a 1978 Akai R2R and there is an unobtainable operational amplifier, there are admittedly Chinese paintings, but before I risk 100zł it is better to check :)
  • #5 21459223
    elukam
    Level 16  
    It is certainly better to have such a tester than none at all if one is fiddling with the solderings.
    If I were repairing equipment from 40 years ago I certainly wouldn't use an operational amplifier "from the era", but a better contemporary one. Another thing is that the place of decks is in the trash, without exception :) .
    WO is best tested in a circuit, in the sense of the surest and cheapest good way.
    If you're buying the Chinese equivalent of a WO from years ago, there's probably some popular contemporary structure sitting inside.
  • #6 21459244
    398216 Usunięty
    Level 43  
    elukam wrote:
    if someone is playing with outlets
    .
    Maybe you haven't noticed, but I dedicate the vast majority of my articles to such "young talents", and such colleagues (not only - I gave my example for a reason) try not to throw away components collected for years (often just from recovering old boards). After all, you yourself admit that "it is better to have than not to have". - this applies not only to the tester.
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  • #7 21459277
    2konrafal1993
    Level 38  
    It is better to have than not to have, but practice has taught me that the best thing to do is to connect an oscilloscope to the output and a generator to the input and check that the WO does not distort the signal. A few times I had such a case that the WO gave a much lower voltage on one of the halves and it also happened that I had a distorted waveform at the output. In the beginning it is possible to assess whether the WO is alive at all, but there are cases when only an oscilloscope will show the defects of the circuit.
  • #8 21459376
    viayner
    Level 43  
    Hello,
    As I see it, this is a simple relaxation generator on a given OA.
    Layouts old and familiar, I don't see one here (unless I've overlooked it then I apologise), is there a caveat in the instructions as to what circuits it tests/tests? I ask because I don't see a topography change circuit, for example as you know quadruple circuits have power on different pins typically 4/11, but there are for example 7/11 (RC4136) or 7/14 (LM3900), 3/12 (LM2901).
    I ask because this should be indicated somewhere.
    Regards
  • #9 21459622
    398216 Usunięty
    Level 43  
    2konrafal1993 wrote:
    the best way to do this is to plug in an oscilloscope to the output and a generator on the input and check that the WO is not distorting the signal
    .
    398216 Usunięty wrote:
    Maybe my colleague hasn't noticed, but I dedicate the vast majority of my articles to just such "young talents"
    .
    Young Able mostly doesn't have an oscilloscope.
    viayner wrote:
    I ask because it should be marked somewhere.

    398216 Usunięty wrote:
    Because the majority of circuits have a typical pinout system, we do not need to build an individual "tester" for each. One, or rather three, are sufficient - for single, double and quadruple circuits (i.e. containing one, two or four amplifiers independent of the power supply in the structure).

    If the picture shows two 8 pin and one 14 pin sockets and the tester is described as an operational amplifier tester then I thought that was clear? And as for the unusual pinout of the power supply it is about that in the text - the testers described in the topic are designed for typical power supply pinout configurations.
    398216 Usunięty wrote:
    both testers allow for fast and reliable testing of a wide variety of circuits - provided they have typically spaced pins.
    .
    Yes, the first photo may be a little small, but later in the content it is repeated in large size. I am talking about the tester I recommended for the amateur - the second tester actually "supports" only chips in 8 pin enclosures.

    I see that the topic has generated interest - and that's good. This is what it's all about to share your own insights and experience.
    Thank you.
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  • #10 21459813
    ptero
    Level 24  
    @elukam - After all, you only buy a DECK to make the tower complete and look better, not to listen to old tapes.... :)

