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- เผยแพร่เมื่อ 26 ก.ย. 2024
- David2's Yihau/WEP 898D+ SMD rework station literally melted down!
Autopsy time.
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For those asking, I checked the TRIAC. It hasn't failed short, but it doesn't detect as a TRIAC with the Mtester (possible not enough current for that). Quick follow-up video coming shortly.
Ok after seeing this, you make me wanna remake my hot air stations control board...... off brand Atten,i think, 858D...
Could be latchup, might not have zero crossed to shut off, could be a cosmic ray hit it at just the wrong moment....
is there a blocking cap across it?
I've had a diferent chinese model at work fail where the comparator in regulation circuit failed and it constantly drove the heating element.
This would have been my guess. Triac/mosfet failure.
Probably taking over the Weller mentality: everything is a fuse if you use it wrong enough.
Every ship can be a minesweeper...
...Once.
“Everything is a fuse if you use it wrong enough!” Needs to on a teeshirt!
This is why every bench needs an "Explosion Containment Pie Dish" for just such an emergency! :)
Big Clive
Ah, true. Just like Clive has one for "lithium and chemical explosions", would be nice to see dave use a few.
Jeffrey [Equine Sanctuary] Unfortunately this would have been way too hot for the explosion containment pie dish, it was melting the metal while receiving fresh power until unplugged.
Yep Big Clive convinced me too! I have the "Pie Explosion Dish" on my bench just for such occasions... :D
@@BrucesWorldofStuff They're very useful for little lithium incidents, like stabbing the lithium cell with your spudger.
The reed switch doesn't control the fan, the temperature feedback loop does. It keeps running for a minute or so after the handle is put on the rest. If the fan stopped as soon as the handle was put down, then it was certainly a fan failure.
You are particularly right. The reed switch is feedback to the controller to know to shut down the heater and fan once cooled.
@@wolvenar I believe when he put it down the reed wasn't triggered and fan happened to die. Now what caused the overheating was without the fan blowing the thermistor wouldn't get a proper reading now. It might have actually detected cooler temps from not having air passed through the length of element and raised temp to compensate.
This was my thinking as well. I don't believe it actuated the reed switch when he put it down, and the fan failed at that exact moment - the fan should have kept on going as long as the heater was over 100C. That should have been his first clue.
I've had my fan start up again if there's any residual heat (I have a Yihua 878).
Dave is right, it should have still tried to regulated the temperature, however with no airflow happening all bets are off.
@@JJayzX Pretty much spot on I would guess as well. Though at some point the thermistor should have gotten warm enough. Probably to warm to be safe though.
Not neccesarily, if the heater is designed to operate safely only at a fraction of the applied voltage, thus relying on a pwm scheme of sorts to keep the average power down, then a triac or controller failure could easily overpower the fan's cooling ability.
Dave, pay David so he can buy a decent rework station! ;)
Aye, Wouter. This. A thousand times, this.
David needs to pay David more 😂
A nice Quick 861D :)
@@EscapeMCP Type it right if you want to spam something. RossmanN. Double N.
Over the years he made more than enough money with that, no he throw out some thousand bucks for a JBC soldering iron plus some thousand bucks for the station and some hundret bucks for some new tips.
Not vibration isolation but seal to force all air forward.
Yep, does that too.
@@EEVblog Pretty sure that's its primary if not only intended function.
Sure, gotta make sure the air flow out and not backwards.
Why not a more hands on look into the problem instead of just speculation? You didn't even show a multimeter in this video. New lab not setup enough yet to hook up to the heating element, re-solder the fan and power it up and check things and actually determine where the failure was? Or just not worth your time?
He should check the wires from hand piece to the station for continuity, especially the wires for the thermocouple.
Dave is not going to do more than that to check a lowly Yehaaa, Yahoo, or any other brand that costs less than $1000!
James Kerns Jr. Consider the effect of such an investigation though, there's more value investigating one of these because far more people have these than have $1000+ stations. As well, the $1000 stations are (usually) good anyway. The cheap ones need more work to figure out which ones are good enough.
@@mckryall Oh I agree with you, I'm just saying you clicked to the wrong channel for that! Dave is the electronics snob of TH-cam. And I'm not making fun of the Yahua either, I have 1 rework/solder station, 2 temp controlled solder pens, 1 DC lab power supply and a "Big Clive" 'lil USB power supply with Big Clive Mod! I also have 2 older Wellers when they were really good, and I wont spend anymore the money for the Weller tips. I'm sorry they are not noticeably better to me, I think I'd rather use the Yihua, so you will not hear me bashing them. It's also not like that thing should be left unattended anyway, even though that doesn't give an excuse for poor electrical safety, which does bother me.
