Apologies for this necro post (I only bought mine a week ago from Banggood - primarily for the hot air reworking feature). I'm adding my own observations here to alert anyone reading this topic as a result of a google or DDG search, to the presence of mains voltage on the pins in the "
male" panel sockets on the base unit.
I'd opened the control unit up to do a safety inspection and everything seemed to be ok. It was only when I tested the contact connections in the female plug to check the ESD earth continuity and the resistance of the iron's heater element that it occurred to me to check the level of the voltage being sent to the pins.
It was the fact that the cold resistance was not the expected 8 to 10 ohms that I'm used to seeing with properly designed soldering stations but 133 ohms which would require 100v rms or more to generate the typical 70 watts or so of heating power. Testing with a DMM revealed the presence of the full 240vac of my mains supply voltage with the iron unplugged.
Since this cheap soldering iron/hot air soldering station lacks any form of documentation to advise against plugging and unplugging the iron and hot air wand whilst it is switched on and the need to fit the rubber "dust covers" to any vacant female panel socket (typically the iron for those who bought it as a cheap hot air soldering reworking station - the iron is pretty naff). I thought, unlike the countless youtube reviewers, that this glaring electrocution hazard should be highlighted to warn anyone who mat not have realised the true significance of the rather fanciful lightning symbol embossed on those attached rubber "dust caps" which appear to have been attached as an "afterthought" to mitigate against the use of a male connector carrying full mains voltage contrary to common safety practice.
This use of a male panel connector isn't a safety issue with low voltage irons using a mains isolated 20 to 30 vdc supply to power an 8 ohm heating element but when it comes to mains voltage power, it's a definite no no. Ideally, the gender of the connectors should have been reversed in this case rather than apply a sticking plaster solution of a black protective rubber dustcap embossed with a lightning flash providing the only hint of the potential hazard of an empty socket.
For those curious about how the iron is temperature regulated, this seems to rely on the heating element having a pronounced positive temperature coefficient (133 ohms at 24*C versus around 500 ohms at 500*C. Standard heating element wire has a very small tempco from cold to bright red heat temperature (around a 10% increase from 25 to 600 *C). There was definitely no indication that a thermo-couple had been incorporated into the heater circuit (less than 0.1mV after setting it to 500*C and swiftly unplugging it to test for the presence of any Seebeck voltage effect.
The temperature control does work surprisingly well considering the change of resistance measurement method used to sense this. However, the iron does take a couple of minutes from cold to stabilise within +/-5*C of a steady tip temperature.
In my case (and that of most reviewers) this was some 20 to 30 *C above the set point. Since it allows the end user to calibrate this offset out (undocumented, of course!), this isn't a huge problem but it's the very sluggish response that will prove the most irritating shortcoming to many, if not all users.
Although I'm rather tempted to throw the iron into the trash and disconnect its front panel socket to render it a little less hazardous, I've decided simply to set it aside for use as an emergency 'backup' and to provide additional heating when dealing with large thermal mass joints and to make sure to keep the 'dust cap' in place at all times and avoid switching on the soldering section.
The hot air wand socket suffers the same hazard but since there's normally no need to unplug this from the controller, the electrocution risk remains acceptably small (at least as far as competent adult usage is concerned). The temperature control on the hot air appears to function ok as far as I can tell.
I checked this with a Metrawatt analogue wattmeter on my 240v mains and it limits demand to a maximum of 700W during its initial warm up before dropping down to stabilise the temperature. At a setting 350 *C and maximum fan speed with the largest nozzle it averaged around 220W, dropping to 180W with the medium nozzle and 120W with the small nozzle, confirming that some form of temperature control is being used.
The cool down process takes about a minute with the largest nozzle, taking some three minutes or so with the smallest before dropping to the 100 *C mark that starts the over run timer that triggers the delayed power down. If you have suitable silicone oven mitts (I use two - one inside the other), it is possible to safely swap out nozzles (but it does require a bit of careful wriggling to separate them from the business end of the gun). If you don't have such heat protective handwear, you'll have to allow another ten minutes of cool down time or else use a pair of long nose pliars if you really can't wait (not a recommended solution since it risks damaging the nozzle).
I haven't tested the hot air wand with actual reworking tasks yet so can't offer any personal opinion on this aspect of its performance. Using hot air to reflow solder smd components is more of an art than an exact science anyway so I won't be able to offer any opinion until I've acquired the requisite experience.
However, since I know the wattage and the effect of what seem to be a common range of nozzle sizes, I expect it will prove to be equally effective as any similarly rated hot air soldering wand anyway. I've got plenty of scrapped boards in my collection of salvage to practice on so it's just a matter time before I can safely risk reworking kit I care about.