GJ-8018LCD: a basic hot air gun and a brief comparison

I often use a soldering station with a hot air gun in my work. But since the station is quite bulky and lately I've only been using its hot air gun, I decided to replace it with a standalone hot air gun, so to speak.
Inspection, teardown, comparison—business as usual.

As I mentioned at the beginning, my goal was to get the large soldering station off my desk.
But I also had a second goal: to try using a hot air gun with a fan instead of a compressor. I'd read reviews of this model and even asked in the comments how convenient it was to use, but as they say, you never know until you try it yourself.
I was especially interested in comparing it with a hot air gun that uses a compressor rather than a simple fan to move the air.

This won't be a very long review; there's not much to say about it, but I'll start in the usual way.
The hot air gun arrived in a white envelope. I don't know how they managed to squeeze it in there, but it was packed tightly.
The packaging wasn't damaged at all, and the hot air gun itself was tightly wrapped in plenty of bubble wrap.


As usual, a quick look at what's included.
The package includes:
1. Hot air gun
2. Four nozzles with different diameters
3. Stand
4. Manual.


The manual is quite long, but essentially useless—at the very least because it's in Chinese and English, and at most because who reads manuals anyway?


The accessories were packed in plastic bags from the start and arrived undamaged.


The stand is a little puzzling: it has four holes for some reason, each with a washer welded on. But it turned out to be quite handy after all—fairly stable, and the hot air gun sits snugly on it. So it'll come in useful.


The package included four nozzles with diameters of 3, 5, 8, and 10 mm.
A quick aside here. In my day-to-day work, I usually use just one nozzle—the 5 mm one, since it's the most versatile—so I used only that one for all the tests below.
The 8 and 10 mm nozzles are usually too large for my work, while the 3 mm one is too narrow, especially for this hot air gun (I'll explain why later).
I really should buy some specialized nozzles sometime, but I keep forgetting. I'd like one with a square opening to match the pin layout of ICs.


The first thing I want to point out is that this hot air gun is big. That's understandable, since it contains not just a fan but also electronics and a display. Still, it's unusually large.
I was pleased to see that the power cord has a European plug, so there's no need for an adapter or to replace the plug.


Here it is next to my old hot air gun for comparison. The new one does have an advantage, though. The old one has a fairly thick air hose, with wires running inside it to the heating element and sensor, which makes the whole setup rigid.
The new one is more mobile in that respect, especially since it isn't tied to a station: just plug it into an outlet and use it. That's why I bought it.


You can use the hot air gun perfectly well without a nozzle, especially since it has a pretty decent airflow in this mode, thanks to its fan-based design.
This photo was taken before the burn-in, so it still looks nice here. The coating darkens over time.


The handle has a temperature display, a power switch, two knobs for adjusting the heater power and airflow, and a heater-on indicator.
You can see an extra soft ring on the left. It turned out to be quite handy. The fan inevitably causes vibration while running, and this shock absorber noticeably reduces it.
Compressor-type hot air guns don't have anything like this, since there's nothing inside them but the heater and temperature sensor.


Air is drawn in from the back. The openings seem a bit small to me.


First, I checked how much power the hot air gun draws in different modes.
1. Heater off, fan at minimum speed
2. Heater on, fan at full speed.
3. Heater at about half power, fan at full speed.
4. Heater and fan at full power. As they say, where are my 17 years 450 W?


To take it apart further, remove the two adjustment knobs, undo the two screws at the back, then undo another pair of screws securing the power cord.
The circuit board is reasonably neat, though the soldering is a bit rough, and they clearly didn't bother cleaning off the flux residue. Still, it could be much worse—and it could be better, too.
It was immediately clear that the display is just a separate device that adds only a little functionality.


Undo a couple more small screws and take out the main board. The circuit looks large and complicated, but a closer look showed it was as simple as a house corner.
On the left and in the middle are the power supply for the fan and thermometer. On the right, you can see a small heatsink with the fan speed control circuit's regulator mounted on it, and the heater power control triac above it.
The voltage at the fan terminals at maximum speed is 15 V.