You are right. Dave doesn't make much use of his equipment in these videos. If he restricted himself to power banks and LED lights the voice would be the only difference to Big Clive.
Yeah, I have one of these (similar), and the thermal sensor is in the path of the airflow (where you'd want it to be). You only care what the temperature of the air is during operation, not the coil (until it goes meltdown). Likely, a thermal fuse on the coil would be what you want. I could tell because if I set the airflow to near zero, the coil would just turn on all the time and get quite toasty in a hurry.
I suspect the triac is the original fault, shorted out so the element didn’t power down when it was put back in the cradle, so the controller tried to shut it off and turned off the control signals for the fan and element, but if the triac shorted the element wouldn’t be able to have its power shut off.
That doesn't explain the failed fan though. Bit of a coincidence to get a TRIAC and fan failure at the same time, unless the fan failure caused the TRIAC failure somehow (I don't see the opposite happening)
There’s several videos online where the TRIAC has failed in these models and caused exactly the same outcome; I think the TRIAC (knockoff part?) failed while using it and didn’t go nuclear until it was put back on the holder.. I’d bet the heater wrecked the fan if anything.
EEVblog - I know you measured the fan but maybe it’s internal control fooled your test, have you tried powering it?
@@EEVblog overhead from the failed control killed the fan?
@@TheDefpom but is the triac actually failed?
"sol dering station" is probably because the other side is "smd rework station" - they just separated both words after 3 and after another 6 characters. With smd rework, it fits fine. With soldering, it fits only after the second break, but hey, if you don't know how to read our characters, if you only know how to read Chinese, it would be just as hard as it is for us trying to write something in Chinese and getting it right.
I think I would check with someone who knows Chinese before I print something that goes into production ;)
No, English obviously has spaces in between words to prevent you from those mistakes. Chinese does not. And second of all, yes you`d think they would check at least for a minute before they put that on there. So that's still a retarded mistake and shows their general company working style which probably is the actual reason why that device failed the way it did.
I never actually measured it, but wouldn't a brushless DC fan always measure open circuit since there's a bunch of transistors between the supply an the stator?
Precisely. A simple test by applying 24V DC to it would have been a definitive test. I have a similar station where the fan driver circuit failed, the fan itself is good and the hot air gun tests fine on an identical unit. I watched this video hoping to find out which component might be the culprit on mine but it was just a waste of time. The commentary really pissed me off, his high pitched squeaky non-stop voice is very irritating and he displays a contemptuous dismissive regard for what he is looking at and doesn't understand.
Wow thats a lot of butt hurt for one soy boi.
Firstly, give there were ONLY 2 wires to the motor... its not going to have transistors in it. Secondly, the price and cheapest option ethos kind of suggest a straight forward dc fan...
And thirdly.. this guy is an expert who would have seen the truth in a reading of ohms that would have suggested another type.
Your comments make you look a fool with little or no real depth of knowlege, and absolutely no respect.
You are a muppet. And youre full of shit. Too full. Its comming out your mouth.
And even this thing has a fuse WELLER!
i laugh but tbh this isn't even funny, my father and a good old professor on EE told me to get a weller as i am setting up my bench, then thankfully seen Dave's vid and got a hakko, they really made a name for themselves in the past that they do their best to ruin it now
Weller is a big fuse itself...
Weller has its fingers in its ears and yelling lalalalalalala
Oversized fused so it's no better then the weller..
@@kapioskapiopoylos7338 The Hakko FX-888D is a great soldering iron for setting up an electronics workbench. I'd go for that over the Weller!
While a 6A fuse may have been over-rated for the application, a more appropriate 4A fuse still wouldn't have changed anything about the hot-air wand melting down from fan failure as the element was likely operating normally at the time. The fuse only does any good when something fails in a way that causes excess current draw long enough to blow it.
A bit puzzled about why the temperature regulation didn't reduce the heater's duty cycle after the fan stopped. Did the TRIAC or thermocouple short out? I know my similar-looking cheapo hot-air station is pretty quick at throttling heater power when I change airflow.
My school outfitted their lab with 853D's (which feature the same heatgun, etc. + power "supply")
I've seen a few of them meltdown in a similar manner.
