A simple mistake?

[G6Tanuki]

Originally Posted by Biggles

First of all apologies to G6Tanuki. I seem to have touched a raw nerve there with my comment about video conference meetings.

No offence taken: I guess we all need to work within our own comfort-zones. Though known as a pedant who can spot a misplaced comma at 1000 yards [a skill that's saved one client half a million quid in a disputed contract] I'm really more at-home with video than written notes/minutes!

[McMurdo]

One of my first college lectures I attended was about oscilloscopes. One of those 'gather round the bench please' jobs. Armed with a 9V battery, the lecturer prodded the terminals with the scope leads to show us how the trace could show DC voltages. The trace flicked up briefly and went back to the centre line. After much head scratching and sending a student to get a new battery with the same result, he decided the scope was faulty. Always tactful, I raised my hand. 'Sir, what's the little dolly switch for, by the input socket?'. 'That's the ac/dc switch'. he replied. 'It allows you to show a small ac signal riding on a larger dc signal more easily'. 'How does it do that?' I asked. 'Well, the probe is connected through a small capacitor on the AC setting'. So, I asked, ' where's the switch at the moment, sir?'. He looked, then opened his mouth to reply, then flicked it from AC to DC. 'No-one likes a clever clogs' he snorted before resuming the demo.

I tried the tactful approach and failed.

[G8UWM-MildMartin]

It can be amusing in industry if, in a vaguely similar scenario, someone from a different department, akin to the oscilloscope demonstrator, borrows test equipment from our workshop that I know is not faulty, returns it, claiming it is faulty and buys a new one for their department and finds that is no more amenable to measuring circuit current clamped over a 3-core cable or connected straight across a 24-V supply. It is only at that point they will tell anyone what they were trying to do...

[dseymo1]

I spent much longer than intended this morning wiring up an oven and hob.
Looped the cable through the oven terminals nice and neatly to save cutting, taking care to leave enough to leave a long enough tail to reach the hob connection (far left, looking from the front).
Only when I went to connect the hob did I twig that 'far left' was with the hob turned upside-down for wiring, and when in working position the connection was 'near left', and needed another half-metre or so of cable - slightly more than I'd left spare!

[Biggles]

Ok, hands up who has forgotten to thread the cable through the sleeve in the top of those orange rubber mains plugs that you used to get from RS before carefully wiring the terminals up? I have lost count of the number of sleeves I have seen cut through by someone who has forgotten and cannot be bothered to take it all apart again. I sometimes solder a banana plug on then remember you have to put the wire through the plastic cap before doing that. BNC plugs are the same. It hasn't improved with age either.
Alan.

[Refugee]

I once watched a workmate who had forgotten to put the strain relief onto the cable on a 10 way camera connector.
He put it in a sleeve stretcher in a vice and after an awful lot of trouble coaxed it over the plug.

[G6Tanuki]

When on a site I once wired up a 25-way "D" connector [soldered type, pink Hellerman sleeves over each soldered connection.... a real pukka job] only to then discover the diecast alloy cover sitting on the bench not threaded over the cable as intended.

D'oh! as they say. Fortunately I had a couple of metallised-plastic 'clamshell' types in my travel-kit so was able to maintain the RFI-proofness of the setup without needing to do a mass unsoldering!

I've also assembled Heliax-specific N-connectors only to realise that I forgot to put the shield-clamping nut over the cable. The centre-pin on these connectors is crimped and once fitted can't be removed/reused. The genuine Andrew connectors cost around £35 each....

[Biggles]

They are expensive indeed. We used a lot of Andrews' connectors, very nicely made, brass colour, on our mainsite equipment, mainly on LDF450/550 Heliax, semi rigid feeders. Good kit. I have seen water coming down the hollow inner "pipe" before when removing the connector. Not good. Means a lot of work ahead. I think I still have a couple of flanges around from dishes we took down in the distant past. I have no use for them but they are too nice to chuck out. Talking about connectors, another thing I have problems with getting my head round is when making up an extension lead of any description, say for example a 7 pin Din to 7 pin Din male to female. Now, to get the cores to match up correctly, when plugged in, which way do you start from? I have ended up with a mirror image before, and of course it didn't work.
Alan.

