EEVblog Electronics Community Forum
General => General Technical Chat => Topic started by: Alex Eisenhut on October 12, 2022, 05:51:42 pm
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Why would there be a heat shrink tube over one pin of a right angle pin header?
And what kind of boring job was that??
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High Voltage pin?
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High Voltage pin?
That was what I was thinking too, but the ground plane (what I assume to be the ground plane) is quite close to the pad of that pin. Closer than the pin to the other pins. So yeah who had that boring job and why did they pay for it :-//
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Looks like a futile attempt to solve a creepage / clearance problem.
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to reduce the risk of the hardware going through the mounting hole touching that pin? looks like the other two pins close to the hole and the hole are ground
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to reduce the risk of the hardware going through the mounting hole touching that pin? looks like the other two pins close to the hole and the hole are ground
That sounds like a valid reason. But then in relation to some mechanical movement of what goes in the mounting hole. Because near the PCB if it is some metal stud it could still touch the solder on the pad, when it is a bit wide or shifted to the edge of the hole. Insulation the mounting thing would then still make more sense, and probably easier to do.
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to reduce the risk of the hardware going through the mounting hole touching that pin? looks like the other two pins close to the hole and the hole are ground
This is the header for the heads of a floppy drive. It dawned on me too that the other pins are ground and that mounting hole is pretty close. But the hole is not used in this drive...
This is the Mitsubishi M4851, which is the most highly-engineered 360K 5.25" drive I've ever seen. It has it all. Head loading solenoid, jumpers for every possible variation...
And back in the day floppy drives came with an entire data book!
http://www.primrosebank.net/computers/bbc/drives/Mitsubishi_M4851.pdf (http://www.primrosebank.net/computers/bbc/drives/Mitsubishi_M4851.pdf)
But still what a boring job "entry-level heat-shrink tube technician" must have been.
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Me thinks the EE apprentices were given this as a 'shop task'. Spec read: Insulate Pin 10 to ensure electrode blue smoke protection isolation common mode rejection
The smart apprentice who asked, "why are we putting heat shrink around a pin that's not connected?" was immediately placed on the accelerated path to finding a career with another company.
Someone even more bored had to cut and inspect the length of that heat shrink before it was placed on the line. Wonder if all of the other pins were meant to be shrouded and the BOM was wrong? They just had the one tiny bit to fit.
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Probably because there's a screw hole in close proximity. I would guess that pin is carrying power from a rail that may be able to deliver a significant amount of current, and the screw may be threading into something that is at ground potential.
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What is on the mating connector side? Is a wire soldered to it?
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Just a header thing. But observe the plastic channel for the two cables coming from the heads. This thing's engineering is epic. The PCB even has grid coordinates silkscreened on it, A B C D 1 2 3 4,.
Nuts.
I put a screw with its washer in that formerly empty mounting hole and the washer easily touches the solder fillet. Oh well.
I'm having a great time taking this thing apart, it's so well made! I'm a huge dork for floppies you see.
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I'd say to prevent a short when someone is inserting or removing the mounting screw whilst the unit is still powered.
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I'd say to prevent a short when someone is inserting or removing the mounting screw whilst the unit is still powered.
There is no mounting screw there in the assembly. I just put that screw there to see.
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I'd say to prevent a short when someone is inserting or removing the mounting screw whilst the unit is still powered.
There is no mounting screw there in the assembly. I just put that screw there to see.
That doesn't mean there isn't a mounting screw when that board is used on a different model or revision of drive, or that they weren't planning on putting a screw there. The person laying out the PCB included a hole, they probably assumed it might get a screw.
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Don't know why you infer this boring job is unique. There are many people in the electronics industry with repetitive, boring jobs. There is nothing more boring than staring at solder joints all day, everyday, by quality assurance or process people. Much of the electronics in your home will have parts made by people bored out of their brains.
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But still what a boring job "entry-level heat-shrink tube technician" must have been.
Reminds me of my first real job, where one of the tasks was to put tiny O-rings on plastic air-pump valves. These things were only a few mm's in dia, and everything was drenched in glycerin. I had my face pressed against the magnifier for hours. Eventually I told my boss I was so bored I was going to quit unless he could find something else for me to do. I ended up being shop handyman, driving the boss's Trans-Am around town picking up parts, helping the machinist build fixtures, etc, etc. Way more fun!
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Don't know why you infer this boring job is unique. There are many people in the electronics industry with repetitive, boring jobs. There is nothing more boring than staring at solder joints all day, everyday, by quality assurance or process people. Much of the electronics in your home will have parts made by people bored out of their brains.