There's a software bug (in the 853Ds we had) : if you keep cycling it between active/holstered in a short amount of time the processor locks up and stays in a random-state {(fast) heating up, steady w/ fan, cooling off, off}.
The workaround was to listen for the fan to shut off on holstering. If immediate then switch the unit off then on again, and don't leave anything heat-sensitive where the holstered heat gun is pointing. (Was actually convenient when shrink wrapping stuff.)
OFC with sixty hot airguns to choose from, this wasn't a serious issue, unlike the input filters starting smoldering fires because of an inappropriate component choice(?) Those all got replaced/retrofitted before being installed so I can only guess what the TI changed.
That would be a good info to put into the 898/853 thread on the eevblog forum. A lot of the people have studied all the variants and started doing mods to make them safer.
Maybe a MCU brown out without a proper watchdog routine.
I think David nearly had a brown-out when the thing started to meltdown in his hand!
@@Zadster Accurate
Wouldn't suprise me one bit. Hastily compiled chinesium grade lazy slack-ware is in everything. 32K bloatware just for the SPI interface driver..... 5,458 clock cycles to execute 1 instruction. Embedded windows on an ARM chip to blink 1 LED... Use an external A/D converter because the slackware compiler tool couldnt use the internal A/D....
"Input fused. There you go Weller."
Shots fired.
So as I am considering one of these as a hobby station for occasional use, the build quality of this seems sufficiently good. A fan burning out after 3 or 4 years of substantial use doesn't seem to be a show stopper, especially if one turns the unit off at the switch rather than flapping the red hot thingy around in mid air while wondering wtf to do, haha.
These companies are tested daily by corner repair shops in China. They have to have some quality to survive the market.
If the thermocouple is the only sensor in the handle, then without airflow, you obviously can't detect the runaway fast enough, as you will be relying upon convection only. So the plastic (in the base) will melt long before convection gets the thermocouple (at the exit) up to the set point of, say 400 degress C. Other strategy(ies) will be required.
It's covered in metal and mica insulation so I don't think radiant heat would be too bad.
Richard Rudek I think it'd get VERY hot sitting next to all of those heaters, hot enough to trigger a cutoff if the cutoff circuitry were functional
Nup. This guys on the money. You ever put your hand over the back of a hair dryer? No heat out the end and glowing element wires in about 3 seconds
it would be interesting to test the actual output of the sensor whith the fan off.
not sure how duable in the states this station currently is
well third wire (speed feedback) on fan would prevent overheating due to insufficient air flow (stuck fan) but wouldn't if blades were broken and motor idly rotating.
*_Yeehaw 898D_*
Ive got the same gun. I always stare at the temp to make sure its cooling down when it put it in the holder.
I sure hope that the white insulation material isn’t asbestos!
I'm curious what that material that is. I took out a thermal fuse out of my hot air gun and that stuff feels like some sort glass fiber
Ed Gein It is! If you google mica heater you get tons of results at alibaba
It's mica. A naturally occuring mineral just like asbestos, but the flakes are quite different in shape compared to asbestos and aren't known as carcinogenic. Since it's so flaky, it isn't usually used as a wrapper. It may have been reinforced.
Looks like mica + glass fiber to me
According to my book it’s a mica wrap. I have a spare heating element. It says do not remove mica wrap to avoid short circuits.
19:23 this fan is bldc, it have own driver on board. You can't verify it like that!
bldc wouldn't register as open
I have a few of those fans ... They do not show impedance.
I was yelling that at the screen when Dave came back and said it measured open. Surely he could plug it into a bench supply and verify.
Wait, can anything show as an open circuit and still do something when fed 5 V?
@M Rios Say that red wire goes to the gate of a controlling mosfet, or some sort of cmos input.
Could it be possible there is a malfunction with the Triac? Don't know much about them, but wow, surprising it failed like that. Terrible!
That would be my guess also. Testing the fan should also have been done by applying power to it instead of measuring it's resistance. I don't think that's a valid test if it's brushless for example, or if there's a diode in series with power input
There are several possibilities like that. They are usually pretty robust though.
I put my bet onto it too.
That doesn't explain the failed fan though. Bit of a coincidence to get a TRIAC and fan failure at the same time, unless the fan failure caused the TRIAC failure somehow (I don't see the opposite happening)
My first guess was that the heater control triac went shorted, but if the fan had indeed failed then perhaps it's something else.
