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Most embarrassing junior tech moment? Go!
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Alex Eisenhut:
My first design that I also did the layout for had all the electrolytic caps backwards. I like to think there was a bug in the OrCAD library but still... :palm:
hans:
Was called in to look at a particular customers field terminal, which had a SBC that emitted a ton of EMI. It was a chronic issue, but since its a small company with little cashflow, it was fixed on a case-by-case basis (only customers that listened to particular FM radio stations on their tractor). A wide recall was out the question.

We were also unsure about "the fix" the employ, because all field terminals were hand built and had slightly different interface boards etc.
Usually "the fix" would include grinding down powdercoats internally, using copper tape around all plastics to create a faraday cage. And adding the highest impedance 10A+ ferrite beads we could find on ANY power line and extra beads on data signals. I was called on to look at it early in the morning. I mean, before coffee time :-// So what do you do with a drowsy mind after adding a power ferrite? Swap +12V and GND on a 20A bench supply, ofcourse. :-/O

Poof. :-BROKE

Luckily no customer data lost. The SBC had to be replaced with a newer faster model, which didnt had these EMI issues. However it included an overhaul of all interface boards, labour, etc. so was a few hours works for one of the production guys.

I went to my boss with good and bad news: the bad news is I blew up this EMI-troubled SBC, so that terminal needs a complete refurb, which costs us money... but the good news is we now have one less of these awful SBCs out in the field. Honestly, that SBC was a ticking time bomb, as it was haunted by many other issues in the years following.
globoy:
One of my first circuit board designs as a fairly new EE.  A video graphics board for an engineering workstation using VRAMs (dual-ported dynamic RAMs used back in the day in graphics systems).  Whole bank of them.  Got a prototype board back, could not get it to work.  The VRAMs seemed completely dead even thought it looked like power and signals to them were fine.  After some time of searching for every possible explanation, I realized I had used the pinout for the DIP package variant even though they were SIP devices (I guess I made the wrong association for the CAD program).  I was so depressed because in those days getting prototype boards was a many week affair and expensive.  But my boss said that the two packages used the same die so very possibly the signals were in the same order.  He was right!  Solution was to move each part up six positions and wire 6 wires back to the now empty mounting holes.  Thankfully I had a tech to do the dirty work.  Board worked like a charm.  His comment was, "well you learned something didn't you".  I never forgot that bit of leadership.
TopQuark:
First year in uni, was in the robotics team competing in Shenzhen for a competition called RoboMaster. (Fleet of ground robots and drones firing plastic pellets and golf balls at each other)

Competition rules dictate robots cannot draw more than 80W from the battery or it will be automatically shutdown for safety reasons (over speeding). I spent the whole year designing a system that stores surplus energy into a supercapacitor bank when the robot draws below 80W, and gives the robot an extra boost (>800W) from the super cap bank on command.

Anyways, after nights of sleep deprivation and sleeping on the floor (we stood up the bed in the hotel room to fit the robots), the night before round of 16 at 5am, I hooked the 5 assembled systems one by one up to a power supply so that I can flash the newest firmware to the controller board. First controller board didn't respond to the debug probe, nor did the second one, nor the third and fourth one. I finally realised something was up and started to probe around with a multimeter.

Well turns out despite using a polarised connector, I hooked the power supply lead up in reverse to the supply, and silently killed 4 out of 5 systems. I did design in reverse polarity protection, but never had the heart to actually test it before hand for fear of killing my precious creations. Well at the end I tested it the hard way, and turns out it didn't work properly.  ::)

Anyways, the remaining system worked fine, and broke the all time speed record in the competition. Future versions of the game rules severely limited the amount of capacitive energy storage allowed in a robot, so I believe my speed record still holds today.
KE5FX:

--- Quote from: jonpaul on May 12, 2023, 11:03:53 am ---1970 my second job as an EE.
Vibration/Real Time FFT analyzer system in 6' rack.
Drove  to demo at  Wash DC  wtih  my  manager.

In the hotel room, Assembled units into the rack, and plugged in 100 pin cable connectors.

Turn ON! HUGE bang , smoke from EVERY rack unit!

--- End quote ---

Amazing that you were able to recover from that in one night.   :-BROKE  Was that the HP 5451A?

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