Applying the Art of Electronics (and a hammer) - Page 1
Forum section: electronics / general

author: TerraHertz
author_rank: Super Contributor
timestamp: March 04, 2020, 02:50:06 am
content: 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.

author: james_s
author_rank: Super Contributor
timestamp: March 04, 2020, 06:49:17 am
content: 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.

author: TerraHertz
author_rank: Super Contributor
timestamp: March 04, 2020, 07:51:22 am
content: I'm more interested in the historical development of stuff like this, than actually finding an efficient modern implementation.

author: tautech
author_rank: Super Contributor
timestamp: March 04, 2020, 08:26:50 am
content: Very interesting failure mode indeed.Is it steel ?Could you not just Easyflow weld it with a tiny flame ?

author: TerraHertz
author_rank: Super Contributor
timestamp: March 04, 2020, 09:35:35 am
content: Quote from: tautech on March 04, 2020, 08:26:50 amYeah. 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.QuoteYes, 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.QuoteIf 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.jpgAnd I could re-black the surface after.

author: tautech
author_rank: Super Contributor
timestamp: March 04, 2020, 10:37:02 am
content: Oh, that is a yummy little torch !

author: james_s
author_rank: Super Contributor
timestamp: March 04, 2020, 04:58:34 pm
content: 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.

author: sassywren
author_rank: Contributor
timestamp: March 05, 2020, 04:17:57 am
content: 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?