If the fan died first, then my theory is that once it failed, there was no airflow to keep the thermocouple 'updated' with the real heater temperature for some time, thus the software did not notice any significant change and did not reduce the duty cycle. Because of this, the heater temperature increased very quickly. By the time the thermocouple tracked the actual temperature of the heater by convection, the temperature value may have been so high (in software) that it was 'out of bounds' to what the program expected, and thus it (the program) did not know what to do or ignored it completely. I wouldn't be surprised if a badly written program with no sanity checking or edge-case testing caused the runaway condition following some hardware failure, but at the same time, I agree with Jimmy Pedersen, a simple resistance check on the fan isn't that conclusive, so maybe it really is just a shorted triac.
Well and truly wellered.
Well said
18:50.. Since so many of us have one of these WEP rework stations... why not get a functioning one and put it through some possible error conditions to see where it will/may fail ???
Then find a solution to the fail so what happened to David won't burn down our homes.
Just quickly looking at it I can see adding a parallel reed switch to the opposite side of the hand held unit and perhaps a Thermal cutoff switch right at the element supply.
BTW.. my 858D has been working flawlessly for the past 4 years.
Thanks for an interesting post mortem!
Just a tiny note from an ex cable manufacturer: Quite unlikely that you would find 8 strand wires. The geometries favor 1 center & 6 around, which equals 7. The next one, used for more flexible wires would be 19 strands, (1+6+12).
Never leave the area when this tool cools down, keep an eye and an ear on it, a nice trick is to slightly increase the fan speed, and it should cool down more rapidly. Great tool for the price. I also often rotate the tool until i see temperature decreases...
Bucket of Sand.
It's old school but a bucket of sand is great for electronics fires like Dave had and it's not as much of a commitment as breaking out the fire extinguisher.
Heat regulation keeps the output at a set temperature, if the fan fails the output temp stays the same but there is no cooling air to protect the plastic from melting. The heat which is normally carried away finds it way back to the plastic housing. Seems like a second temp sensor would be a good safety feature.
Harman Robotics Even some type of sanity check of the output duty vs sensed temperature- if output is too low, poor airflow is suspected, alarm and turn off output...
Or a thermal switch in the resistor for overheat protection
OR JUST PUT THE DAMN SENSOR NEXT TO THE HOT COIL INSTEAD HAVING IT 25 MILES AWAY. (Black insulation can keep your isolation.)
My Atten 858D+ v3.0 also does the same thing if I have it in my hand (fan and heating element are working) and then press the middle "store/call" button. The fan stops working and the temperature shoots through the roof, smoke included. Took me couple of seconds to realize what's going on so I quickly changed the temperature which caused the fan to start again. Firmware bug.
I have a 853D 3 "N" 1 and it has done the same thing twice and I figured it out fast and turned down the temp. Also if I have the little end on it [3mm I think] and the fan is turned down all the way it overheats for a few seconds and the temp sensor backs it down. So now if I am going to turn down the fan I also turn down the temp and it evens out as the set point when first started...
I had almost exactly the same thing happen a few months ago. Same WEP brand. It was an air-only model. I set it on the cradle, and a few seconds later I heard a POP and my lights flickered. I looked over, and the whole metal part of the blower was orange hot. I am absolutely sure that the fan was still running. I hit the power switch immediately and unplugged the unit from the wall.
There was no smoke or flame. I took the handle apart and there wasn't any noticeable damage to anything. There was a small spot up on the metal casing that *looked* like the heating element had shorted and created a weld. I took the chance and tried turning it on again in a safe location. The fan ran but the heater did not come on.
"Fortunately" mine was only a couple weeks old and I was able to return it to Amazon for a refund.
Looking in forums afterwards, I read some of the best advice for these: It's good for the price but only use it in the middle of your driveway with a fire extinguisher handy.
I also have a 898D from another company, and one of the greatest dangers of those devices, is that they will start when removed from the holder, EVEN IF YOU SHUT THEM DOWN FROM THE CONTROL PANEL. And by the way, mine had no information sheet whatsoever to tell ma about this magnetic switch behaviour - which made me thing first that it had spurious restarts until I realised it was when I removed it from the holder...
7:10 because red color means where electrons are flowing from.... duh everyone knows that electrons are blue
Weller : Fuses are overrated. Meh.
WEP : Meh. Over-rate the fuse.
Oh my god..... now i understand trump..
The thermal couple was properly located beyond the last coil of the output. But when the fan cut off and the tool was docked, it was at the bottom of the heat coil. As heat rises, the cool air is drawn into the nozzle passing over the thermal couple telling the processor to increase heat. Even if the thermal coupling was working fine, the heater housing would be kept far hotter than designed.
