Switching Transistors that Wouldn’t

Don was one of the worst engineers I’ve ever known. As a matter of fact, he is one of the dumbest people I’ve ever known. I have no idea how that guy made it through college. I have a few stories about Don. This is one of my favorites.

Don’s boss was getting exasperated with him. He couldn’t get basic assignments done and thought he was beneath doing documentation. He kept lobbying for more tasks but would screw up anything he was given. It was getting to a bad situation between Don and his boss one day when the phone rang from the production department. They had a new batch of boards going through that weren’t working. Don’s boss told Don that this could be his moment to shine. Don eagerly jumped in his car and drove over to the production building where he went to work.

The problem turned out to be the switching transistor on a flyback circuit. The switching transistor wasn’t getting turned on. Don went to work. Engineers of Don’s caliber have the indispensable research tool – the soldering iron. Don grabbed one and got to “redesigning” the switching circuit. He was at it for a good week. The production line was shut down while Don was working away with his soldering iron and he finally got it working. He increased the input drive to the point where the circuit worked “normally.” Don called his boss and told him he had the problem solved. Don’s boss was in the production building in a matter of minutes and was ready to check things out.

Don had all of the changes written up and was ready to demonstrate the before and after boards for his boss. Before he could get started, the boss picked up one of the unmodified boards. He looked at if for a good two seconds before his face started getting red. He composed himself pretty well under the circumstances and pointed out to Don that all of the switching transistors had been mounted backward.

Before they left, they had a couple of boards reworked to put the transistors in the right way. Everything worked fine. Don’s changes to drive the daylights out of the poor little transistors never got implemented.

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F as in Format

Michael was new to America. He was a Russian immigrant. He applied for a job and was immediately hired at the company where I worked at the time. He didn’t speak English, but through his interpreter claimed to have a Masters Degree in Computer Science from the University of Moscow. This was in 1980 during the cold war. I guess if anyone was skeptical as to whether Michael really had earned a degree from the University of Moscow they could have called up and asked, but as far as I know nobody ever did.

Michael was put in a group where they wrote software for automated test equipment. They had a very impressive system for that time built by Computer Automation. I don’t know whatever became of that company, but they made very good equipment for that time.

The first thing Michael needed to do in his new responsibility was to learn how to write test programs for in-circuit testing. Given that Michael knew neither English nor the programming language of the Computer Automation equipment, it was going to take him a while. Michael began by sitting down at the terminal with the user manual and started typing in commands and see what kind of response he got. It probably wasn’t such a bad idea except when he got up to the letter ‘F.’

As he had done with all of the commands up to this point, Michael typed in ‘Format’ and hit the enter key. The system came back and told him that if he continued, it would wipe out everything on the hard drive and asked whether he really wanted to continue. Of course, Michael typed in a ‘y’ for yes. It came back a second time and said something like ‘are you sure that you really want to do this’ to which Michael gave it a ‘y’ yet again. The system responded for a third warning and said that this was your last chance. If you continue from this point, it will wipe out the hard drive. Michael typed yet another ‘y’ and all the data was lost.

Needless to say, Michael’s co-workers were none too happy but were as understanding as could be. There was a couple of years worth of data that went away. Most things were backed up on tape and in those days it took a good while to get things restored as well as they could be. After a couple of weeks, they got things restored and the system was operational again. Michael went back to the commands that started with ‘A’ and back to learning the system. It took a few days for him to get back to ‘F.’ Sure enough, Michael still didn’t get the concept of what it meant to format and he typed out the command again. All three times the system warned Michael about what he was about to do. All three times he came back with another ‘y.’

Michael’s co-workers weren’t as understanding the first time. They restored the system again and told him never to do that again.

It worked for about three weeks after the second restoration when Michael got up to those ‘f’ commands yet again and the three ‘y’ responses to the questions as to whether he really wanted to do format.

The story goes that Michael eventually learned English, but I don’t think Michael ever learned any of the commands after those that started with ‘f’ since after the third restoration, the co-workers told him to sit at the desk away from the terminal and to never, ever touch the terminal again.

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The Time Delay

Years ago, I worked at an aerospace company.  Testing of finished products was always an issue.  Comprehensive tests were required for finished hardware.  The test stations were generally pretty complex systems, which had to exercise all inputs and outputs of production hardware before it could get shipped and installed in final aircraft.  Unfortunately, the engineers who ended up in the test equipment group often tended to be those who weren’t good enough to work on the actual products.

The best example of that I ever saw was a guy named John.  He was working on one of the aforementioned test setups and was assigned a very small part of a test system.  For his particular circuit, a time delay was required.  There are plenty of right ways to design a time delay, but none of these seemed to occur to John.  He obviously struggled with this one when the light bulb went on.  A 7404 hex inverter has a propagation delay of 9 nsec.  John grabbed his calculator and worked out the details of his “design.”  It turned out that eighty nine packages of 7404 hex inverters at six per package gave him the delay he needed, which was 4.8 usec.

Test equipment in most companies tends to be behind schedule, since more priority and attention is given to production product that turns into revenue.  There was no design review process for test equipment at this company and things tended to just get built.  John’s circuit that included his time delay circuit got built into three test stations.  I always felt sorry for the person in the lab that had to wire wrap all of those inverters in series.

When the tester finally got tested, John’s time delay didn’t work out so well.  Since all 534 inverters had the same temperature coefficient, the actual delay would drift way out of spec from the time the circuit got turned on until whenever the test got made.

John’s boss replaced the hex inverter delay circuit with a single 74123 monostable circuit.  It was hardly a precision time delay, but it was good enough for government work in the application it was used.  There was a lot of space left over on the board after all of those inverters were removed.  The poor person who had to wire wrap all of those inverters in the first place got the privilege of unwrapping all of them and implementing the monostable.

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Welcome to the World of Engineering

Everyone knows that to become an engineer is hard.  However, becoming a good engineer and keep your cool is harder.

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