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Re^4: I came, I saw, I ...

by afoken (Abbot)
on Jul 06, 2017 at 22:29 UTC ( #1194411=note: print w/replies, xml ) Need Help??

in reply to Re^3: I came, I saw, I ...
in thread I came, I saw, I ...

I hope your dad didn't get in too much trouble for blowing the channel on the scope.

Well, he wasn't fired, and he did not have to pay the damage. In fact, the company was sold later, including his working contract (as usual in Germany at that time). During that time, when TV sets had still a potent high voltage supply and a CRT, a scope could easily be killed by measuring at the wrong place of a TV set with the wrong settings. Nobody is stupid enough to measure the 30 kV at the anode of the CRT, but focus and gate 2 also have a voltage that would be quite unhealty for a scope with a standard probe.

The most expensive equipment I blew up wasn't my fault. The PCB layout engineer changed the orientation of a square micro-controller by 90 degrees but forgot to update the board markets. When a technician installed a socket where the micro would go, she followed the board markings. When I got the board and plugged in the in-circuit emulator, the emulator's interface "pod" belched the magic smoke when I powered the board. That was only about US$2000 to replace.

That's the "oh f***ing s**t" moment. Misplacing the ICE connector is also quote common on our current project, but luckily the ICE is quite robust, cheap, and some really wise man has decided to use a connector pinout for the ICE that makes it really hard to kill the ICE or the controller. We would normally use a keyed connector on the PCB, but that exact version required for the ICE is either close to unobtainium or insanely expensive. And compatible solutions are simply too large. So we placed an unkeyed connector and a tiny dot indicating pin 1 on the PCBs. So far, we have killed no ICE, and except for my 24V mistake, no board.

A co-worker of mine was once subject to the same "fire works" due the same mistake (by a different PCB engineer), but the damage was US$30k.

And that's the moment when you decide to call it a day, go home, and try again the next day.

My dad had a similar experience during his first job in the R&D department of a major electronics company. Consumer hardware electronics still was full of tubes and some rare germanium and selenium semiconductors. Industry started first projects with expensive and brand-new silicium semiconductors. Bipolar transistors and diodes, with real wires, packed in metal cans. Not that black, wireless birdseed FET stuff in plastic and ceramic cases with far too many pads and unreadable markings. A single Si transistor cost 100 or more, in current money, and it had awful specs. Si transistors were still individuals, each with its own set of properties. Finding some pairs with similar behaviour could take a day. One day, one of the hardware engineers came with a sketch of a high-end, high-power, high-frequency, all-transistor amplifier, requiring about 20 of those expensive beasts, all paired, all wired in parallel, with paired resistors. Plus a few more smaller transistors to control the big ones, also paired. About 2 or 3 k in modern money, maybe more, just for the parts and a few days for the selection. "The exact spec does not matter, just find similar ones", he said. My dad build the amplifier, connected it to the dummy load (capable of heating away several kW) and a supply, switched on power to start adjusting the amplifier, and just saw all of the transistors die faster that he could switch off. He went to the engineer, confessed that he had just killed hardware worth more than he would earn in two or three months. "Oh well, I kinda expected that would happen. My fault. Damn. I will have to redesign that better." And that's all the engineer said. Buring 3 k (in current money) and one or two weeks of work just to test an idea was completely acceptable.

Looking at my damages over time, I see a quite good trend. The damages get smaller. Let's hope the best ...


Today I will gladly share my knowledge and experience, for there are no sweeter words than "I told you so". ;-)

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