NOTE the standard was changed from 240-V to 230-V some 20 years ago,
and in Europe, it was changed from 220-V to 230-V
Though as you know voltage will fluctuate slightly.
And just like a slot-machine the voltage variation can be a current operated
money machine for the utility companies.
I've got one of the similar model (YiHUA 8786D I believe) for my first year in college. Back then it only cost me ¥200(~$30) or so for both a rework and a soldering station, which was quite an affordable price for amateur student hobbiests like me. The station works pretty fine for a year, before I decided to go 'professional' and bought a ¥150(~$22) standalone T12 soldering station. But the rework function of that YiHUA model is still used until now, which helps me get through a great amount of troubles in the past year without any failure, and that magnet is actually very sensitive and reliable.
One thing I've noticed is the temperature sensor on the airgun is not directly mounted to the heating element, which is quite reasonable because it is supposed to measure the heat of the airflow, not the heater. That means it requires the heat to transfer through the air gap before the sensor can sense it, and with the absence of airflow the heater can heat up dramatically before the sensor reach the target temperature. Another thing is that the airgun still blow air to cool down after it is placed back onto the holder, which means it is very easy to spot a fan failure at the scene, and you probably don't want to leave things like this working away from the scene.
Anyway, you get what you pay for, don't expect too high on a cheap model, otherwise the producer won't get enough profit to survive.😉
This is why I personally do never ever recommend cheap tools to beginners. When you do a review and show them that these things work and are usable, these end up in children bedrooms, hobby labs and all other kind of environments where an epic fail like this one cannot be contained properly - especially when the device is handled by an inexperienced person that has never experienced something going south that quickly. Those people might burn down their houses.
Devices of such questionable origin should not be recommended to anybody. They are dangerous.
I would have expected something like this to have two independent temperature sensors / cutoffs.
The temp sensor would be expecting such high temps as its in the airflow section on the blower, its used for temp select not as a safety device, it was probably regulating the temp as spec but without the airflow the heat just built up in the handle.
GooleyGaz Yeah I think I can agree on that. The plastics are not going to take even 300C so the regulation could be just fine and it would still fuck up everything
A thermal fuse inside the housing would have saved it from melting, along with a software change and you're good to go. All David needs is a new hot air gun, a thermal fuse and you'll have it up and running in no time. I think they designed it to be pointing down when in the cradle which isn't very ergonomic, next one, cover the cradle in magnets.
the fan does not stop when its on the cradle until it reaches 100 degrees so he should have known something was wrong as soon as the fan stopped and the degrees had not counted down
I had the same unit for ages, the fan on mine stopped working within a few years. I simply replaced it with a better quality fan. I since upgraded and gave the unit to a family friend. Who to the best of my knowledge still uses it.
when the fan on yours stopped working, did the plastic melt down like the one in the video? what replacement fan did you use?
The fan measuring open just indicates the electronics in the fan are not shorted. The only valid test is to power the fan up and see if it runs. It's a brush-less DC motor.
It's obvious based on David's description. He said the fan cut off, but not the heater. The fan is not supposed to stop when placed in the holder. It only stops when the temperature drops below a level, like 100 degrees. This means the fan failed, or a fault in the circuit providing power to the fan. The reason it overheated is because the reed switch was not activated so the heater remained on. The temperature sensor position measures the hot air blowing over it. Without the air blowing, there would be a huge temperature difference between the heater and the sensor.
More like a "Smol-dering Station", am I right?!?
He did get years out of it for a cheap unit. Can't complain too much about that for the price if it lasted for years.
Good to just be aware they could fail in a bad way.
You could add an additional thermal fuse to try and prevent meltdown in case of firmware bugs.
Gas central heating boilers in the UK have an air flow switch, which detects when the fan is blowing air into the combustion chamber (or drawing out the exhaust, on older ones -- these were inherently safe against leaking carbon monoxide as the firebox was under negative pressure wrt the room). The air pressure switch must be in the NC position for the fan to start, then a relay latches it on; and the switch must have moved over to the NO position, with the relay latched, for any power to get to the gas valve and the ignition spark generator. Then the gas valve will remain closed if it the flame detector thinks it is seeing a flame when the fan switch first changes over, so it must see a no-flame condition before sending any gas to the burner and starting to spark. There are also two timers: one which allows the combustion chamber to be purged with fresh air before the gas valve opens and the spark generator is energised, and a second which cuts off the gas valve and spark if no flame is detected within a certain time limit.
