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Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by dylan604 on Friday November 20, 2020 @12:08PM (#25162427)
it would be interesting to see if the same "wrong" resistor was used on multiple boards in the same position, or if the stack of resistors loaded into the robot just had one out of place resistor. if it was just a one off, thinking of the odds that one component out of the many on the board, the one board found it's way to the one guy that is skilled enough to not only notice, but do find out what, and have the proper component to swap out. I'd be buying lottery tickets if it were me.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by jjoonathan on Friday November 20, 2020 @12:20PM (#25162578)
I'm not convinced it was the wrong resistor, it could have had the correct value until someone (not necessarily OP) grabbed the board wrong, dropped it, or dropped something on it, and scraped some of the conductive layer.

In any case, having covered circuit boards is a critical part of the reliability equation in consumer electronics. In an EE environment, component-level access and visibility can make it worthwhile to deal with naked boards, but you inevitably drop a few nines of reliability.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by fest on Friday November 20, 2020 @01:20PM (#25163231)
The scenario you describe is very unlikely (the conductive part of chip resistor is enclosed in protective coating).

What is a lot more likely is one of the following:

* Engineer sent incorrect assembly drawing (sometimes when components are shuffled around with silkscreen/assy drawing layer hidden, the label for component can end up in unexpected place).

* Someone manually updated the part numbers from one revision to another and missed the one resistor.

* A new engineer joined a project, and after minor unrelated change to project, regenerated the fabrication outputs as one should. But he was not aware of changes somebody else did in BOM file by hand.

* PCB assembly was performed by hand for prototype and contained an incorrectly placed part, but the assembled PCB ended up being shipped because of complete lack of production planning, somebody in sales selling stuff before it's ready and this being the only option to avoid contract cancellation.

I have personally witnessed every one of these and then some.

Yes, product engineering sometimes really is that shoddy and people being people stupid things.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by jjoonathan on Friday November 20, 2020 @02:21PM (#25163877)
I spoke from experience, not from speculation.

No, resistors are not always fully encapsulated, especially if they are small, cheap, and/or designated for high speed applications, and no, the ones that are encapsulated are not protected well enough to make high or intermittent resistance failure modes particularly unlikely after being poked. I've seen both cracking and scraping in the wild. Not as many as I've seen shorted MLCCs, but that would be a tall order.

Sure, it could also have been a design failure, but every time I've found one bad resistor in a bank of identical resistors, it has always been a physical problem with that resistor. Shrug.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by carlsonmark on Friday November 20, 2020 @04:36PM (#25165315)
Disclaimer: I'm a software guy

Another source of cracking could be related to moisture in the SMD components. We do primarily small volume PCB runs where I work. In house, with parts stored here, pick-and-placed here, etc. We have had components crack as well, and I recall one of the suspicions being the source of the components. They were a supposedly reliable supplier, but components from them failed more often than those from another supplier so we stopped getting parts from them.

I am not sure if resistors are as prone to humidity effects, but if plastic parts are not humidity controlled before going into a reflow oven, they are prone to cracking. Even as a software guy, I have seen several brand new boards with cracked components on them over the last 15 years. Often the cracked components are difficult to find, since they are so small and do not fail completely (they are just off by a wide margin.)

https://www.ti.com/lit/an/snoa300a/snoa300a.pdf

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by fest on Friday November 20, 2020 @03:37PM (#25164669)
That is indeed interesting, I haven't seen it in the wild. Lot's of bad solder joints, shorted MLCCs- sure. I'm now tempted to scratch the ones used in designs I have access to.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by utopcell on Friday November 20, 2020 @02:30PM (#25163957)
smd resistors come in reels so it is not possible to have an out-of-place resistor. What is possible is that the pick and place machine that assembled it had multiple reels for the same part value, or that a reel finished in the middle of an assembly (less likely).
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by walrus01 on Friday November 20, 2020 @03:09PM (#25164399)
It would not be possible for just one SMD resistor to be the wrong value, they come in bulk packaging where every unit is identical from the factory.

https://www.google.com/search?q=smd+resistor+tape&client=fir...

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by HeyLaughingBoy on Friday November 20, 2020 @04:07PM (#25164950)
Not if it's on tape & reel with automatic P&P, I agree. But if those boards are made in such small quantities that they're being hand-stuffed, I wouldn't be surprised to see an errant resistor somewhere. Maybe the human pick&place was distracted and picked from the wrong reel, or 100 resistors were dumped into a bulk tray and there was a 400ohm resistor on the bottom of that tray or any number of scenarios.

