Author Topic: Someone in 1988 had a boring job...  (Read 5251 times)

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Offline Alex EisenhutTopic starter

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Someone in 1988 had a boring job...
« on: October 12, 2022, 05:51:42 pm »
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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Offline RoGeorge

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Re: Someone in 1988 had a boring job...
« Reply #1 on: October 12, 2022, 06:25:44 pm »
High Voltage pin?
 
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Offline pcprogrammer

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Re: Someone in 1988 had a boring job...
« Reply #2 on: October 12, 2022, 06:34:59 pm »
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 :-//

Offline Jester

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Re: Someone in 1988 had a boring job...
« Reply #3 on: October 12, 2022, 06:37:51 pm »
Looks like a futile attempt to solve a creepage / clearance problem.
 

Online langwadt

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Re: Someone in 1988 had a boring job...
« Reply #4 on: October 12, 2022, 06:39:52 pm »
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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Offline pcprogrammer

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Re: Someone in 1988 had a boring job...
« Reply #5 on: October 12, 2022, 06:50:38 pm »
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.

Offline Alex EisenhutTopic starter

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Re: Someone in 1988 had a boring job...
« Reply #6 on: October 12, 2022, 07:28:29 pm »
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

But still what a boring job "entry-level heat-shrink tube technician" must have been.
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Offline AndyBeez

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Re: Someone in 1988 had a boring job...
« Reply #7 on: October 12, 2022, 08:33:46 pm »
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.
 

Offline james_s

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Re: Someone in 1988 had a boring job...
« Reply #8 on: October 12, 2022, 08:39:14 pm »
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.
 

Offline Bud

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Re: Someone in 1988 had a boring job...
« Reply #9 on: October 12, 2022, 10:54:35 pm »
What is on the mating connector side? Is a wire soldered to it?
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Offline Alex EisenhutTopic starter

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Re: Someone in 1988 had a boring job...
« Reply #10 on: October 13, 2022, 12:02:05 am »
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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Offline austfox

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Re: Someone in 1988 had a boring job...
« Reply #11 on: October 13, 2022, 01:15:20 am »
I'd say to prevent a short when someone is inserting or removing the mounting screw whilst the unit is still powered.
 

Offline Alex EisenhutTopic starter

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Re: Someone in 1988 had a boring job...
« Reply #12 on: October 13, 2022, 01:17:42 am »
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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Offline james_s

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Re: Someone in 1988 had a boring job...
« Reply #13 on: October 13, 2022, 01:44:05 am »
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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Offline VK3DRB

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Re: Someone in 1988 had a boring job...
« Reply #14 on: October 13, 2022, 02:01:51 am »
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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Online fourfathom

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Re: Someone in 1988 had a boring job...
« Reply #15 on: October 13, 2022, 02:10:28 am »
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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Offline Ed.Kloonk

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Re: Someone in 1988 had a boring job...
« Reply #16 on: October 13, 2022, 03:40:04 am »
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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Offline VK3DRB

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Re: Someone in 1988 had a boring job...
« Reply #17 on: October 14, 2022, 06:10:43 am »
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.
 

Online coppercone2

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Re: Someone in 1988 had a boring job...
« Reply #18 on: October 14, 2022, 06:16:00 am »
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.
« Last Edit: October 14, 2022, 06:21:36 am by coppercone2 »
 

Offline eti

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Re: Someone in 1988 had a boring job...
« Reply #19 on: October 14, 2022, 07:47:23 pm »
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
 

Online tom66

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Re: Someone in 1988 had a boring job...
« Reply #20 on: October 14, 2022, 08:27:05 pm »
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.
 

Offline RoGeorge

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Re: Someone in 1988 had a boring job...
« Reply #21 on: October 14, 2022, 08:59:44 pm »
Maybe the shrink tube from that floppy connector has magnetic properties, and it's put there as a ferrite bead.  ;D

Online coppercone2

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Re: Someone in 1988 had a boring job...
« Reply #22 on: October 14, 2022, 09:08:09 pm »
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
 

Offline PlainName

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Re: Someone in 1988 had a boring job...
« Reply #23 on: October 14, 2022, 10:32:41 pm »
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.
 

Offline themadhippy

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Re: Someone in 1988 had a boring job...
« Reply #24 on: October 14, 2022, 10:44:27 pm »
Quote
I'd have a bottle of oil,
duck oil? or at least thats we knew it as
Quote
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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