I dunno, man.
Going by the quality of some of the solder these days, I suspect inspecting boards would be ever-bewildering if not hysterical.
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Don't know why you infer this boring job is unique. There are many people in the electronics industry with repetitive, boring jobs. There is nothing more boring than staring at solder joints all day, everyday, by quality assurance or process people. Much of the electronics in your home will have parts made by people bored out of their brains.
I dunno, man.
Going by the quality of some of the solder these days, I suspect inspecting boards would be ever-bewildering if not hysterical.
I did it for a week. Super boring, mostly large pin-through hole boards for the PC XT.
But not as boring as when I was at high school when I had a part time job in the Children's Shoes Department at the Myer city department store in Melbourne. I remember I once had to take hundreds of pairs of gumboots out of tight plastic bags (the bags stuck to the gumboots though suction and stiction) and continuously rearrange them on shelves in size order, on a Friday night after school. The boredom was so intense my head was pounding and I had tears in my eyes.
I hated that bloody boring job, but the money was OK. Occasionally the boredom was broken when I had to bring trolley loads of shoes through the Myer Miss Melbourne fashion section which was full of pretty young fashion conscious women. But being so self conscious and socially inept, I always blushed heavily just walking through there. This embarrassment was amplified by an order of magnitude once when a pretty young lady said out aloud to her friend, "Hey, look at his face!" :palm:. Red as a beetroot.
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thats pretty obvious to me, its incase you put too big a screw in there, or someone puts a washer under the screw that is the wrong size and it drifts to the side. how many times do you lose washers and end up with something just a tad too big that you are sure will sit correctly?
I think that's a good design decision. Alot of better boards I see use washers near the screw hole, perhaps there was one originally there and it got taken out with a design change or something. And those kits always get mixed up, with a screw it wont fit, with a washer you need to be on top of your assembly game to catch it. Some board designers are really anal about tolerances.
I recently dropped a washer somewhere for a card and then I got a almost identical replacement for it, but when I did the 'can it short something to chassis test", I ended up on the floor for 20 minutes looking for the original washer. Pretty infuriating but it definitely could have caused a problem.
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As a teenager, one of my jobs on a small production line, was where I'd have a bottle of oil, a 3-pronged expanding plier type tool (spiked prongs) and I'd sit for hours dipping pre-cut rubber sleeves in the oil, sliding them onto the tool, expanding the tool so it stretched the sleeving and sliding wires in. Funnnn. ;D
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You think that's a boring job, I once tore down a Panasonic plasma TV. The drive board had about 30 off IGBTs/MOSFETs on it and damn near every one had a tiny slip-on ferrite bead on its drain/collector.
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Maybe the shrink tube from that floppy connector has magnetic properties, and it's put there as a ferrite bead. ;D
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You think that's a boring job, I once tore down a Panasonic plasma TV. The drive board had about 30 off IGBTs/MOSFETs on it and damn near every one had a tiny slip-on ferrite bead on its drain/collector.
they have applicators for those beads IIRC
Just stick them on a very slightly expanding elastic rod from the back and push them down with a sleeve
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thats pretty obvious to me, its incase you put too big a screw in there, or someone puts a washer under the screw that is the wrong size and it drifts to the side. how many times do you lose washers and end up with something just a tad too big that you are sure will sit correctly?
I think that's a good design decision.
I think it's a poor design - it looks obvious to me that the connector is too close to the hole. Maybe they laid it out then found they had to add the hole right there, because. The sleeve is a hack to cope with that, not a good decision in and of itself.
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I'd have a bottle of oil,
duck oil? or at least thats we knew it as
3-pronged expanding plier type tool (spiked prongs) and I'd sit for hours dipping pre-cut rubber sleeves in the oil, sliding them onto the tool, expanding the tool so it stretched the sleeving and sliding wires in.
pink sleeves ? spent a few months wiring mobile military workshops that used varies multipole connectors and every wire had to have those fitted,along with an id number,you only forgot to add the number or sleeve once,and only discovered you'd forgot it after the final wire was soldered to the connector
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.... you only forgot to add the number or sleeve once,and only discovered you'd forgot it after the final wire was soldered to the connector
That is a bit like always telling others when making cables not to forget to slide the connector cap on before soldering, and what do you do yourself, forget to slide on the cap :palm:
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When you forgot to put a 'revision #' on the silkscreen, so you mark a pin as the rev #?
The idea 'insulate the pin from a screw' doesn't work, since there are two pins with identical spacing from the hole. And the screw/washer would contact the solder fillet anyway.