A fan proving circuit similar to that in a gas boiler would have required just one low-operating-force microswitch to detect air flow and one relay, and would have prevented this situation by cutting off the heater if the air was not flowing. (As you say, misplacing the unit on its rest so the off-switch did not activate and then the fan stopping with the heater still active would be hard to notice, especially if the vibration from putting the tool on the rest was what finally finished off the fan. Dry solder joint on coil, broken wire ..... plenty of likely suspects there.)
Of course another -- probably even simpler -- solution would have been to fit a one-time thermal fuse in series with the heater, ordinarily cooled by the air flowing past it but heating up quickly if the air stopped.
bluerizlagirl The air flow sensor you speak of is literally a themistor connected directly to microcontroller pins, with a capacitor across. The MCU heats up the thermistor and uses the RC time constant to measure temperature change. One can use a second resistor and the built-in ADC on that pin, instead of the capacitor, but the RC scheme works with the cheapest of the micros. That of course assumes decent firmware and a properly configured watchdog, and circuit design that fails safe when the MCU dies.
SCR went short hence the thermal control was lost. Also the fan has control electronics and cannot be measured as a coil..
It seems the triac or whatever is driving the triac failed. That's why the reed switch responded and turned off the fan and the temperature feedback sensor couldn't turn off the element. They should include a physical thermal cutoff switch near the element to prevent this.
Shouldn't there also be a last-resort one-off thermal fuse to kill power to the element if the handpiece goes above its operating range?
I think they include them on electric kettles and things like that, with something like two springs joined by a blob of temperature-specific alloy.
If you buy one of these make sure you inspect it internally before using it they're hit & miss assembly wise
one problem I noticed is that the temp probe requires airflow for proper sensing. it wouldn't explain this fail because it would have sense the temp before it went completely nuclear but it could be a contributor.
Four hours for this cheap tool is just amazing and you had it for years. This is amazing!
Got the same trouble on similar device. I turned air flow button to minimum (actually no air flow at all) but temp was set quite high (360°C). Just holding it by hand while talking to somebody, the thing went very bright red and the plastic handle melted. The fact is the heater start heating on the handle side, the end side was probably hot but not reddish and below 360°C, so I guess the sensor at the end of ceramic element without air flow is just useless in this case. Now I know it, and pay attention to always set air to max before hanging on.
I was using my WEP 858D today and had a similar problem... Fan was on full, working at 385 degrees and the next thing I know the barrel where the heating element is was red hot! I looked at the temperature readout and it read over 700 degrees and it's max temp is 500! (all temps in Celsius) I quickly shut it down before it had a complete melt down like in this video. Needless to say a new hot air station is on order, not one of these though... Still going cheap but not super cheap.
i have yihua 992DA+ from the manufacture shop for more than a year and I must say that I am very pleased with it, very reliable and good quality
Unfortunately, as we have seen recently, buying a premium brand is no guarantee of safety or reliability. They all seem to rely on one component in the protection system. If that fails then you are stuffed.
Purchased a year ago. I found it did not always seat properly in cradle to shut down and no cable disconnect for the hot air rework like for the soldering iron. Definitely should never be left unattended, unless completely unplugged!
You two gave me really good laugh, I wish there will be more videos of this kind :)
David actually said that the fan was the problem way before Dave.
I see that the Mains fuse is wired incorrectly. The live wire should go to the tip end of the fuse holder, not the side contact. The way that it is wired, it would be possible to get an electric shock (through the fuse itself) during replacement of the fuse with the power on.
The shiny insulation is probably Mica. The thermistor probably wont measure the temperature correctly if there is no airflow. A simple flow sensor or a fan with speed sense would solve this problem.
If the fan fails, it won't push the heated air over that thermistor at the front of the heating element. So the sensor is not representative of the actual temperature.
I enjoyed the tear-down. Thanks for the entertainment. I wouldn't trust that micro in a socket unless it was a machined-pin socket. A few years and a bit of oxide and the thermocouple might not get read, or the heater shutoff reed switch might not get read. But I just bought one that looks very much like this one so I believe I'll pop the lids and do a bit of PM on it and put a mark on the shell of the wand where the reed SW is. My bench is going to look pretty silly with one of these sitting next to my trusty old Metcal iron, but I retired before I got very far into SMT work, so any new SMT soldering gear is consumer grade. But thank you for pointing out where I should do a bit of upgrading on it.
