4 ms·
This is more common than one would think. I've done something like this several times before, too -- not taking photographs, but reviewing the actual board agai
by alxlaz 8y ago
This is more common than one would think. I've done something like this several times before, too -- not taking photographs, but reviewing the actual board against the layout and specs. I found unspecced parts twice; the first time it was pretty innocent, just a couple of 0-ohm resistors that weren't marked on the schematics (understandable from ODMs who want to reuse the same design but annoying to debug when it goes wrong). The second time it was a pair of clamping diodes that should have been there from the very beginning (I don't know how it slipped by the initial schematic review; I wasn't working there when it happened). They weren't on any schematics, and when we requested an up-to-date BoM, they were tucked away under another set of diodes, despite being a different part.
I also found parts that had been changed without notice (one of which had the potential to be tons of fun because it was a crystal oscillator with a far worse tolerance than the original).
When the supply chain itself, the management effort and the handling of the supply chain gets so large that it's done almost completely overseas, by a whole team of different people, under constant time pressure and in various degrees of partnerships with other companies (not just those who sell the supplies), these things can slip between the cracks surprisingly easy.
- agumonkey 8y agoI'm waiting for someone to say that pcb are designed with dummy traces added to allow for manufacturer to make stupid changes without harming anything
- alxlaz 8y agoNot necessarily for that, but it does routinely happen that an ODM uses the same PCB design for multiple projects. This results in various chips remaining unpopulated, 0-ohm resistors used here and there to route pins to the right peripheral and so on. As for stupid changes, while I don't remember the details now, I definitely remember drafting at least one schematic that supported accessing the same peripheral in different ways (or something of this type?) because we couldn't figure out the best one (or the right one?) from the datasheet. It's definitely the kind of thing that I'd rather not see in a final design, and which I'd iron out in a subsequent revision, but I suppose if you work under the consumer industry's tight deadlines... Oh, and of course, some PCB traces literally don't lead anywhere in the connection sense. E.g. guard rings aren't there to connect electronics together. I suppose it wouldn't be hard to mask some malicious connections that way.
- agumonkey 8y agoOh yeah, since I started scraping electronics I see how often boards are designed for multiple price points :) there's indeed a lot of place to toy with.