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Could this be something like the false streets placed in maps to detect plagiarism? Something that has no real purpose placed there. Then in court a counterfeiters inability to explain the purpose would be evidence.
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When you forgot to put a 'revision #' on the silkscreen, so you mark a pin as the rev #?
The idea 'insulate the pin from a screw' doesn't work, since there are two pins with identical spacing from the hole. And the screw/washer would contact the solder fillet anyway.
if you look closely you can see that the other nearby pins are connected to the same ground plane as the mounting hole
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Could this be something like the false streets placed in maps to detect plagiarism?
There's an idea!
Hmmm. Maybe I should say all my mistakes are false streets rather than apologise for the cockups.
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Not as much fun as this guy somewhere in south east asia was having.
I was asked by a nieghbour if I could fix their solar light? As you can see from the image, there was an ingress of water/condensation and, the light was long gone to the great WEEE pile in the sky. Originating from Britain's defunked Poundworld store, it was not made from top quality materials. So why then did someone go to all the trouble of grinding off the chip numbering? From the component layout it's a jellybean solar light chip - like the QX5252. Another identical light was ground in the same way.
Pehaps the IC's were stolen, were on a technology export blacklist or, would be traced back to the slave labor camp were someone is making these for half-a-dime a piece? Whatever, there be a happy man out there ;D
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There's always some idiots out there that think grinding the number off an IC does anything to stop someone from reverse engineering something. I'd probably reverse engineer it and replace the IC out of spite.
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There's always some idiots out there that think grinding the number off an IC does anything to stop someone from reverse engineering something. I'd probably reverse engineer it and replace the IC out of spite.
There is no method for anti-tampering which stops reverse engineering. Grinding numbers off of chips makes enough trouble to stop the only slightly motivated. It may add an increment of cost or time to the cost of copying devices with other means of protection.
Just because you can and have.overcome this method doesn't mean it didn't meet the objectives of the originator. Which might have been something as simple as a few days advantage in time to market
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There is no method for anti-tampering which stops reverse engineering. Grinding numbers off of chips makes enough trouble to stop the only slightly motivated. It may add an increment of cost or time to the cost of copying devices with other means of protection.
Just because you can and have.overcome this method doesn't mean it didn't meet the objectives of the originator. Which might have been something as simple as a few days advantage in time to market
It motivates me to reverse engineer something. On more than one occasion I have taken the effort to reverse engineer a device only because someone had ground the numbers off the ICs, if not for that I wouldn't have bothered but I took it as a challenge. The amount of "protection" that method provides is absolutely trivial, all it really does is make it more difficult for a novice to repair.
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There is no method for anti-tampering which stops reverse engineering. Grinding numbers off of chips makes enough trouble to stop the only slightly motivated. It may add an increment of cost or time to the cost of copying devices with other means of protection.
Just because you can and have.overcome this method doesn't mean it didn't meet the objectives of the originator. Which might have been something as simple as a few days advantage in time to market
It motivates me to reverse engineer something. On more than one occasion I have taken the effort to reverse engineer a device only because someone had ground the numbers off the ICs, if not for that I wouldn't have bothered but I took it as a challenge. The amount of "protection" that method provides is absolutely trivial, all it really does is make it more difficult for a novice to repair.
You have mentioned that a couple of times. Unless you publish your results it is irrelevant to the originators goals. And if it took you more than a few hours to figure out it might have met their goals even if you published. Finally, knowing your proclivities a sophisticated anti-tamper person might strew a few ground chip designs around to distract you from more important and more discretely protected devices.
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I rather doubt the market for garden lights is so fiercely competitive that this has any point whatsoever. All it does in my mind is increase the manufacturing cost by adding another processing step and requiring additional equipment and consumables (grinding wheels, sandpaper, file, whatever they are using).
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Could be just part of The Process. Maybe they make other stuff which is rather more sensitive to being ripped and their in-house process includes removing markings, just like it might also include "bend through-hole leads at 45 degrees".
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You really think producers of cheap tat like this also make anything high end? Colour me sceptical.
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'Sensitive' doesn't have to equate to 'high-end'. And whoever puts that together is probably a contract house who build for many clients. I have no idea if that is the case, but it's not beyond the realms of possibility - guidelines are blindly followed regardless of appropriateness all over the place.
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You really think producers of cheap tat like this also make anything high end? Colour me sceptical.
