32
Condor
68d

This Chinesium power supply looks disgusting 😷 I have no idea what shit this manufacturer put their hands into when they built this piece of garbage (that nonetheless works without blowing up, go figure) but it's all sticky 😐 I want to clean it up before putting it into a new enclosure, but I don't have an ultrasonic cleaner and don't really feel like desoldering all the components and giving it a washing. Are there any other cleaning options that are inexpensive and don't damage the components or the solder joints? Pure alcohol perhaps?

Comments
  • 5
  • 5
    The schmoo is difficult to see on the original picture, but here's a close-up.. my guess is that it's coffee or something like that?
  • 2
    OMG...

    hope you gave it a 1-star rating.

    I don't know any good method ... maybe that new toy for kids, the sticky stuff. It was first invented to clean workbenches.

    I buy them at the local Chinese store, but I just found it on Aliexpress:

    https://aliexpress.com/item/...

    Btw I paid 3€ for 12 packs, I don't know if the price is 1.5€ for 1 pack or 12... If for 12 is cheap, if for 1 (I think it's only one package ) Is very expensive in Aliexpress.

    Anyhow, if you have a Chinese store close to you, you will probably find it.

    It's perfect to clean anything, except cardboard and cloth...
  • 6
    Could it be flzx residue from wave soldering? I don't know how much that generally is, because those boards usually get cleaned…

    Apart from the main transformer, the voltage set trimmer and the input voltage selection switch all components should be washable. If you desolder these, you can dump the whole thing into IPA or ethanol. Not getting any into the transformer is important, because the dirt will get stuck there and ruin your insulation distances (assumung there are any to begin with).

    Was the price really worth it? Cheap power supplies are always a fire and a safety hazard. The PCB looks like they halfway copied another design (notice the logo resembling Mean Well) and played the game of “Let's find out which components we can remove with the power supply still working under normal conditions” for a while.
  • 4
    I'd still be interested what those sloppy extra windings on the output filter choke are for, though.
  • 4
    @GyroGearloose Thanks, will buy some later :)

    I didn't notice the stains when I gave the rating, only the improperly wound choke. 4 stars I gave it. But given the amount of work I have on this crap, I'd totally revisit that and give it 1 star if at all possible. I ended up starting the full desoldering process by the way.. sucks big time, especially when during your component photoshoot (for placing them back properly afterwards) your Nexus phone craps out as usual.. Huawei, how difficult can it be to contain the angry pixies in a fucking lithium cell, seriously.. fack!
  • 2
    @Condor lol next time buy a Xioami Mi A1 or A2.

    Only recommend those ones from Xioami because they have Android One, no bloatware.
  • 5
    @7400 Not worth it, but I couldn't go any higher without risking significant customs charges.. anything over €22 is charged for by customs, for their "duties". Which are usually more than the product itself. Not sure if it's flux from wave soldering, as I've never seen it as residue on a PCB before. The main transformer I'm currently desoldering, quite the chore actually. The caps, switch (I'll just bridge those holes to 220V side later I guess) and some of those triacs on the side are already gone. Trim pot I still have to do, and some others that I'd like to place a little bit better into the PCB. Anyway, guess I'll pay a visit to the pharmacist for some ethanol then. Thanks for the suggestion!
  • 4
    @Condor at work, we have PCB cleaner like that stuff here, spray bottle with brush: https://conrad.com/ce/en/...

    Works also for whiteboards when the writing is so dried up that regular cleaner fails.
  • 4
    Well, you don't have to buy from china, do you?
  • 5
    @Fast-Nop: I like that stuff a lot. But in the end, it's just a pressurised container with isopropyl alcohol and a brush.
  • 4
    @7400 No idea if there's any local stores that sell this stuff (that doesn't cost me an arm and a leg), so I always end up in the Chinese stores for power supplies ¯\_(ツ)_/¯ maybe I'll reverse engineer one or look for schematics online and build my own in the future. Except for the transformer, the components shouldn't be too expensive and difficult to source anyway.
  • 4
    @7400 it doesn't smell like pure isopronal, though. It smells way more interesting. :-)
  • 1
    Water and soap does wonders.
  • 5
    At work, I also use the product @Fast-Nop brought up.

    Other than that, I use Isopropyl alcohol applied with an old toothbrus, if necessary.
  • 4
    @Codex404 water damages the solder connections and the copper traces, and soap even more so. That's the reason - after excessive shorting when introduced during operation, as soapy water is a relatively low impedance path - that introducing water to electronics is strongly discouraged. Even distilled water which is a pretty good insulator is often discouraged because the introduction of even a tiny amount of impurities makes it a low impedance path for electricity to flow through.