[TonyDuell]

When using those (excellent) EDAC516 plugs, I was pleased to see that the backshells can be dismantled and fitted over the cable after wiring the pins. I guess when you have around 100 connections that's important!

When wiring a DIN (or Dtype or...) extension lead, I normally wire one end, then wire a couple of pins on the other end and plug the connectors together to make sure those couple of wires match up in colour with the already-wired end. Saves having to redo the lot if I've got it wrong.

Another handy trick is to tie a loose knot in the cable before sliding the connector cover on. It stops the cover going right down the cable, falling off and getting lost (or worse, falling off and you not noticing it's fallen off before you fit the other cover and wire the other end.

I am told that cuttng the notch in a 13A plug cover because you've forgotten to fit it over the cable before wiring the plug will cause said plug to fail a PAT test. But I can't see how it makes the plug dangerous, it does not expose any live parts, for example.

[Boater Sam]

I am told that cuttng the notch in a 13A plug cover because you've forgotten to fit it over the cable before wiring the plug will cause said plug to fail a PAT test. But I can't see how it makes the plug dangerous, it does not expose any live parts, for example.

It constitutes a modified component, hence not allowed as it infringes the approval of the component.

[kevinaston1]

Many years ago, I had to conduct interviews for a new bench technician at work. One applicant was vastly overqualified for the job, but when I asked him why he had applied, he explained that there was little work available out there.

After a chat about himself and his past career, I gave him a little 10W audio amplifier along with its service manual, to repair as a bench test. He came to see me after a few minutes, and asked if he could have a writing pad and a pen? Of course, I said, handing one over. I left him to get on with it for 30 minutes or so.

He looked at me completely baffled, explaining that he had no gain from the first stage input operational amplifier; he had analysed the circuit, and it had no faults at all. I looked at the pad, and there were four A4 pages of textbook calculations analysing the first stage to perfection.

What is the op-amp’s supply voltage, I asked?

Oh, I never looked at that. Measuring it, he found zero volts, and then quickly discovered no volts anywhere; courtesy of a blown fuse, and a shorted rectifier diode.

Kevin

It is smoke which allows electronic components to work.

If you do something to make the smoke come out of them, the unit will stop working.

When you have put in new components, full of fresh smoke, the unit will work again.

[Biggles]

I would never entertain employing anyone without doing a practical test. It really sorts the men from the boys in a repair/maintenance environment. I have seen my fair share of bizarre results and strange theories over the years. You could tell within a couple of minutes who were going to be the main players in the job.
Alan.

[Ed_Dinning]

My self and one of my senior engineers were interviewing a guy for a development engineers job (power electronics, SCR's etc). He answered all the technical questions, understood commutation circuits and RMS device calculations.
We were showing him round the lab afterwards and he asked "what is this?". This was one of the latest, at the time, Weller temp controlled soldering irons in its spring mount!

Ed

[Argus25]

Ha, I have a similar story. In the early '80s I was interviewing technicians for a job repairing VCR's. We quickly found that the people making outrageous claims about their abilities had poor practical skills. One fellow claimed to be the co-inventor of about 5 different technologies.

So instead we came up with a practical test with a few work stations. One was circuits, and very simple questions about things like; what voltage would you expect on the transistor's collector ? (in a simple class A amp), or what would you expect this circuit to do ?(an oscillator) another station had a pile of unmarked transistors and a meter (an analog Hioki A-10 with a 22.5V battery in it for the Rx10k range) with the question, Identify the transistors as NPN or PNP. And another test with a soldering iron, wick & and sucker to remove some parts from a pcb. It was all child's play for an experienced technician.

These simple tests soon sorted out people with practical skills and experience fault finding circuits. One fellow even used the meter on the Rx10k range to identify the E & C of some of the transistors with with the knowledge of the different reverse breakdown voltages of those junctions and he knew the meter contained the 22.5V battery.

