I have just done something that I have to post here.
It was 11 am and I am in good shape mentally and physically. I have an HP Pavilion dv9000. The power supply was stolen by a worker (along with two other old laptops). I tried to get a replacement, and even ordered one. When it was delivered, the plug was not the right size. I could not see a proper replacement on the internet. These things are very badly specified. An after-thought.
OK I know that is false. I order spares all the time and I know that if you hand over the correct spec, you get the right part. So, either you ordered the wrong thing, or you made this up.
I saw a universal power supply at the hardware store and bought it. 100W with output switchable from 12, 15, 16, 18, 19, 22 and 24 volts - and a 5vdc USB port. The input was 110 vac to 240 vac and also 12 vdc from a car lighter socket. It had 8 different adapters.
Those are OTC items and common as muck. In fact, I have two and there is no "switching" involved in them. One merely plugs them in and they automagically work out the input and output voltage required. It is a long time since I have even seen one with a manual selector.
So I tried the one that seem to be the right fit. The last thing I wanted was to break anything. I took the adapter out of the rubber holder and I was very happy that it fit relatively easily. I tried it two more times because I wanted to see if I could sense the fit of the inner pin. I also rocked to slightly and gently to feel the fit. Great.
OK you are having a giraffe, now.
I then assembled the adapter on the power supply, selected the correct voltage and then tested the adapter from voltage and for polarity with a voltmeter. All good.
Assembled? Seriously?
These devices are simple. Simply select the appropriate adapter from the selection provided and attach it to the end of the wire. One can hardly call that "assembly" unless one has a rather quixotic definition. "Plug it in" hardly seems like "assembly" does it?
And then the adapter would not fit.
Right, so you picked the wrong one. Go back and pick the correct one. These devices are supplied with DOCUMENTATION for that very purpose.
But no...
It seemed oversized. I went and got a set of drills and my vernier.
You went for a set of drills????????
The inner pin was the the size of a 1/16inch drill bit. The outer sleeve of the adapter was 5.45 mm. The laptop socket sleeve was 4.95 mm.
How an earth did I fit a 5.54 mm plug into a 4.95mm hole?
Let me guess, you used a hammer.
It is possible the hole itself is 5.5 mm and the metal contact fingers are slightly less. I tapered the plastic on the adapter to see if that would help. But it seemed clear that the metal insert in the laptop is 4.95 mm. I have a 5.45 mm metal adapter hitting the 4.95 metal sleeve on the laptop.
Yup, you used a hammer.
By filing it you potentially shorted out the PSU and totally invalidated any warranty you may have had.
Even pressing the vernier hard got me to 5.0 mm in any position.
Because you were using the wrong one. What part of this is challenging for you?
My initial feeling was that I was hallucinating. But I know what I did. And I took it slow and carefully. Is this a glitch in reality?
No this is an example of borking a simple task comprehensively.
So ironic that I have said that posters here are trying to fit a square peg in a round hole and here I fit an larger round peg in a smaller round hole. I thought about temperature difference but it would not accommodate such a difference. Besides both were in the study the whole time.
You picked the wrong terminator. Why can you not admit this?
I can just imagine the responses. I can assure you it is not me messing with you. It might be God.
Or it might be a failure of the RTFM procedure.
Look, I will make it easy for you. I have had...must be hundreds of these replacement PSUs through my hands at this point. It is a trivially easy task. I actually keep the superfluous adapters as spares. Seems odd, but has saved many a sinking laptop. All that has happened is that you picked the wrong adaptor, but rather than admit an error, you tried to force it to fit.
BY FILING IT DOWN.
Also, for some reason, you used a vernier. Why? These devices, even the one supplied with the laptop in the first place rely for their correct operation upon a ton of wiggle room. Precision is irrelevant and I have no idea why you think it does.
So some explanation.
The plug that goes from the PSU to your laptop (or any device, really) is cylindrical, a shiny metal cylinder. Actually it is two concentric metal cylinders separated by an insulator. One cylinder is positive, the other negative.
The socket on your device is the reverse. It has a central pillar (intended to contact the inner cylinder of the plug) and a spring contact intended to contact the outer cylinder of the plug.
Notice I said "spring". The outer contact of the socket is sprung so that it forces the inner cylinder of the plug to contact the inner pillar of the socket.
Anyone with a laptop can verify this right now simply by looking carefully at both plug and socket. In the socket, one will clearly see the pillar, and the outer spring contact. In the plug one will clearly see the concentric cylinders separated by an insulator. Usually black, sometimes blue, occasionally red.
For this to work, the plug MUST be smaller than the hole in the case of the device (not the socket itself) to allow that spring action to occur.
It is awfully common for a "customer" to select the adaptor that most tightly fits the hole in the chassis while not understanding that the slack is the very reasons it works at all. If one does that, then the socket pillar cannot contact the inner cylinder and nothing will happen. Rarely have I encountered someone filing it down to fit or similar. But it does generate some humour whenever it happens.
ETA: Since you claim to be an engineer of some sort, why is this a mystery to you?