Applying the Art of Electronics (and a hammer)

[TerraHertz]

A bunch of stuff arrived in two consolidated boxes from the USA yesterday. Included was a HP 37203A HP-IB Extender.
Mainly bought out of curiosity, since it was US $16.40 plus $9.90 domestic post plus very little extra for US to Australia shipping due to consolidation with a bunch of other heavier things.


All went well, except this thing had its rear BNC shoved into the box wall, bending the aluminum rear panel of the instrument.


A purely mechanical fix, but still a practical application of The Art of Electronics.


It just happened to be at hand.  A spacer was needed since I couldn't separate the rear panel from the chassis without desoldering a couple of mains wires, then resoldering and re-shrinkwrapping. Too much trouble. Also I don't have any suitable thick-wall small diameter shrinkwrap tubing.

The bent area included that rivet head, which stands out. Hence the taped-on thin spacer and surface texture protector shim. A bit cut off some old plastic insulator sheet. That rests on the 'anvil', the other side gets hammered.


On reassembly, an unwelcome surprise. One of the HP-IB connector screws sheared off with very little force. Clearly over-tightened in original manufacture. Interesting failure mode.




Now where am I going to get another of those? Does anyone know of a supplier of these very special fasteners? The screws are 3.3mm OD. Seems to be  UNC #6, is that the right name?
Where I can buy say 20 to 100?

Edit: Wait, trying various HP-IB connectors, are there two variants? Old ones using UNC #6, and new ones using M3.5?
Oh great.

Some teardown shots, after reassembly.








Actually at the time I bought it I didn't know you need two of these. I hadn't looked it up, and assumed it would be some kind of signal booster with two HP-IB connectors on the rear. But no, it serializes the HP-IB protocol over a single, duplex coaxial link. With optional twin optical fibre media (not fitted here.)  A manual is on the way, and next time I see one of these really cheap I'll buy this one some company.

[james_s]

A nicely built bit of hardware, although I can see why it was cheap. It's somewhat specialized and rather obsolete now given you can do GPIB over ethernet or WiFi.

[TerraHertz]

I'm more interested in the historical development of stuff like this, than actually finding an efficient modern implementation.

[tautech]

Very interesting failure mode indeed.



Is it steel ?
Could you not just Easyflow weld it with a tiny flame  ?

[TerraHertz]

Very interesting failure mode indeed.

Yeah. I suspect it may have been made from two parts, friction welded together. To reduce wasted metal and machining time in production. Make a lot of the threaded bits from thin rod, and the hollow nut part from fatter rod. In this case the friction weld was botched? It's a remarkably regular tapered shear surface, for a purely strain fail.

Is it steel ?

Yes, in so far as any iron-like substance from China is ever 'steel' as opposed to cheese. Was once washing machines and tin cans, perhaps.

Could you not just Easyflow weld it with a tiny flame  ?

If I can't fairly quickly locate a source of new ones, that's the plan. I do have a tiny oxy-propane torch that works great for stuff like this. http://everist.org/NobLog/pics/20180922/20181013_1413.jpg

And I could re-black the surface after.

[tautech]

Oh, that is a yummy little torch ! 

[james_s]

Actually if it fits together tightly I bet you could bond it with cyanoacrylate, that stuff can be surprisingly strong. If that doesn't hold then brazing would do it.

[sassywren]

If I am not mistaken from that picture the break looks round and conical, a prime candidate for a quick spin weld with a drill?