It was astonishing though, how many applicants with claims of competency, experience & qualifications couldn't pass a single one of the simple tests !

[MrBungle]

We had the same with software developers at my last contract outfit. The entry test had a 5-10% pass rate. We gave them a task which is to write a small program to solve a problem. They have two hours in which to do this. The arrogant laugh confidently because the program is quite simple. Then they get sat at the powered down workstation. About 5 minutes later they realise it has no operating system on it, it's not network cabled and step one requires working with two departments who they have never met and don't know where they are. And they've still got to write the program. The looks we got sometimes are quite funny. Many people actually said they liked the challenge. Two people just walked out swearing. Apparently having to earn your £90k entry salary is beyond people these days.

On the subject of electronics however, I did my school work experience working in the test gear department of a large company. There was a large pile of oscilloscopes and RF generators sitting there. Turned out they were the returns pool. Engineers were convinced they were broken and had returned them for new ones. They all checked out fine so they had the psychological concept of leaving them in the pile for a week before checking them out and restocking with no calibration or repair. It's amazing how often people think something is broken when they don't know how to use it! Some people were even convinced that certain scopes (mainly Philips ones) were cursed and kept serial number log books of equipment they wouldn't accept.

[mark_in_manc]

Originally Posted by MrBungle

Some people were even convinced that certain scopes (mainly Philips ones) were cursed and kept serial number log books of equipment they wouldn't accept.

The intersection of superstition and engineering is a pretty funny thing.

I was once in the staff room of a university engineering department when a new colleague (who, in her defence, was conscientious in the delivery of the more 'creative' courses she had recently been recruited to deliver, as the department tried to prop up flagging numbers on its 'hard science' offerings) mentioned that her and her partner slept on a magnetic bed, which was useful in aligning their chakras (or something) while they slept.

There was quite a long silence while people picked their jaws up off the floor.

Someone mentioned that if they wore tin-foil pajamas, they might be able to generate useful power as they turned in their sleep.

[Biggles]

The couple with the magnetic bed may even have received an electric shock if they wore a bangle with open ends. And it would be sensible to keep bedtime activity to a minimum to reduce this risk. Regarding equipment that is "jinxed", I think every workshop has the item of test equipment everyone avoids. We even had a remote radio transmitter site where unexplained things used to happen regularly. It wasn't my favourite place to be honest, especially when on callouts on dark winter nights on my own.
Alan.

I was given a paper test during an interview consisting of an single transistor amplifier once when applying for a job. It would have been a nice diversion except the setter used the same values and circuit (and questions) put forth in a Wireless World (WW) letter a couple of year earlier. I did quote the Ebbers Moll equation for the emitter resistance of bipolar transistors vs. current (for the bypassed emitter resistor case i.e 25 ohms per miliamp) but got it the wrong way up. I did say I read WW and it would have been a bit more challenging with different values. Still I got the job...

I think this counts as a simple mistake to keep it on topic.

[SiriusHardware]

Originally Posted by Ed_Dinning

Weller temp controlled soldering irons in its spring mount!
Ed

Ed- I've worked in / with electronics since the early seventies but had never set eyes on a temperature controlled iron until I started work in the early noughties for a company which did have them. So - depending on when this interview took place - I might have found myself in the same perplexed position as your interviewee.

[Tim]

Ok, hands up who has forgotten to thread the cable through the sleeve in the top of those orange rubber mains plugs that you used to get from RS before carefully wiring the terminals up? I have lost count of the number of sleeves I have seen cut through by someone who has forgotten and cannot be bothered to take it all apart again. I sometimes solder a banana plug on then remember you have to put the wire through the plastic cap before doing that. BNC plugs are the same. It hasn't improved with age either.
Alan.

LOL. Yes I do that all the time After doing the world's neatest Din plug, do I then find I have forgotten to put the cover on.
I thought I would try to beat Murphy, as now I slip the covers on first and tie knots to stop them coming off. Works very well, as long as you don't put the wrong plug for what ever sleeve or cover happens to be on that end of the cable!