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Why do companies try to take patents out on standard schematics?
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Just_another_Dave:

--- Quote from: coppercone2 on November 15, 2021, 11:03:45 pm ---
--- Quote ---I agree that a simple circuits shouldn't require peer review, but is it worth trying to keep basic designs secret?

And even reasonably experienced people do occasionally make silly mistakes.  The classic is using the wrong footprint, because the CAD library or data sheet contained an error, they missed.

I disagree with you about diluting the blame. Ultimately the person who signs off a design bares the ultimate responsibility, but playing the blame game all the time, is counterproductive.

--- End quote ---

The mistakes that are the worst and most overlooked are the simple ones. Double checking someones power dissipation, loads, etc.. often finds problems when something 'easy' was pushed out the door that is running a part hot or bad. Those are the best bugs to find because the explanations are concrete, the correction is simpler, and the re-cert process is easier/cheaper... and such a change is usually regarded as a solid win, even from nontechnical managers since its easy to understand and is the engineering equivalent of leaving your fly unzipped. So they just say 'thanks for noticing that', make a board revision and you are on your way without debating voodoo.

The simple mistakes are made by advanced people because either
1) too many rules of thumb
2) rush job
3) too boring/simple to verify and you are sure of yourself
4) overconfidence (LED are easy!!)

and they often have the most catastrophic consequences because thats how you take out a power rail to a control system, have a 'dead' light, explode MOV and so forth.


Would you rather
1) explain to some board why you want a better power factor correction circuit for the 2nd stage boost circuit because "its a good idea based on industry trends" despite "expectations to substantially increase cost"
2) tell the board "we need to replace a 0.04$ resistor with a 0.04$ resistor of a different size so we can get the temperature down from deep fryer to toasty, and it will slow down the telephone calls"

--- End quote ---

The first PCB I designed when I started working as an electronic university was reviewed by two senior engineers and an additional experienced engineer to check that there were no mistakes (we were in a rush and they wanted to ensure that the first prototype was perfect). None of us realized that I had forgotten to add mounting holes to attach legs to it (which was important due to the amount of conductive rubbish embedded on the tables of the lab) :-DD
coppercone2:
thats not exactly a game changer for a company (at least you caught it in the revision stage), try overheating parts hidden in power modules hidden in cabinets causing synchronized age related problems down the line.. but the point is the same. (at least the part was complex and the resistor was somewhat large, but there was a lack of thermal testing performed, so it was a little surprising that there was a problem given the circuit element size, if you had no idea about how power electronics behave. Like if a SMD fanatic guy sees a cement leaded power resistor they pretty much think Pmax=∞, rather then a reasonable watt number (compared to the 1/6 watt they are used to), so it was not investigated because it 'looked right' compared to the size of the capacitors and transistors as far as I can tell. The resistor specs are unfortunately not as impressive as their large size! a block of cement is not a heat sink. The part should have either been a even larger ceramic or a heat sink mounted resistor, and the module designer contracting company should have been scrutinized more despite their reputation

I can imagine another 'screw up' being related to screws and ground clearance or connection. I.e. the screw head chosen is too big so it shorts out something.  That will get you eventually if you mix up screws during disassembly, so i recommend a divider tray. or a screw mixup in the factory that makes sparks on first test because there were different head size screws used by accident.
AaronD:

--- Quote from: coppercone2 on November 16, 2021, 10:26:39 pm ---I can imagine another 'screw up' being related to screws and ground clearance or connection. I.e. the screw head chosen is too big so it shorts out something.  That will get you eventually if you mix up screws during disassembly, so i recommend a divider tray. or a screw mixup in the factory that makes sparks on first test because there were different head size screws used by accident.

--- End quote ---

I explained to a high school kid once, that he might have fried his exciting new computer build by putting the standoffs (weird screws?) on *top* of the main PCB, thus contacting the entire back of the board with the sheet metal case.  He brought it to an after-school function so I could look at it...*after* he tried to power it on and it "didn't work".  My diagnosis and his understanding of it were both immediate.

He corrected his mistake and said it worked, but I'm not sure for how long.  I lost track of him soon after.
coppercone2:
I broke a power supply because I over tightened a heat sink screw that caused a earth ground contact in a circuit point that was non standard and when I had to earth reference the supply it discharged a capacitor bank into something (while it was hooked up in series to provide dual power rails!) and went into the trash because that supply had to be repaired way too many times.

So the screws provided by the manufacturer were too long, and as a result the electrical clearance was dependent on screw torque! I think this was sloppy, considering that the torque was reasonable for the size of screw used. I just wanted to make sure the thermal grease was working well, the correct screw torque with the screws provided felt insufficient  :(. I consider it a weird problem but I also think that "just another transistor replacement" mentality made me complacent with electrical checks, since I considered it to be a BS problem. I chose the PSu to repair from the repair pile because I was convinced I can make the easy stuff go away quick.. fat chance

I don't do motherboards much but I think this can easily happen on a weird case/mobo combination.
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