Here you can see that the digital display is nothing more than a thermometer.
Two wires supply power, and the other two go to the thermocouple, so there's no temperature regulation at all.
The transformer, on the other hand, is quite large—more than enough to power a small fan.
In ordinary hot air guns, the motor is often simply connected in series with the heater. But models with separate speed control and a cold-air mode have a small power supply like this one to power the fan.


Unable to find a schematic for this hot air gun online, I had to draw one myself.
The component designators may differ slightly from the actual ones, but that doesn't really matter, since the circuit is very simple and it's easy to find the component you need.
The schematic clearly shows several main sections:
1. The power supply itself, a conventional self-oscillating converter.
2. The fan speed control, built around an LM317 regulator.
3. The thermometer power supply, implemented as a parametric regulator consisting of a resistor, Zener diode, and capacitor.
4. The heater power controller, consisting of a triac, diac, and a trimmer resistor with a capacitor.

There's no point in dwelling on the power supply; it's all simple and straightforward. But I'll spend a little time on the heater power controller.
The heater's measured resistance when cold is 103 Ω, which gives us about 465 W at 220 V, or as much as 510 W at 230 V.
But hold on—we measured only about 250 W above. Where did the rest go? Here's why.
The circuit includes a power limit in the form of resistor R10, connected in series with the variable resistor. This limits the power to about 50% of the maximum. There's also a small catch: adjustment starts at about 25% of the variable resistor's travel.
So what does this mean? You can easily get more power—even the full 465 W—but the designers apparently decided to play it safe, since this is a soldering hot air gun and it's sometimes used with nozzles that restrict airflow, and there's no temperature control.
If you use the hot air gun without nozzles, you can reduce this resistor to 150–220 kΩ. Don't go lower, or you won't be able to set the power to zero.
To get the full adjustment range, remove R10 and install a variable resistor rated at around 680 kΩ or higher.


The motor is a standard brushed type, nothing special. But to reduce interference from brush sparking, a capacitor has been added directly across the motor terminals.


The fan impeller.
I described the downside of this type of system above: the fan simply can't generate enough pressure to push air through narrow nozzles.
On the other hand, this system is more efficient at higher airflow rates.


The heater is completely standard, like those in other hot air guns: nichrome wire. There's a thermocouple at the end. It looks a little odd, though—there's usually a bead there, but here it looks as if the bead has broken off. Still, it works.


The heater and thermocouple are connected via a plug, but no matter how hard I tried, I couldn't disconnect the heater. I pressed the latch and pulled with needle-nose pliers, all to no avail.
A thermal fuse rated to trip at 135 °C is hidden near the base of the heater.
This safety measure is necessary because the hot air gun has no temperature regulation, and if the fan stops, things will go badly.


For extra insulation, there's a glass tube inside the metal housing, with another tube made of mica inside it.
I took the hot air gun apart after it had thoroughly warmed up, and I guess that's why I couldn't remove the glass tube. I didn't want to break it. That's exactly why you shouldn't tap on the metal part.


Now let's move on to the tests.
I'll start with a test without nozzles. As you can see, there's quite a large difference between the thermometer reading and the actual temperature.
The photos were taken as it warmed up in max mode.


Here I’ve installed the nozzle with a 5 mm opening. The temperature rise is immediately noticeable because the airflow has slowed down, and there’s no temperature control.


Here’s what the temperature-versus-time graph looks like during warm-up. The recording was set for 2 minutes. At the end, you can see the temperature drop on the second screen—that’s when I gave up and reduced the heater power, since the temperature was still climbing.


For comparison, here’s the same kind of graph for a compressor-type hot air gun with temperature stabilization.
The temperature was set to 350 degrees. In reality, it fluctuated around 350–360, and the thermometer showed a slight positive offset.
But the graph clearly shows the warm-up phase and the transition to temperature stabilization.


While taking it apart, I made a small modification to the hot air gun. I’d seen reports online about the fan’s power regulator overheating, so I drilled several holes in the side of the handle, in front of the regulator.
I also enlarged the holes in the rear cover a little; they seemed awfully small to me. The thing is, at first I thought the fan was at the back and pushed air through the whole assembly. It’s easier for a fan to push air than to pull it. When the fan doesn’t get enough air, it starts to “choke” and can’t generate much pressure, so I enlarged the holes at the back.