The 120V version has the same 6A fuse. It's probably something they didn't bother to change between 120/240V models.
I had the same one for 8 years or so. A month ago, I picked up the soldering iron, and I could see it was glowing a dull red and I could feel the heat radiating a foot away. Dumpstered it and got the pace one you reviewed. It was quite an upgrade.
Those things are a bit of an adventure. Not for hard use. I bought one, not sure specific name, of just the hot air. Tested reasonable on the fusing and ground, but not upon closer examination. For one thing the neutral was switched, so I swapped that around and ran better ground wires.
But they work by fan cooling down to about 100 C. If the fan failed, even if the element shut off, that heat that is usually blown out was trapped and could only go into the plastic. Incident sounded like smoldering plastic, which you can get from just heat dissipation.
Essential mod for these units is install a main power switch. Mine had a hole already cut out for one on the back panel, it was just taped off so a quick install with a 50¢ rocker. Another common failure is the Darlington transistor. I relocated mine off the main board so I could fit it with a larger heatsink. After replacing that though it's been going strong for 5+ years and use it several times a week. Not a pro unit but good enough for the hobbyist like myself. But install that switch or at the very least unplug it when not in use.
The magnet should be (centred) in the hand held heater unit and the reed switch in the holder instead, a mercury switch (or similar) so that if no movement is detected the heater will power down or go into low heat mode, a tac sensor on the blower motor and said thermocouple in conjunction with a heat fuse.. would be almost fool proof for $5 -10 dollars on the BOM
That thermal sensor looks too far away from the actual heater for me. Maybe it wasn't registering anything faulty due to the low thermal conductivity of the ceramic base while the thing was already melting, and the missing airflow was supposed to be moving the heat from the coils onto the sensor, but obviously wasn't there to do that?
On my YiHUA 898 D+, when cradled the blower stays on until the temperature is below 100 and orientation doesn't matter. Features that Davids did not seem to have.
I wonder why there is no thermal fuse to be found, though.
Probably cost reduction
@@iuri.castro They could have done with fewer connectors on that PCB to reduce cost
@Iuri Castro but those things cost 50 cents tops, even cheaper in volume. I don't see how having a thermal fuse could impact revenue significantly...
Well, the entire handle is the fuse. When it melts down you buy a new one. It's dirt cheap in China.
Just put a solder blob over small components to remove them with a soldering iron.
Far less reheating of the board and surrounding components!
Faults pretty clear to me. The thermocouple is a good 10mm away from the element wire. When the fan blew, there was nothing but convection and conduction to move hot air past thermocouple; it was no longer being forced past. This would make it take a reasonably long time for the thermocouple to register the true temperature of the element, certainly longer than it took for heat to conduct through that thin insulation and the metal can. Looks like they needed a separate thermal cut out in closer proximity to the element to catch an overheating scenario with no airflow
This sounds most likely to me.
It would have stopped heating the element as soon as it got to the temperature. The sensor is not that far away so the effect would have been a slow melt-down instead of a burn-down. At least that's what I can figure from the witness' recollection. I'm betting on a software error as hinted by some other commenter above.
On point, there is still heat but ghe difference to set temperature is huge, definitly high enough go keep on heating, the most perfect solution would be a thermocouple within the heating element and an airflow sensor, but a second TC would be enough, if there is a max temp set for it in the firmware.
Looks like the microcontroler failed to detect the open circuit fan, I agree with this synopsis.
even if it has an overheating protection in software i think the termocouple was not able to detect temperature because of its position. It seems to be placed inside the ceramic insulation and in contact only with the hot air, so no air no temperature
4 hours reflow job and 3 years of use, I am not disappointed. I have a Burntop version.
since you can set the airflow and the temp separately .... its Obvious the heater was not straight on the mains !
Could it be that the fan motor itself went bad?
I'm surprised this has happened, since I have an identical unit which I've been using for over 10 years, yet haven't had a problem with it. The reed switch is a bit finicky, so care must be taken when putting the heating head back on the cradle.
Why wouldn't you suggest buying it? It lasted for years for 60.00 and it probably paid for itself 100 times over. You should repair the thing, wrap the nichrome in fiberglass skirt, up grade the ground wire, test the thermal-couple and it would probably last for many years to come.
It may be that the element continued to be regulated at an elevated temperature when the fan failed, the temp. sense is down stream of the air so when the air flow stops it only gets radiated heat which would make the device think the element is cooler than it is.
