150W Welding Repair Tool Titanium Plating Lead-Free Solder Pot Adjustable Temperature Tin Furnace with EU plug (WHL #48)

What’s worse than lead-free solder? Lead doped lead-free solder… :roll:

Today’s item is a “500g” solder pot that I bought during the Christmas/annual leave shopping spree mid-December for 12.06 USD including shipping on AliExpress. Prices have even dropped a bit since then.

I’ve always been collecting residue from desoldering stuff as I want to minimize contaminating ordinary trash with lead. Not on a crazy level like the EU tries forcing us to, but if I can avoid PCBs and electronic components getting mixed with domestic waste, I’ll keep them separate. Melting down lead flakes to solid blobs is one part of that, and while it’s of no use for electronics anymore, it’ll still do fine for pouring lead on New Year’s Eve. Which is now forbidden in the EU because dumbfucks might throw their “used” lead into the trash and buy a new set every year. Well, doesn’t really work all that great with wax (their proposed RoHS replacement), does it.

Anyway, I couldn’t resist a soldering pot for 12 dollars, as melting large amounts with an iron or a heat gun is always a hassle. Finally went for it, wasn’t disappointed. A bit Wan Hung Lo construction that needed fixing, but overall it’s doing fine. But first things first.

This was advertised:

And this is how it looks like (after a few hours of operation and some tests at work):

Notice something? Yeah, the “EU plug”. Why shell out money for a full “Schuko” type plug when you only need live and neutral wires, as earthing is for pussies? That’s gotta change.

Other than that, construction is pretty straight forward, a rectangular metal box, one dial for temperature and a mains switch. Even the shitty sticker is as advertised, it doesn’t really stick to the surface all that well. But, and this is the main reason I bought this very unit: The dial GOES UP TO ELEVEN! :grin: How cool is that, seriously…

Disassembly is also pretty easy. The pot itself is surrounded by a square piece of metal, likely to catch drips of molten metal. The inner hole is basically the same size as the outer diameter of the pot, so chances are that won’t help much at all. It looks a bit more like lab equipment that way, and removing it would open up four screw holes on each side, so that’ll stay as it is. It’s held in place by four M3 screws and M4 nuts (for spacing).

The bottom has rubber feet that use the same M3 screws for mounting, someone was thinking about the BOM. Nice. After removing those, the bottom plate pops out and we have full access to the unit.

The pot itself could be replaced, as it is held by two (M5-ish) screws, but it’s not designed for hotswapping. It seems like the heater and the metal bowl are one single unit. I haven’t checked max temperature yet, but guessing from the tempering colors of the bottom of the pot, it could very well reach beyond 400°C. Of course our Chinese friends rated this one to 550°C, not sure about that. Maybe when the flux catches a light?

The controller circuit is highly…optimized. I mean really, have a look at it. I’m thoroughly surprised there’s a fuse in it, but apart from that…one big capacitor, one diode, another diode (could be a diac), two resistors, the potentiometer that pops out the other side, and some three terminal TO-220 thing which most likely is a triac. That’s the most barebone phase cutting circuit one can imagine. Oh, yes, and there’s a wire going to the switch, which is not an SPDT type (despite the three terminals), but it’s a single throw one with button illumination. Not sure if some neon bulb or LED is used, but the excess diode could indicate an LED type.

This also clarifies that the dial is not for setting a temperature. It’s setting a fixed power to the heating element. It’ll eventually settle on one temperature, but it won’t heat up on 100% until that temperature is reached. There’s no point not turning this thing TO ELEVEN and upon melting, dialling down to your desired setting. Lead-free operating temperature is reached at about 6-7, lead-based is about 4-5. 100% / full scale power draw is about 110W at 227V mains voltage (“150W” says the Chinese seller, at 220V AC), and the regulation is pretty linear.

Thing is: The chassis isn’t grounded, and I bet even units with an earthed plug do not have any chassis grounding in place. So that’s gotta change, given the poor general insulation and especially the insulation distance with the wonky PCB mount. Not taking any chances here, this is live equipment.

So after drilling two holes, actually tapping M3 threads into the chassis, removing the paint around them, looking for suitable M3 screws/star washers/nuts, and making a tiny earthing link out of the smallest diameter of green-yellow insulated wire, the unit now looks like this…

You know it’s German over-engineering when your tiniest wire at 0.75mm² area / 1mm diameter is significantly thicker than your 0.6mm (including two layers of paint!) tinfoil bottom “plate” :mrgreen:

Anyway, had fun doing this, now the chassis is grounded in case anything goes wrong, connectors are insulated where possible, mains cable is a tad longer than before (and is now also 0.75mm² instead of 0.5mm²) and the unit is still working.

For testing, I used the current stock of old solder, cooked that crap, poured/separated everything that wants to go fluid from the residue, and reheated. As I’ve tested at work with fresh (lead-free) solder, cables likely want a pinch of flux before being dipped into the molten solder bath.

Please excuse the “Frosty the Snowman” look of these wires, this is due to the mix of lead-free and lead-based solder, which is a terrible mix and should never be used in any application. I know. Still, that’s what I had, and should the need arise, I’ll buy a block of good-ol’ 60-40 that won’t be contaminated with this crap.

Pro tip: Do NOT recycle old solder paste this way, it takes AGES to burn off all that flux and you’ll pollute the entire neighbourhood. If you really want to, heat on a low setting, pour off any flux that now separates from the lead tin balls, stir, repeat. Also do only fill up half of the pot as solder paste pretty much doubles in volume once it reaches that temperature, and an overcooking pot will not pour nicely due to the square metal thing that is in the way.

From left to right (all 4mm² wires): Tinned with 60-40ish fresh stuff with an iron, tinned without flux (don’t!), tinned with gel-based flux, tinned with rosin flux with isopropyl solvent at lowest temperature setting, tinned with the same stuff, but at the same temperature as the others.

All of them have been tinned with the insulation removed for a bit, then stripped after cooldown. You can see how deep they’ve been dipped from the oxide/flux residue rim – and how far the solder has been wicked up beyond that point, which usually isn’t desired. Especially #2 (without flux) has massive amounts of solder wicked up, which is due to longer exposure to the bath, as this wasn’t taking on solder right away. This is getting better with thinner wires, as one rarely does tin 4mm² wires. The rest of them are pretty much equal, so as long as there is some tiny amount of flux, you’re good. And when running proper solder, it’ll look very much like the left one – shiny surface, no lumps, low capillary action (and no burnt insulation).

Nice product, would buy and fix up again. And I think we might get one at work for cable assembly, the time for manual tinning really adds up when you do a few hundred wires in batches. Furthermore, I quite enjoy the fondue-like dipping process and the sizzling :lol:

(Now going back to my biweekly schedule!)


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