A few words about ease of use. Compared with the old hot air gun, this one is certainly bulkier and less convenient. But in practice, there are pros and cons. Yes, it’s bigger, but the old hot air gun has a hose that’s awkward to work with. This one just has a cable, which you could replace with a more flexible one if you wanted, making it even more convenient.
So, in this test, it’s a tie: 1:1.


As a quick demonstration, I made a few videos. As always, the camera is shaky, and the video was shot on a soldering iron camera, so the quality isn’t great.
First, a demonstration without a nozzle: warm-up with the heater and fan at maximum power, then reducing the fan power, followed by switching off the heater and cooling down with maximum airflow.

The sequence is the same as in the previous video, but this time with the 5 mm nozzle.


And here’s the compressor-type hot air gun. The video is stitched together from two clips, but together they show almost the same test as above, with the 5 mm nozzle. The sequence is a little different, though: set the temperature to 350 degrees, raise the airflow to 72% (I rarely use 100%; usually it’s 50–70%), warm up, then stabilize the temperature. After that, I switched off the hot air gun (without turning off the station). The automatic control set the airflow to maximum, switched off the heater, and cooled it down to 90 degrees for safe shutdown—something the hot air gun under review doesn’t do.
You can also see the difference in cooling speed: the compressor-type hot air gun has less thermal inertia, so it heats up and cools down noticeably faster.


Next, I planned to shoot a video demonstrating the difference in how they perform when desoldering electronic components. I even found identical circuit boards for a fair test, but never got around to filming it.
There are two reasons why there’s no video:
1. It’s simply awkward to film, solder, and lift the component at the same time. I only have two hands, but I’d need three.
2. I tried using this hot air gun as a soldering iron, and it’s really inconvenient. The time it takes to remove a component from the board is several times longer.
But besides the inconvenience, there’s another drawback when using this hot air gun to work on circuit boards: it has no temperature stabilization.
Ideally, you should follow a thermal profile when working with components. These are often included in the datasheets for ICs and other electronic components.
What is a thermal profile? When heating a component, you shouldn’t just heat it up; you should do it in stages. For example, very roughly, heat it to 200 degrees for half a minute, then raise the temperature to 350 for a few seconds, and then lower it.
Advanced stations can run thermal profiles automatically. With simpler ones, you do the same thing by hand; with the very basic ones, you can forget about it altogether.

If you’re really interested, I can try to shoot a video, of course, but I don’t think it would be worthwhile.

Now I can finally list the pros and cons of this hot air gun.
Pros
It does work, after all.
Quiet
Relatively comfortable to use.
Convenient stand included
European power plug.

Cons
No temperature stabilization
Low airflow when using narrow nozzles.
The built-in thermometer has a large temperature measurement error.
Power is lower than advertised

Now, a little more detail on the pros and cons.
What’s the difference between a compressor-type hot air gun and a fan-type one? A fan-powered gun can easily deliver high airflow, but it can’t generate much pressure. High airflow is useful for heating large areas, so a compressor-type gun is at a disadvantage here. But a compressor can easily generate high pressure, which makes it convenient to use with small-diameter nozzles. That’s why I didn’t even try the 3 mm nozzle: the 5 mm one was already pushing it to the limit. With narrow nozzles, airflow from a fan-powered gun drops sharply, while airflow from a compressor-type gun increases because the compressor can generate high pressure. That’s what I was interested in comparing. I knew the theory, but had never tried it in practice.
The second issue is temperature stabilization. The temperature of the air stream from the hot air gun under review depends on everything: nozzle diameter, heater power, and fan power. I’d more or less set the temperature, put on a nozzle, and the temperature changed. I’d adjust the fan power, and the temperature changed again :(

As for ergonomics, I expected worse. Strangely enough, it’s comfortable to use. Another plus is that it’s quiet compared with a compressor-type gun.

So, what’s the verdict? It’s not very suitable for soldering circuit boards (except mainly for desoldering), but it should work well for heat-shrink tubing and plastic, where precise temperature control isn’t needed. So it can certainly have its place. The hot air gun is also easy to modify to increase airflow and raise the power to the advertised 450 W.

That’s about it. I still really want to find a hot air gun to replace my compressor-type one, because I’d like to get the station off my desk. Maybe someone can recommend a good alternative.