    I ended up buying some IPA 🙂 but I'm pretty sure that the apothecary ripped me off.. I bought 500ml and the bottle that she gave me is 200ml at best 😐
  • 5
    @Condor and even distilled water still has its high dielectric constant of around 80. For DC, this doesn't matter, but for AC, that will work like an undesired capacitor between anything and anything else.
  • 6
    @Fast-Nop interesting, I didn't know that! Out of curiosity, what would be the ballpark capacitance range of a small pond of distilled water? Probably it depends on distance between the probes and voltage and things like that, but what would we be talking about, pF, nF, maybe even into the uF range?
  • 3
    Well, there is some stuff you can buy from China, other stuff... Not really.

    Arduino stuff is very cost effective and pays for itself, Most electronics suck. If the branded version is double the price, better buy from a brand, if it's 5x or 10x, buy from China. Except for very specific stuff.

    For example, a Raspberry pie here costs just a little more than from China, so it's better to buy at the local store, on the other hand, an Arduino Uno goes for 30€ and you can get one for 3€ or 4€ that is good enough...
  • 4
    @Condor ah, I thought you just wanted it clean in the case. But it also has to work, then water and soap isnt a good idea indeed 😏
  • 5
    @Condor If we assume two parallel conductors in air, length 10 cm, distance 1 mm, that would be about 1 pF. If we replaced the whole air with destilled water, that would become 80 pF. But if we only place water in-between, the factor will be less than that. However, the field lines get "sucked" into the more permissive medium, which concentrates them, and in-between is the hottest spot anyway. My guess would be perhaps 40 pF.
  • 4
    @Condor But that isn't even the worst. If it's some kind of HF mainboard, then the wires aren't just wires anymore, but become distributed lines. An impedance change somwhere in the middle can cause impedance mismatch, causing reflections. With 500 MHz, the wavelength would be 60 cm. Usually, any kind of such aspects can be ignored when the system is small compared to the wavelength, which engineers quantify as a factor of 10.

    But that would be only 6 cm, so mainboards are designed with HF in mind. Especially because PCs work with rectangular signals where quite some harmonics in frequency domain are needed to give them a proper shape in time domain.
  • 5
    Don't undererstimate water as a solvent. There are people cleaning old Tektronix scopes by putting them in a dishwasher. If you remove the components which tend to suck up the water (transformers, super high impedance stuff, maybe pots), and let it dry long enough, it isn't that big of an issue.
  • 5
    @Condor
    Propably flux, very shitty flux.

    Tell us more about that gunk.
    I think even resin isnt that bad/messy as that thing on the pic.
  • 6
    @Fast-Nop Thanks a lot for the explanation! 40-80pF doesn't sound like much, but it could impose real problems in a circuit indeed. Probably best to not submerge a HF circuit in distilled water for improved cooling performance then :P

    @7400 Doesn't that damage the solder joints though? And the copper, it'd rust, wouldn't it? And doing that with a Tektronix of all things.. those things are super high end O.O

    @Gregozor2121 It looks like it's crappy flux yes. Resin could be the case as well - it's got that dark tint to it - but how would that accumulate on the top side of a THT circuit? That said, flux shouldn't accumulate on the top of a board either.. but whatever it is, I can't seem to get it all off without desoldering the whole damn thing. If I wanted to do that, I'd have a PCB house make the PCB and assemble it myself. Maybe I'll take it as an opportunity to get a schematic and PCB layout out of this thing, then I can make a bunch of them in the future :3
  • 4
    @Condor: The trick is to keep it powered off while there's still water present. The corrosion is primarily electrochemically caused. Here's a (German, sadly) repair story, where someone showered the scope mainframe and let it dry for 14 days: https://amplifier.cd/Test_Equipment...
  • 4
    @Fast-Nop Faster. PCB cleaner, all the way. Really useful as a general purpose cleaner too. It removes everything.
  • 4
    I stand corrected. I didn't check far enough into the safety datasheet and while IPA makes up the majoruty of Kontakt LR, there are more solvents in there. Explains why it's working better than plain IPA.
  • 2
    @Condor and let's not forget the charges bPost asks you for doing all that awful work of giving your package to customs!
  • 3
    @epse they don't just charge for awful work at customs.. they charge for awful work on everything 🙃 slow service at post offices, extremely unfriendly personnel, ... Almost like De Lijn :')
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