Making a Handskit hot air station a bit less stupid

[spleenharvester]

I bought one of these as it was the only one I could find that is compact enough to fit in my toolbox (though I've since found KSGER make a substantially safer looking one). It's one of those fan-in-handle things that has the 230V element in the handle. Quecoo briefly sold a similar unit but discontinued it.. maybe they couldn't find solutions to these problems. I'm aware these fan-in-handle things are garbage compared to a good air pump station but I only really use this for occasional QFN work etc.

I did not realise at the time of buying that its design is... interesting, to say the least. The shithousery is covered pretty extensively in this thread on EEVBlog.

• The case and handle of the hot air gun are both unearthed, and the earth pin on the 230V kettle lead input is not actually attached to anything (even though bizarrely there are several connections and markings for it on the PCB - none of these go anywhere either). The seller made some rather amusing attempts at bullshitting the OOP into thinking it's grounded. Why are these manufacturers all so allergic to earth wires?
• The earth lead passes within 2mm of the live track on the power supply
• The front panel 8-pin GX12 connection for the hot air gun exposes fused live 230V to the user if unplugged during use
• It's only fused on the live side so if your plug is 2-pin there's a 50/50 chance of getting unfused live on the output
• No anti-creep plastic between the PSU board and the case

Here's the unmodified internals of mine, it's changed a bit from the original design shown on EEVBlog but very similar and still has the same problems.

• Problem #1 was relatively easy to fix by running an earth wire from the earth pin on the handle to the earth lead on the 3-pin plug, and from there onto the case.
• Problem #2 was also easy to fix by just desoldering the earth lead from the power supply board, seeing as it doesn't actually connect to anything on it at all. Not sure if any other points on the power supply board need grounding?
• Problem #3 there's no way to make it safe without removing that connector entirely and hard-wiring it in like a lot of other stations do (like the KSGER), so I have opted to just lock the connection with threadlocker to prevent it being exposed. Looks like the Quecoo had the same thing and possibly that's why it was discontinued? Fortunately the live pin is in the middle so I don't think there's a risk of it shorting to the connector housing.
• Problem #4 fortunately does not apply to me as in the UK we have non-reversible 3-pin kettle leads.
• Problem #5 was also easy to fix.

Unless I'm mistaken I think the station is now relatively safe to use, though if anyone could check my logic I'd appreciate it. The problem I'm having now is that the thermocouple readings randomly go nuts. Sometimes it will have a nice stable temperature, other times the reading constantly wildly oscilates between 100*C and 500*C. It stops freaking out like this sometimes if I pick up the handle and shake it a bit. Any ideas what I need to change, some sort of cap or pullup resistor missing somewhere? Here's a close up of the control board. Any other ideas on how to improve this thing appreciated. I suppose I should probably ground the outer metal of the 8 pin GX12 connector itself?

The one thing it seems to have going for it is it seems to have a legit STM32, not a clone. Though I have no idea what firmware it is running on.

[stj]

the mains on the GX12 was common in the early stations.
i have no problem with that as such - people using these things should know better than touching it and you can do more damage to yourself with the heat.
what i dont like is GX12 isnt rated for those voltages and they dont have enough distance between the contacts.

as for earthing, it's lazyness.
china and much of asia including japan dont always have any earthing in the buildings.
does the middle east have earthing? the ground is so dry i cant see how they can easily do it!

[stj]

i see on EEV somebody asked about "PAT class"
it doesnt fall under PAT because it's not considered "portable" and it has a remveable cable anyway.
if it was portanble only the cable would need to be inspected together with a visial damage check on the inlet.

there's a whole scam industry evolved around pat testing!

[spleenharvester]

Lol this piece of garbage made it a whole 3 uses before blowing the element. I need it to limp along another few months til I can afford to replace it with one of the nice KSGER ones. The station is 700W, do I need to replace it with another 700W element or is there any benefit to replacing it with a higher wattage one? Also what's the insulation material, I'm guessing some sort of fiberglass? (E: It's mica paper, probably why my hands are so itchy now lol)

[stj]

even if the element shorted to ground it wouldnt blow,
last time this happened on a forum it was suspected that the guy had been given a 110v element in a 230v unit!
i have been using a fan-in-handle unit for years without issues.
the heater is the same as the pump-style ones,
only the air source is different - and the pumps do fail - probably more than the fans that are similar to ones in laptops
i had a pump style one first - until the pump failed.

[spleenharvester]

even if the element shorted to ground it wouldnt blow,
last time this happened on a forum it was suspected that the guy had been given a 110v element in a 230v unit!
i have been using a fan-in-handle unit for years without issues.
the heater is the same as the pump-style ones,
only the air source is different - and the pumps do fail - probably more than the fans that are similar to ones in laptops
i had a pump style one first - until the pump failed.

Ah ok cool, that would make sense - I found a sturdier looking and 220v element so hopefully that will work. The soldering in this handle is piss poor though, going to rework that too.

[stj]

i'v seen the entire hand pieces sold for under £5