2021-01-01 - too much engineering

last year (i.e. couple of days ago) i bought some USB disk adapter for my mum, so that she can move (and backup) some of her stuff off from her laptop. aside from shitty interiors design (connectors were covered by cables and thus it was hard to plug in disk so that no connector gets damaged) one more thing stand out – after plugging in both USB and 12V, it did not work. it was cheap stuff, so i though “yea – again…” but since i happen to be an engineer i though – meh, probably sth trivial – will just fix it on my own most likely. and so the investigation started.

first of all it was detected by USB host. the disk however was not spinning. since it had an external power cable i assumed that electronics is powered from USB and disk is spun with external 12V PSU. this could explain the effect.

since the disk i got was neither mine nor new, i though it might as well be broken, too. however swapping to another disk from a closet had the same effect, i narrowed down the search to the USB adapter.

while the design was shitty, the good thing is that power supply line to disk was THT-mounted, so i could just attach my multimeter to it and see if there is any power supply to the disk, from the board… and as expected – there was none.

so the next thing was to check cables from 12V PSU socket to the adapters PCB. again luckily it was easy to access… and again – no power.

must the PSU then. at that point i did though i could have just checked it right away and spare myself tracing PCB lines, but whatever – we already know where the problem is. quick check on the PSU's cable and – bingo again. no power!

at this point i was ready to ship back my new, shitty adapter… and it struck me. then i was wrapping it all back to the box, i've noticed that PSU just jumped out slightly from my wall power socket! just a bit, but enough to be effectively disconnected! pushing it to where it should be happened to “fix” the PSU issue!

so yea – things work better when they are plugged in… more over – to find it out i had to know some USB stuff, had basic electronics skills and tools to measure voltages. now what would anyone w/o any of these skills do instead? probably tried to plug it in again and fix it right away! to me it took like 10 minutes (screws, tools and stuff) – totally wasted. sometimes knowing too much can be a burden, as your brain just might be looking for a challenge that simply isn't there. just start with easy things first – there are plenty of real, interesting problems out the to try yourself up against… ;)

oh – i've almost forgot. at the end of the day i had to ship the really shitty adapter back anyway. even though i manged to make it spin and connect to a PC, it had some random R/W errors, at random locations, and on multiple hard drives. after receiving reimbursement and investing additional 5-10 EUR in a more decent model, it all worked like a charm since day one. as they say in Germany: buy cheap – buy twice.