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Forum Index : Microcontroller and PC projects : What is your favourite hardware problem?
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LeoNicolas Guru  Joined: 07/10/2020 Location: CanadaPosts: 479 |
When sound crashes you computer https://m.youtube.com/watch?v=TB5IFVkMMIw&list=PLlrxD0HtieHhDTjMijDOd0BSJcpSFabfE&index=1&pp=iAQB |
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SimpleSafeName Guru Joined: 28/07/2019 Location: United StatesPosts: 319 |
When I found that I could double the memory on a GE Series Six PLC by soldering in a jumper. Save the company that I worked for about $40K (that was in 1991, works out to be about $92K today) in cost avoidance by not having to buy new memory boards. BTW, the new boards were about $4k each. And that was for 8K of RAM. Those were the days... The 4K boards were physically the same as the 8K ones with the exception that jumper JP7 had been removed on the smaller boards. GE was not amused... |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 857 |
E-Stop button  It's arguably a bad business model but I do my darndest to solve customer's machine problems remotely but hey, they're only spending company money so what do they care. It was obvious that the problem of "not starting" was due to something in the hard-wired E-stop loop. I insisted, repeatedly that they needed to trace the open-circuit. Ended-up with a day-trip at industry rates. Walked to the back of the machine and found a latching E-stop button had been pressed. Quick twist-release and all was good. Nice sunny day and I found a really nice restaurant near to the train station and so I had a loooong leisurely lunch, sitting outside (glad I decided not to drive ) |
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| Volhout Guru Joined: 05/03/2018 Location: NetherlandsPosts: 4223 |
This was a problem then, but even more now. Since hardware cost is low, we typically add lots of filtering (capacitors, resistors) to lines like RESET, and do carefull gerber checks before going to the PCB manufacturer. Especially naughty is coupling from one layer to the next, and then especially to I2C lines, since these are relatively high impedance (pullup) and cannot be silenced with capacitors. Volhout PicomiteVGA PETSCII ROBOTS |
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Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6783 |
We had a few with the Nascom-1 and the RAM-A boards! The Nascom-1 used some National DM81LS97 octal buffer chips. How they were used was probably the problem, there were timing issues. Sometimes you had a system that didn't work and merely swapping over two apparently identical chips fixed it. They were also used on the buffer board, which was used to expand the Nascom-1 so that it could use the NASBUS so you often had spares there. The RAM-A board was fine if you got a good one, but could be virtually impossible to get stable if you didn't. It's problems even had a name - "Memory Plague". There were all sorts of "fixes" including adding wires to "grid out" the power rails. The RAM-A had a relatively short lifetime and was eventually replaced by the more capable (but more expensive) RAM-B board. These were actually two different boards despite the similar names. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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vegipete Guru Joined: 29/01/2013 Location: CanadaPosts: 1109 |
You have to love such problems. I had a call at 3 in the morning - one of the machines I was responsible for had stopped running, completely dead. I grabbed my kit and went to troubleshoot. The fault? The power cord had fallen out from the socket in the wall. Visit Vegipete's *Mite Library for cool programs. |
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| PhenixRising Guru Joined: 07/11/2023 Location: United KingdomPosts: 857 |
Yup  It can be really awkward when you're called-in as a last resort; the in-house tech has swapped-out all kinds of components ($$$$) and now has some crazy theory about what needs to be done. You find that it was something silly after-all but now you don't want the tech to look foolish to his management. I have actually, needlessly pulled-out my test equipment and scratched my head until no-one was watching and then switched-on the air-supply that someone had isolated but had forgotten about. I told the tech and he was devastated but I put together a BS report with lots of technobabble. |
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