Crap that is useful: making it less crap

Following on from my previous post, sometimes there are fair reasons to buy crap. Which is fine, as long as you're aware that it's crap. Even then, though, it can be crap in surprising ways…

After hand-soldering tiny 3.2 x 2.5mm crystals in a couple of recent projects (& having to desolder & rework TSSOP-sized opamps to fix a pinout error … grrr, my own fault), I decided I needed a hot air rework tool. Since I'm not planning on using it a lot - I happen to like hand-soldering tiny components under a microscope* - I wasn't particularly interested in spending too much.

Enter the world of cheap and nasty hot air rework stations available on eBay. 57.50 Falling Pacific Pesos later, and I was waiting on AusPost to make me the proud new owner of a "HOTAIR GUN Desoldering Soldering REWORK SMD STATION 3 Nozzles RHOS Yihua 858D OZ".

(Alignment tool, random stuff, Fluke 19, and microwave analyser not included.
May cause death or injury in susceptible individuals or groups.)

Now, before anyone runs out and buys one on my say so (as if!), go read the thread on EEVblog titled "DEADLY WIRING FAULT ; Atten 858D+ Hot Air Rework Station". It's not just about the Atten branded ones; it's applicable to all of the cheap stations like Aoyue, Youyue, Saike, Xpower, WEP, Yihua, etc, etc. And not just minor issues - problems found include mains active wired to the metal barrel of the handpiece…

(Note: if you're looking for a teardown post, this isn't it - but I might do one later. Feel free to read on regardless!)

Truth be told, on eBay they're all likely fakes anyway. Yes, Atten/Yihua/etc make clones of other manufacturer's tools (esp. Hakko), as well as their own range of tools - but they themselves are big enough that others fake them. Even knowing all that, I still bought one. It arrived just in time to heatshrink up the cable I mentioned in my last post…

I'm not stupid though. Before powering it up I figured I'd do at least a rudimentary check for the known faults, just to make sure my first experience wouldn't be my last.

• Earth pin to case: <0.2Ω. OK.
• Earth pin to handle tip: ~6Ω. Not great, but the same as others have reported. I'll try not to lick the barrel while it's on...
• Active fused?: Rather than pull it apart, I opened up the fuseholder. Active connected to the sleeve of the fuseholder. The fuseholder was the safety type with the sleeve recessed far enough that curious little fingers can't contact it, so that's fair enough. So far, so good.

Replacing the fuseholder cap, it seemed to jump the thread when barely finger-tight, but was otherwise holding OK. Now to turn it on...

Totally dead. Damn. Now I've got to open it up…

What's that wire floating around there, with the bare metal tag on the end? That's not coming from the power lead, is it? It's not the active, is it?! Yup…

Turns out what I thought was jumping the thread when I replaced the fuse was the fuseholder breaking. It looks like the threaded 'sleeve' part of the fusholder, which contacts the fuseholder cap to connect the top end of the fuse, broke from the solder terminal & pulled straight out of the fuseholder body. The only things holding it in were the springy-ness of the metal (plated brass? copper?), the tiny millimetre-wide neck that connected it to the wire terminal, and luck:

Clockwise from top: fuseholder body, fuseholder cap, internal sleeve,
broken-off tab, and a random broken SMD capacitor from the dust on my
workbench. It's probably an 0805...

Now I don't recall that particular fault being mentioned anywhere. Another one to watch out for…

In fact I wouldn't mind betting that it's been a systemic assembly problem in the past. I forgot to take pictures before removing the fuseholder, so what you don't see above is that the brown 'snot' used to secure the mounting nut was also applied around the base of the broken terminal. I suspect that in the past the crappy fuseholders used have broken during assembly (causing 'Chinese QC Failures' a.k.a. DOA returns), and the snot on the terminal is an attempt to prevent that.

What's a man to do? Well, since I wanted to finish off the audio cable I simply soldered the two wires from the fusholder together - using the tool itself to shrink some heatshrink over the joint ;) - and carried on. I don't recommend that though…

So later on I made yet another trip back to the sex-toy shop, where their M205 fuseholders come in two versions:

• The dangerous one, where you can touch the internal metal sleeve with your finger when the cap is removed, and
• The 'safety' fuseholder - which IRL looks just as crappy as the one that broke.

Needless to say, I bought the dangerous one - I've already got a crappy one, even if it is broken! - and I needed something to get by until I can thow a proper part into my next E14 order.

Just to explain my point about it being dangerous, here's a pic:

On the left is the broken original fuseholder, which I've re-assembled. On the right is the replacement I bought. In the broken fuseholder, notice that you can barely see the edge of the sleeve contact? I had to angle the light and turn the flash on just to get that much of it; it's well down in there and mostly safe from fingers, test or otherwise. On the replacement, though, I can touch the sleeve with even my fat fingers...

(Yes, I've heard all the arguments about how it's perfectly safe if it's all wired correctly, or you're careful with this, or you do that. Question: are you willing to bet your life or anyone else's on everything always being wired and handled correctly? Just spend the extra pennies to buy a f...ing decent-quality standards-compliant safety fuseholder and be done with it...)

Coming soon: the mysteries of crimp SMA connectors. Why are the ones for cheap RG58 cable so expensive, while the ones for expensive RG174 cable so cheap?

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(* I spent a big part of my degree peering down a microscope finding, counting, & occasionally dissecting very tiny things. I think it affected my brain…)