Check the triac! They are known for triac failures. Usually these units turn off the heater, leave the fan on until they reach about ~100°C. - Then the fan will turn off.
Maybe, but doesn't explain fan failure at the same time.
You paid $40 for it and used it in a commercial environment for years and expect it to last you a lifetime? I'd like to see what you can build and sell for $40.
the case maybe, unpainted...
It was David's personal station. Not a commercial environment as far as I know. I don't think they expected it to last a lifetime, but to fail safe and not fail catastrophic
@@JockMurphy well the sad thing is the sensor and the micro was there so without further costs it could have prevented the catastrophy
He didn't expect that, but the failure mode sure is worth mentioning.
@@kapioskapiopoylos7338 The micro could have checked that the temperature went down after the reed switch was engaged. It could have cut off after X minutes and required restarting just in case, etc. There were options
My 853D unit hot gun burnt the element. During the first use, and after several tests, it went haywire. The heating element got so hot that the color of SS pipe went blue. I could actually see orange color from the nozzle. it was sitting on the cradle too. The sell is unresponsive so far, so I found a replacement element. the challenge is the re attaching the ground wire to the SS metal pipe. I plan to use conductive epoxy. Wish me luck.
I wonder if more magnets at the holder will insure no matter how the handle is sitting the reed switch is controlled.
The reed switch should turn off the element not the fan for me.
The fan should stay running for a set period using a simple timing circuit and maybe a thermisistor added in the handle for extra safety.
Got the "genuine" Yihua one for couple years now. Still works. But at max temp. hot air barely de solder any component. Even on low thermal mass boards. I guess you get what you pay for. Need to upgrade to proper hot air, like Quick 861DW now that is a HOT AIR station.
And not a thermal fuse 1 to be found ...Bueller Bueller ........Bueller
@@invendelirium If the handle gets hotter then 180 inside, something is pretty wrong.
You spelled Weller wrong. :)
This aint one of Dave's best videos. 24 minutes of rambling and not even an attempt at finding out what the problem was. First things to do should have been disconnecting the heater and powering the thing on and try it out. Then measure the triac and try to power up the fan from inside the controller to rule out broken cable or connector. Heat the thermocouple with another hot air station and see if it regulates or not...
Dave "not gonna bother" Jones has become lazy although he still makes the occasional excellent video.
I replaced a total of 3 of these fans inside these cheap reflow stations where the fan was the culprit.... Funny thing is the OEM fans say 24v on the sticker but when you install a real aftermarket 24v fan it runs slower than the original. So... i wised up and bought 10 of the 12v ones, which work beautifully. Ebay has em. I guess they labeled the OEM fans incorrectly.
Every soldered (not crimped) wire will brake exactly on the line of solder tin from a even a little vibration. It is just a question of time here.
I had a soldering station with the same model number 898d+ from a different Chinese manufacturer. It used to crash a lot. Especially on hot air, but usually the opposite was happening. You’d be heating smd and wonder why nothing is melting, then turn your look at the display and it’s blinking with nonsense, and the heat gun is not heating at all!
The difference here is that with this thing you kinda expect it, but with Weller you expect it to be a safe product.
Great teardown! I'm looking to get a rework station and stumbled here. This rework station looks to be a fake - the 7 segment displays look recessed, as compared to the genuine. There's no Yihua logo on the top left panel. The fonts indicating the model number looks different from the genuine too! Thanks for doing this teardown - I'll be more cautious with a purchase now.
Yeah definitely not a real yihua unit, I am getting a hot air station and will get a real yihua, at least I know what I'm getting, this one is crappy.
''Oh yea input fused there you go Weller''
I think the element wire and fibreglass tape needs redoing too. Brittle quality from factory.
Another vote for the triac failure. David was using it for hours, it shorted. When he put it in the cradle, the fan stopped, controller tried to turn the heater off, no can do, meltdown ensued.
How to take someone seriously who admits to working on cardboard and carpet...
With xp you know when it's okay to do certain thing weirdly
Maybe the algorithm was written to control minimum and target temperature but overheat due to lack of fan was a “should never happen” branch in the code?
I use a WEP 952D+ as my main hot air station. The compressor ones have a protection. If it runs the heater but no response from thermocouple it throws an error and shuts off, also if it loses the thermocouple it throws an error and shuts off.
The station I have right now is similar to this one, but when the handle is but back into the holder it instead turns the airflow to the max (in addition to turning the heating off), so I guess they have at least attempted to give it a better chance of survival...