Industrial espionage, certainly not with this tat; but when you guys now know the PCBs seemed hand soldered, maybe the obscuration was to prevent component theft by the poor bastards who were enslaved on the one dollar and a bowl of rice a day assembly line. This solar light retailed for ONE British pound. How much would that inductor alone cost from Digikey?
As for reverse engineering, it's always a cool mind challenge to discover what parts a manufacturer deemed restricted. But figuring out their motivation is less than clear, even when the part turns out to be nothing more than an obsoleted ST microcontroller. Maybe it's the build customer they're out to deceive when they might have to qualify where their stock came from? It would be very tempting to paint or grind an opamp with a 1990s date code, if it were priced 25 years later.
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You really think producers of cheap tat like this also make anything high end? Colour me sceptical.
Industrial espionage, certainly not with this tat; but when you guys now know the PCBs seemed hand soldered, maybe the obscuration was to prevent component theft by the poor bastards who were enslaved on the one dollar and a bowl of rice a day assembly line. This solar light retailed for ONE British pound. How much would that inductor alone cost from Digikey?
As for reverse engineering, it's always a cool mind challenge to discover what parts a manufacturer deemed restricted. But figuring out their motivation is less than clear, even when the part turns out to be nothing more than an obsoleted ST microcontroller. Maybe it's the build customer they're out to deceive when they might have to qualify where their stock came from? It would be very tempting to paint or grind an opamp with a 1990s date code, if it were priced 25 years later.
That makes a bit more sense.
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You have mentioned that a couple of times. Unless you publish your results it is irrelevant to the originators goals. And if it took you more than a few hours to figure out it might have met their goals even if you published. Finally, knowing your proclivities a sophisticated anti-tamper person might strew a few ground chip designs around to distract you from more important and more discretely protected devices.
I still maintain that it's useless and a complete waste of time, I'm far from the only person who chuckles whenever I open a device and find that the numbers have been ground off the chips. It's a practice I associate with amateurs in China, I've never actually seen it done in anything reputable. It's especially laughable with something trivial like solar garden lights, anyone who can't design the circuit for one of these themselves in a day has no business calling themselves an EE. There are numerous ICs that do the whole thing and the entire circuit can be lifted from the datasheets.
I have seen a clever twist a few times where commodity part numbers were put on custom ROMs in some 70s arcade games, but even then it was obvious from the (published) schematic diagrams that the part was a ROM.
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Haha, LOL:
Some guys rummaged around, in Barney's parts drawer, got some stray circuit board, put a HEAT -SHRINK tube on one of the connector pins...And threw that sucker straight into the 'Engineers Cage'...where those engineers began examining / discussing possible reasons,...reasons WHY ?
Three hours later...
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This thing's engineering is epic. The PCB even has grid coordinates silkscreened on it, A B C D 1 2 3 4,.
Nuts.
Actually that was very usual and is extremely helpful when you look at service manuals or schematics, you can quickly map where is each component/subsystem located.
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And alternatively, passives numbered from top left to bottom right on the schematic(s), with ICs numbered top left to bottom right on the PCB. Reasoning is that ICs are easy to locate on the schematic and passives relatively easy on the PCB because they'll be next to the same IC they are on the schematic. Of course, the trend to have things connected via labels rather than lines on the schematics mitigates against that, now.
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This thing's engineering is epic. The PCB even has grid coordinates silkscreened on it, A B C D 1 2 3 4,.
Nuts.
Actually that was very usual and is extremely helpful when you look at service manuals or schematics, you can quickly map where is each component/subsystem located.
Most of the older arcade games had that. It was practically essential when you had a PCB that was 12"x18" or larger.
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When you forgot to put a 'revision #' on the silkscreen, so you mark a pin as the rev #?
The idea 'insulate the pin from a screw' doesn't work, since there are two pins with identical spacing from the hole. And the screw/washer would contact the solder fillet anyway.
if you look closely you can see that the other nearby pins are connected to the same ground plane as the mounting hole
Could use a non-conductive washer to protect the fillet.
I used to do stuff like this in avionics right out of college. It was boring but not as bad as you'd think. I'd tinker, listen to music and chat with coworkers all day. We'd build 10 to 30 radios at a time and they required a lot of mods and tuning so there was a fair bit of variety. Some higher ups decided it was better to do lots of mods than to go through recertification required for an updated PCB.
Sometimes I put tubes over pins like this but it was on transistors, we'd rearange the pinout and use the tubes to stop the pins from shorting to eachother. We'd also put kapton tape on PCB beside a ceramic cap and then solder 3 caps to it.
Our speed and QA failure rate had a small impact on our wage so that added a bit of entertainment as well.