I've seen so many assembly errors in my time that I'm pretty sure it was something like this that happened.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by antonf on Friday November 20, 2020 @04:52PM (#25165497)
Or PnP machine didn't place the resistor or misplaced the resistor because coordinates were wrong in PnP program, it was found by AOI machine, and then wrong resistor could be placed by rework technician.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by okl on Friday November 20, 2020 @03:39PM (#25164686)
Who knows what happened at that factory, maybe someone made a mistake. The part might also just have failed.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by Jdjdjdjjdhebe on Friday November 20, 2020 @12:44PM (#25162856)
One girl, Kate
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by dylan604 on Friday November 20, 2020 @12:59PM (#25163013)
never even looked at the credit for the article. "this guy" was just a generic reference to random person I don't know. kind of like Canadians refer to anyone as buddy.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by mplewis on Friday November 20, 2020 @01:27PM (#25163301)
Guy isn't a gender-neutral term.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by reaperducer on Friday November 20, 2020 @01:49PM (#25163543)
Guy isn't a gender-neutral term.

It is in many places. See my comment elsewhere in this thread. You may be unfamiliar with it in gender-neutral use, but it does exist.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by jsolson on Friday November 20, 2020 @01:14PM (#25163171)
Unlike buddy, it's an inaccurate generic reference. It's a little more typing, but replacing "guy" with "person" or in this case "engineer" would be more precise (and inclusive).
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by reaperducer on Friday November 20, 2020 @01:20PM (#25163233)
"Guy" is a perfectly acceptable word for a man or a woman in much of the United States. When the PBS children's show The Electric Company starts with the cry, "Hey, you guys!" it is not excluding the female of the species. It's an idiom.

There are places where "you guys" is unusual. For example, when I moved to a certain part of Texas, it was unfamiliar to the people living there. Perhaps you live in a place where "guys" is uncommon and are unfamiliar with the term. In that case, I suggest you respect other people's cultures and embrace diversity.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by beervirus on Friday November 20, 2020 @01:41PM (#25163457)
“You guys” is only uncommon in Texas because we have the shorter “y’all.”
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by edgyquant on Friday November 20, 2020 @01:55PM (#25163612)
That isn’t just Texas even as far north as Kentucky and the Southern bits of Illinois and Indiana people use y’all.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by nqzero on Friday November 20, 2020 @01:24PM (#25163270)
in the plural or non-countable, such as this case, "guy" is ungendered
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by reaperducer on Friday November 20, 2020 @01:53PM (#25163581)
Exactly. For example, the phrase "bad guy" could apply to a man or a woman. You can't just change that to "bad girl" and keep the meaning. "Bad girl" means something else entirely.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by inimino on Friday November 20, 2020 @01:35PM (#25163380)
"The one guy" is literally the opposite of uncountable.

Guys, this doesn't have to be so hard. Just check the authorship before commenting about the author! If you get it wrong and someone points it out, say "oops, I should have checked" and it's over.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by beervirus on Friday November 20, 2020 @01:42PM (#25163468)
> Guys, this doesn't have to be so hard.

Please don’t assume our gender when preaching to us about inclusive language.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by jsolson on Saturday November 21, 2020 @01:31AM (#25168193)
I debated calling this out and decided against because I knew you all would do it for me.

This, right here, is precisely why this issue is important. We have gendered pronouns that are so ingrained we try to pretend they're not gendered.

"All" is a _shorter_ and more inclusive substitute for "guys".

If you think this isn't important, just replace every occurance of "guys" that you see with "gals". If you're cool with that, good on you, but if you think for one second "oh don't say gals that might piss someone off" then, well, there's the kicker.

Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by inimino on Saturday November 21, 2020 @07:58PM (#25173928)
I thought using "guys" in a conversation about the use of the word "guys" would be obvious enough to register as tongue-in-cheek. But y'all went and proved me wrong!
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by jessaustin on Friday November 20, 2020 @05:07PM (#25165641)
IME, gals aren't making these mistakes, and also aren't doubling down when called on them.
Re:AB07-USB3FMC: The $1.65k eval board they can't be bothere... by reaperducer on Friday November 20, 2020 @09:33PM (#25167470)
IME, gals aren't making these mistakes

Then you have limited E.