    Although to tell you the truth, I do have a few old cassettes, with tracks that can NEVER be found.
  • #11 21459863
    elukam
    Level 16  
    Since the topic is slowly turning into a discussion about the needs of the young able, I will write the following.
    When I myself was a young able-bodied person with no funds, but with a passion for electronics, I had no access to anything. The source of parts was old discarded tube receivers (literally), and friends whose parents picked up waste parts from various workplaces. My only measuring instrument was a Soviet measuring system I acquired somewhere, with a resistance divider added on the fly.
    Then, when I was older, I started visiting Bomis, where you could buy junk by weight and various odd bits of unspecified scrapped devices, as long as there was as much as you could get out of them.
    Systems were built not on the basis of what I wanted to do, but what I could do with what I had.
    Another source of parts was the Perski, Skra and later Wolumen electronics exchange, where you could buy almost all the treasures you needed from private importers and thieves with access to Diora, ZRK and other Unitra plants. But the prices were high.
    Then the only just system collapsed and suddenly it turned out that parts were plentiful and cheap. This happened overnight. Without too much effort you could buy a decent meter or even a simple oscilloscope. Even then, it was no longer practical to use disassembled parts.
    Today, a young able-bodied person can buy a simple but sufficient universal meter for the equivalent of THREE frozen soups. If he has the motivation and saves under 1000 PLN (one week's minimum wage), he will buy a simple oscilloscope. He does not have to go to a big city, he can easily order a packet of useful NEW parts from one of the specialist shops, with cheap home delivery. The parts are cheap as borscht. It is known that specialist ones are not, but the young able-bodied do not need such. In summary, there is a real eldorado for the young talented today. It is enough not to be lazy.
    Yes, I have plenty of parts from the old days. New and discarded. But I reach for them so rarely that I don't know if I should just throw them away. The only reason I haven't done this so far is probably because I hardly ever throw anything away, such is my sick nature. But I by no means encourage the young and talented to play around with cast-offs. Their quality is always suspect and there is no profit - there is a loss! Better to assemble something or read something in the meantime. Especially these popular soldered parts are simply worthless.
    Yes, old electronic boards are very useful for... learning to solder. Because all these contact boards are evil incarnate. You need thousands of hours to use a soldering iron efficiently, so for example soldering parts off boards makes sense. But without exaggeration.
  • #12 21459867
    Mlody_Zdolny
    Level 30  
    398216 Usunięty wrote:
    Young Talented mostly doesn't have an oscilloscope.

    E there, I even have three :D and any of them will do for this application.
  • #13 21459884
    elukam
    Level 16  
    @ptero Cassettes can be lost and burned to CD or converted to MP3.
    My decks are rotting in the attic, although I do own a stereo. Not as a retromania, just because the sound from modern Chinese stereos sucks. According to the tastes and expectations of the modern customer with the rest.
    There are many nicer or more practical things that decorate interiors better than a deck :) Or even a reel-to-reel with wooden sides set up vertically :) :) :) .
    Certain solutions have gone because they most simply no longer make sense and technical justification. If someone brings it back out of nostalgia, that's their business. Worse if they justify it technically, because that is already ridiculous or pathetic, as you prefer.
  • #14 21459960
    maciej_333
    Level 38  
    Is there a diagram of this circuit somewhere? You could at least comment on what this circuit does and if it has any use. I once bought a couple of TL082s. They seemed to work fine, but the problem was that with a ±15 V supply the output voltage could vary around ±10 V (correct circuit and load resistance, low input voltage frequency). Would this tester detect this?

    Generally most or all can be tested with this circuit: Link . They described it very nicely.
    Circuit diagram with operational amplifiers and switches. .
    [source]
  • #15 21459976
    acctr
    Level 38  
    maciej_333 wrote:
    Is there a schematic of this circuit somewhere? You could at least comment on what this circuit does and whether it has any use.
    .
    I couldn't find a schematic of the Chinese kit, but quite possibly it is based on something similar:
    Circuit diagram for testing single, dual, and quad operational amplifiers. .
    Helpful post? Buy me a coffee.
  • #16 21460028
    CodeBoy
    Level 33  
    elukam wrote:
    @ptero Cassettes can be lost and burned to CD or converted to MP3.
    My decks are rotting in the attic, although I do own a stereo. Not as a retromania, just because the sound from the modern Chinese is crap. According to the tastes and expectations of the modern customer with the rest.
    There are many nicer or more practical things that decorate interiors better than a deck :) Or even a reel-to-reel with wooden sides set up vertically :) :) :) .
    Certain solutions have gone because they most simply no longer make sense and technical justification. If someone brings it back out of nostalgia, that's their business. Worse if he justifies it technically, because that is already ridiculous or pathetic, as you prefer.


    You don't even know what kind of market there is for this and what kind of suction there is for the service, because just replacing belts is no longer enough. Look what you have in your attic because you may have some PLN e.g. Technics hold terribly good prices (for sellers). The fact that you do not use it does not mean that there is no "fashion" for it "modern" decks began to come out, they are mechanically hopeless but they are :)

    And if you want to get rid of these vintage decks let me know, because I could definitely use them for donors :)
  • #17 21460041
    acctr
    Level 38  
    CodeBoy wrote:
    Just because you don't use it doesn't mean it's not "in fashion" "modern" decks have started to come out, they are mechanically hopeless but they are
    .
    They've even started releasing new walkmans because MC sales are growing. But it's ugly, it doesn't compare to the basic models of old let alone the top slim sony/panasonic models.
    Helpful post? Buy me a coffee.
  • #18 21460056
    maciej_333
    Level 38  
    acctr wrote:
    maciej_333 wrote:
    Is there a schematic of this circuit somewhere? You could at least comment on what this circuit does and if it has any use.

