menm will 3Dprint you some... ![Clapping :clap:](https://www.eevblog.com/forum/Smileys/default/clap.gif.pagespeed.ce.LImJbaO0yv.gif)
Well the HP 66312A turned up here today.
Bummer: despite what ought to have been reasonable packaging by the seller, Parcelfarce managed to smash the shrouds on the terminals.
![](https://www.eevblog.com/forum/testgear/test-equipment-anonymous-(tea)-group-therapy-thread/?action=dlattach;attach=1154290;image)
I've given it a brief functional checkout and the basics all work. In doing so I discovered an interesting feature, the fan speed is directly proportional to the measured output current (or perhaps power). It doesn't change after a thermal lag, it changes immediately the measured output current changes. Neat.
By the way, this is the heaviest 40W PSU I've ever encountered. In fact, I'd go for it being the heaviest PSU in terms of kg/W that I've ever encountered - excluding PSUs that only put out a 100 mW or so, where they're hitting the limits of how small/light you can practically make something that plugs into the mains.
Edit: Just calculated from the specifications: 4.54 W/kg.
LOL... I could too print something up, pretty quickly. And it would be a lot less assache than tearing that thing down to replace the whole terminal, which I think is necessary on these right? From the photo it looks like the 4mm socket tube is swaged over to keep the nut from being able to be twisted off the terminal.
Exactly the latter. Anyway, if I want it to have a hipster vibe I don't have to go as far as 3D printing, just squeeze a little Sugru onto the retained 'nut' and it's good.
![Smiley :)](https://www.eevblog.com/forum/Smileys/default/xsmiley.gif.pagespeed.ic.R8GFI-pF6f.png)
In all seriousness I might go down that route for a
pro tem solution, which if I do probably means it'll still be there in ten years time.
Yeah, output-wattage-controlled fans seems to be a thing now... even my little Cheap Chinese CC/CV PSU does it.
For sure the opposite end of the spectrum weight/watt wise tho; I've pulled a constant 88 watts out of this little 800 gram toy.
Yes, I know it's a completely different class of machine; more reference standard than PSU. It just made me giggle when you described it in terms of enheavyment. ![Wink ;)](https://www.eevblog.com/forum/Smileys/default/xwink.gif.pagespeed.ic.cldandycH0.png)
Not reference but measurement. The giveaway is that some of the sibling supplies are designated "communications" test supplies; it's all about the fast current measurements so that it can act in place of a battery for mobiles and the like that jump around in power demand.
The current measurement is interesting in itself. The
low bandwidth current measurement is taken in the bog standard method of measuring voltage across a current sense resistor, said signal is also used as feed back for regulation. The
high bandwidth current measurement path is a current transformer in series with the output capacitor (the whole across the output, obviously). So there's quite a bit of awkward fast arithmetic involved in combining the current pull from the supply with the current charge/drain on the output capacitor to get the composite measured figure. Not an obvious choice on the surface, and if I'd come up with the same scheme I'd have wanted to do quite a lot of proving that it could adequately get an accurate output current reading once all the fiddling with number had been done.