YIHUA 850AD Digital Display Hot Air Desoldering Station: Power inlet + power switch retrofit (WHL #85F1)

Small-ish update on the Yihua hot air station: Standby power draw is now zero!

But as is common, things weren’t quite as straight-forward as I had hoped for. Let’s start with a quick teardown of the unit, as promised. The lid is uneventful in that it has the same color on the inside as it does on the outside – and surprise, surprise, the holes go straight through Other than that, most of the chassis space is taken up by the pump, which is very reminiscent of the unit of the Toolcraft hot air station at work, even the sizing of the cable ties. It’s heavily decoupled by rubber baby buggy bumpers popped through the bottom side of the chassis, and boy does it move in operation (at high throughput levels).

In the center there’s a tiny transformer block, so they’re being lazy on their power conversion. Sure, the heater doesn’t care if its AC or DC, and air pumps can probably had in AC and DC versions as well. But the controller board clearly needs a low voltage DC source, so they doing their rectification and smoothing just for the board, on that very board.

The fixed power cable actually goes straight to the board, which is a bit surprising giving the transformer is always on – but I guess it’s easier in terms of cable routing, so whatever. The transformer is then also plugged directly next to it, and so is the heater wiring that goes out to the front. Not sure why one would need tiny extension leads though – did they buy pre-crimped connectors and then mated them to the mains cable (black-blue, red-red)? Anyway, the plastic nut on the fuse holder is another oddball at slightly under 14mm diameter – there’s no exact metric or imperial match, and the applied glue made it a slightly…destructive removal process.

Clearance on the back is actually decent. For me, that means a lot of space to work with; but the unit could be smaller if sized properly. Maybe this is a standard case size, who knows. I wanted to fit a switch, and also the fixed AC cable needed to be changed from its Aussie type to either a Schuko one, or an IEC 60320 C14 inlet, which is by far the most commonly used inlet for Schuko adapter cables.

So, I went to the parts bin and found this: Perfect!

And, as one does, I removed the pump, made a suitably sized hole, and was about to fit it after cleaning up the edges and applying some paint marker for rust protection. End of story, right?


Well…not so fast. You see, I did remove all the wiring from the entire block, because some of the blade terminal connectors were sticking out a bit far, with a risk of touching the insulated, but heavily vibrating pump. Shorter (non-insulated ones) would be a better fit for the side facing the pump. Also, because I cannot remember where the unit came from, I just wanted to check the crimps on the other jumper cables. And on installation (after crimping some new ones)…I bent one of the tabs, and subsequently broke it completely. I never broke spade terminal connectors in my entire life.

I plead “not guilty” though, as even can be seen from eBay photos where this AC-fuse-switch combo block is still offered as new: Those darn tabs of the fuse are significantly thinner than the others (which are regular thickness for flat connectors – probably standardized somewhere). I do not know why one would do that, it’s even more complicated to assemble two different kinds of tabs instead of one proper one, and the proper ones were already on the BOM, so why skimp on two occasions…but they did, and I broke it, and I refuse to buy that crap again knowing it is crap and needs special attention when installing. Yeah, I might now own a hot air station case with a hole too large to fit another switching block, but that’s the price to pay. Seriously, WTF?

Well, it wasn’t so bad, I paid 11.61€ for two slightly different units on eBay, one featuring a large green rocker switch and the other a smaller red one, both illuminated from AC and with the fuse box already fixed to the inputs, no jumper cables needed. While the seller makes wrong sizing claims about the smaller unit, I wanted the larger switch for that unit anyway and the other goes to storage. And the important bit is: It’s larger than the previous one, so I don’t need a super-ugly fix for my case.

One important remark, though: As shown on the fourth image on this post, the case actually does have a cutout for a switch – it’s simply not populated by default and there’s a sticker over it. If one is satisfied with a significantly smaller switch, likely non-illuminated – that’s the way to go, way cheaper and also much easier to install since it’ll just pop in and needs to be wired to the existing AC inlet and the fuse. I decided against it when I found the combo unit in my parts drawer (a mistake in hindsight), and couldn’t go back once I had cut the larger hole for it.

Once the replacement arrived the thing was done and dusted in an hour – crimp a couple of suitable cables, make room for the switch (pro tip: don’t be lazy and use the existing edge of the original inlet – move closer to the side of the chassis, so that there’s more clearance between the wiring and the pump), install switch and pump, and wire it back up. Don’t forget to re-attach the air hose…

A couple cable ties later, this is held nicely away from the pump and the side of the chassis. And in case it does break one day due to coupled vibrations, it’s an easy fix and nothing should go wrong with the heat shrink tubing over it and a properly grounded case with the paint removed from the point of connection (and a serrated washer in between).

So, this is it: (boring black back side, I know)

And this is the thing with power applied, but in full standby – 1.7W of unnecessary power draw. Given the previous reading was 1.4W, this means my indicator uses roughly 0.3W – but that’s a fair price to pay during operation (600W peak power!) , and as a visible reminder to turn it off after use.

Full power off with the new switch: Zero!

Well, looks like I need another post for presenting some temperature data…

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