    I couldn't find a schematic of the Chinese kit, but quite possibly it is based on something similar:
    Circuit diagram for testing single, dual, and quad operational amplifiers.
    .
    It is already possible to talk. So here we have just a rectangular waveform generator on IC1 and individual operational amplifiers as secondaries. There are oppositely connected diodes on the outputs to show that there is a polarity change. Something like this is ingenious, but it's just a test to see if the operational amplifier is perhaps undamaged. No reliable test it is not.

    It is good that at least there are R12, R14 and R15. Question for the reader. Why were these resistors used? Let's leave aside the obvious answer that the amplifier under test has some sort of input short to the power supply.
  • #19 21460057
    CodeBoy
    Level 33  
    acctr wrote:
    CodeBoy wrote:
    Just because you don't use it doesn't mean there isn't a "fashion" for it "modern" decks have started to come out, they are mechanically hopeless but they are
    .
    They've even started releasing new walkmans because MC sales are growing. But it's ugly, there's no comparison with the basic models of the past let alone the top slim sony/panasonic models.


    I agree they are mechanically hopeless and ugly, but the mere fact that new recorded cassettes are coming out in Empik proves something.
    That the quality is what it is (CC in general) agree, but you can see that people need the media and are turning away from files, very much so in the US CD sales have increased for probably the first time in over 10 years. The problem with cassettes is that there are no new clean ones, only either Chinese crap cut from VHS tape or NOS, but it also depends a lot on where they were stored.
  • #20 21460086
    elukam
    Level 16  
    CodeBoy wrote:
    the very fact that new recorded tapes are coming out in Empik proves something
    .
    The only thing it proves is that people are f*cking off, which is altogether a non-new, cyclical phenomenon. The same thing has happened before with tube amplifiers and vinyl records. Or even nix clocks.
    And when people fuck off, it is always the market that decides to make money out of it, because the best money is made by FRAYERS following fashion.
    I won't be at all surprised when cranked phonographs or wire recorders start to be mass-produced again. Audiophile ones, of course.
    CodeBoy wrote:
    And if you want to get rid of these relics let me know, because I'm sure I could use them for donations
    Maybe someday, for now for me they're such a money pit that it's not worth climbing into the attic for that, let alone packing and shipping. Let them rot with a whole heap of other discontinued rtv equipment I once used.
    The fact is that a few months ago I pulled down from the attic a brand-new Sony stereo I had once bought without the main module (radio-selector), bought the module at an auction (then they were unavailable, now they are), repaired the radio (curiosity - dual-band FM) and gave one of the family members at home a stereo as if straight from the factory, although 25 years old :) Only the VFD in the controller is already a bit burnt. But the decks from it have been left in the attic, no exaggeration :) .
    @acctr the last Sony walkman model I had ended up as a mechanical donor and was converted to a servo speedometer pointer for a bicycle speedometer :) Portable MP3 players have rightly ended the life of all walkmans and discmans.
  • #21 21460172
    398216 Usunięty
    Level 43  
    elukam - The greatest sin is to judge others according to yourself.
  • #22 21460184
    PPK
    Level 29  
    Not that I'm picking on you, but operating an LED in the reverse direction requires a catalogue check of the reverse voltage. I've had red ones like this that died already at 6V reverse voltage.
  • #23 21460233
    acctr
    Level 38  
    elukam wrote:
    Portable MP3 players have rightly ended the life of all walkmans and discmans.
    .
    Unfortunately, the sound quality of the plastic player decided this. But over time, players too have lost out to smartphones.
    However, the craftsmanship of the top walkmans, their styling will never go away.
    Helpful post? Buy me a coffee.
  • #24 21460566
    elukam
    Level 16  
    acctr wrote:
    The craftsmanship of the top walkmans, their styling will never go away
    It's hard to deny the admiration of these designs. But let's not exaggerate either. The mechanism of a miniature 8mm tape camera is incomparably more advanced and these cameras are no longer used at all, or what about mechanical calculators, which were literally slaughtered by digital calculators within a few months? That's where the mechanics were.
    We can be nostalgic, but let's not deny the FACTS that say that the quality of some equipment from the previous era simply did not stand up to competition and progress. And this undoubtedly includes magnetic tape recording and groove discs.
    From previous eras you can have excellent tuners, amplifiers, speakers. Because now they don't make better ones, only worse ones. But not tape recorders!
    When CDs appeared in the 1980s, no one denied that it was an excellent sound source compared to everything of the time. And today it is being denied. And it is done by mass dilettantes. Even though there has been SACD for a long time. Paranoia.
    398216 Usunięty wrote:
    The greatest sin is to judge others according to yourself.
    Some point of reference I guess you have to adopt. I'm a pretty good reference point, because I started playing with electronics from a kid, without any family background or support, persevered in it, educated myself to the max and finally it became my income and I even achieved some so-called success. Why shouldn't I relate to myself what others do and how they do it? There are extremely few people who have gone all the way like me. Personally, let me be clear - I do not know.
    I'm not going to, because I don't have the slightest reason to turn tail and feign false modesty. I know that it makes people in our country sick, but so what? Not my problem. The world is full of jealous people and losers who have missed something at some stage. I only appreciate those who don't give up and keep raising the bar. And these are the people I would like to help. Only such people move the world forward, the rest are worker ants, whether they are there or not - it makes no difference to the world.
  • #25 21460664
    398216 Usunięty
    Level 43  
    elukam wrote:
    I'm quite a reference
    .
    And what a humble one at that.... :)
    And seriously - do you think you were the only one to start out this way? That you were the only one to get to some level? May you not be disappointed.
    Let me repeat - don't judge others by yourself and respect the skills and knowledge of others. Perhaps they are smarter and perhaps have a more realistic view of their own and others' skills. The fact that you do not know such people does not mean that there are no such people.

    Best regards.
  • #26 21460772
    acctr
    Level 38  
    elukam wrote:
    acctr wrote:
    The craftsmanship of the top walkmans, their styling will never go away
    It is hard to deny the admiration of these designs. But let's not exaggerate either. The mechanism of a miniature camera for 8mm tape is incomparably more advanced and these cameras are no longer used at all, or what about mechanical calculators, which were literally slaughtered by digital calculators within a few months? There it was just mechanics.
    .
    A mechanical calculator or a cassette-sized camera with a dolby system and soft mechanics? Poor comparison, I don't think you understand what I'm writing about.
    Helpful post? Buy me a coffee.
  • #27 21460779
    elukam
    Level 16  
    @398216 Usunięty Read to the end, referring, I already wrote about modesty. Modesty is for suckers. In the whole world who achieves something. In Poland hardly anyone achieves anything, MIERNOTA dominates, often associated in mutual adoration clubs, so modesty is a national virtue and is absolutely required in the public sphere under threat of banishment.
    Nowhere did I write that the only one. Hit the table...
    I respect a great many people. I will say more than that, I do not judge before I know enough to judge. I do not have to agree with them at all. It is a sign of embarrassing smallness, translating sympathy into respect. And I have no doubt that a lot of people I don't know know know more than me. People in general are capable of impressive things. SELECTED. There are a lot of them quantitatively, but percentage-wise it's a handful.
    But maybe let's stop, because it's pathetic to walk in on someone on a topic portal. Don't you think? Do you swallow?

    Added after 1 [hour] 4 [minutes]: .

    @acctr https://kwejk.pl/obrazek/2164093/mechaniczny-kalkulator.html
    https://fr.wikipedia.org/wiki/Fichier:Calculator_divisumma24_hg.jpg
    https://www.dobreprogramy.pl/maszyna-roznicow...h-w-wysokiej-rozdzielczosci,6628008402348161a


    Moderated By ArturAVS:

    3.1.9. Disseminate content that is ironic, mocking or malicious, which constitutes a sign of disrespect towards other Users or third parties.

    .
  • #28 21461002
    żarówka rtęciowa
    Level 37  
    Hello

    Operational amplifiers are fairly versatile components and can be used to make a lot of trinkets, e.g. flashing LED Christmas tree lights, or useful circuits such as a sine wave generator or a semiconductor diode tester powered by 7.4 V Li-Ion batteries.

    elukam wrote:
    A basic dual operational amplifier or comparator costs less than a zloty IN RETAIL when buying a few pieces. To check such a circuit, even if one had a ready-made tester, costs more than it is worth.


    This is partly true. Unfortunately, stationary shops are being closed down, and buying from a Polish online shop means that you have to wait even a few days.
  • #29 21461164
    elukam
    Level 16  
    Stationary shops are being closed down because they are making a loss. Parts are cheap (that's the point) and customers are scarce.
    A shipment from TME normally arrives by courier on the second working day. Let's say that somewhere in the deep provinces it goes 2 days. Such a tragedy? There life goes 5x slower anyway ;) .
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Topic summary

The discussion revolves around methods for quickly checking operational amplifiers (op-amps) in electronic circuits, particularly in the context of amateur electronics and vintage equipment repair. Participants suggest various testing techniques, including using basic testers to verify input/output resistance and voltage gain, as well as employing oscilloscopes and signal generators for more accurate assessments. The cost-effectiveness of testing versus replacing op-amps is debated, with some emphasizing the importance of preserving vintage components. Specific op-amp models like LM358, TL072, and LM393 are mentioned, along with the challenges of sourcing older components. The conversation also touches on the nostalgia for vintage audio equipment and the evolving market for such devices.
Summary generated by the language model.
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