858D hot air station is DANGEROUS!

[exit_failure]

 Some time ago I bought an 858D hot air station. Mine is the version with the detachable hot air gun. I had to open the case for another reason. The first thing I noticed, apart from the case being practically empty, is that while there is a crimped earth connection for the metal case everything except for the ring crimp itself is painted.: The screw that attaches the crimp to the case and the case itself. Using painted metal parts in your grounding is a gigantic NoNo but there are always those who claim that the paint will scape off when putting in screws and that its no big deal anyway.
I measured between the earth connection und the four screws for the feet, which are bare metal and can be touched from the outside. The lowest screw to ground resistance was 5 Ohms. The highest was about 4 Megaohms. I also scraped off some of the paint of the cassis and measured about 700 Milliohms of resistance. The station has a CE mark on it. CE, in this case, would require a maximum resistance to ground of 300 Milliohms to every exposed metal part that the user can touch since there is no double isolation. So right of the bat, the sticker on the back is a blatant lie.


The next thing that I found out is that one of the pins of the connector for the hot air gun is live as soon as you flip the toggle switch and the another will become live if a MOSFET is switched on at the wrong time. By the way: The gate oxide layer of the MOSFET is the only thing between the line voltage and the low voltage side…
Update: pqass pointed out that the gate is isolated by an optocoupler so that is not a concern at least.


At least the metal parts of the hot air gun are properly earthed. So, there’s that…Oh, and as a cherry on top of that potentially deadly cake, the metal casing of the connector is floating. That means that if will become live if you ever are a bit clumsy and bend the wrong Pin when inserting the plug of the hot air station slightly crooked.


Some of the risks can be mitigated by scraping off some paint around the earthing screw and also grounding the connector housing but that still means that there are live connections exposed if the device is switched on an the hot air gun is not attached
Oh well, I guess that means that I’m looking for a new hot air station now. Any recommendations?

[pqass]

The gate oxide layer of the MOSFET is the only thing between the line voltage and the low voltage side…

BTA12 pinout is A1, A2, gate.  The closest "low voltage" side should be on the right side of the white 6 pin opto triac.

Shitty grounding is not surprising. It's almost expected when we [willingly] buy cheap equipment.  Scrape it off, re-measure, and carry on. 

WRT the connector, most designers would use a female on the source-side. But the original designer got that wrong, now every other station maker that wants to reuse the same wand is forced to repeat the same mistake.  This is a hazard for the unwary.  You know better so keep the wand on.

As for a new station, why?  If it meets your needs and you can remedy the issues.  Keep it.

[Gyro]

Yes, I remember this coming up before (more than once). Sadly the manufacturers / sellers of these things in China just don't care. Iirc, the mains fuse holders have a nasty habit of breaking and falling apart too!


Edit: Actually, I don't see a rear panel fuseholder on that one, maybe it was a different model / clone.

[exit_failure]

The gate oxide layer of the MOSFET is the only thing between the line voltage and the low voltage side…

BTA12 pinout is A1, A2, gate.  The closest "low voltage" side should be on the right side of the white 6 pin opto triac.

Ah, you're right. I overlooked the Optocpuler.

Shitty grounding is not surprising. It's almost expected when we

[willingly] buy cheap equipment.  Scrape it off, re-measure, and carry on. 
WRT the connector, most designers would use a female on the source-side. But the original designer got that wrong, now every other station maker that wants to reuse the same wand is forced to repeat the same mistake.  This is a hazard for the unwary.  You know better so keep the wand on.

I know that now but I wonder how many people have that station at home and have no clue about how potentially dangerous those things are.

As for a new station, why?  If it meets your needs and you can remedy the issues.  Keep it.

I sometimes have less experienced and unsupervised people working with my equipment. I just don't want stuff like that standing around or even being used by them.

[exit_failure]

Yes, I remember this coming up before (more than once). Sadly the manufacturers / sellers of these things in China just don't care. Iirc, the mains fuse holders have a nasty habit of breaking and falling apart too!


Edit: Actually, I don't see a rear panel fuseholder on that one, maybe it was a different model / clone.

I actually bought this from a EU seller. I'm out of the warranty period but I think I'll write them an email anyway.There is a fuse holder on the back. It is integrated into the housing of the mains plug socket.

[pqass]

I sometimes have less experienced and unsupervised people working with my equipment. I just don't want stuff like that standing around or even being used by them.

Loctite (or superglue) will keep the curious fingers away.

[Gyro]

Yes, I remember this coming up before (more than once). Sadly the manufacturers / sellers of these things in China just don't care. Iirc, the mains fuse holders have a nasty habit of breaking and falling apart too!


Edit: Actually, I don't see a rear panel fuseholder on that one, maybe it was a different model / clone.

I actually bought this from a EU seller. I'm out of the warranty period but I think I'll write them an email anyway.There is a fuse holder on the back. It is integrated into the housing of the mains plug socket.

If you bought it in the EU, you probably have some legal comeback (depending on whether it is a retailer, random ebay seller etc). You could probably get whatever your equivalent of Trading Standards involved.

[Haenk]

Report.

https://webgate.ec.europa.eu/icsms/public/authoritySearch.jsp?locale=de

Richtlinie 2001/95/EC

[exit_failure]

If you bought it in the EU, you probably have some legal comeback (depending on whether it is a retailer, random ebay seller etc). You could probably get whatever your equivalent of Trading Standards involved.

I did. They wrote me back and told me that they would refund my purchase. They even took the station out of their web shop already. So full marks for them.

[exit_failure]

Until I get a new one I did the following to make the old one safe-ish:

• sanded off the paint of the chassis where the grounding crimp is screwed to the case
• sanded the contact areas of both parts of the metal chassis since they were completely painted an the second part wasn't earthed at all.
• turning the screws of the feet until they made good contact
• earthed the case of the hot air gun socket by putting a loop of wire around it, securing the loop with solder, soldering the other end to the earth connection of the PCB and squeezing the loop between the inner rim of the socket and the plastic front of the case.
• checking all exposed metal parts as to whether the resistance earth is less than 300 Milliohms

[helio0centra@gmail.com]

My first hot air station was a cheapy chinesium one it was called an 8858, which has gotta be related. But it got stuck on the heat and it overheated and caught fire so i threw the whole thing out and got a more normal heat gun from the hardware store.

[MathWizard]

I had mine apart and checked that the fuse was on the hot side, and it was there. But I never thought about the chassis grounding, for circuit breaker protection. I'm pretty sure all the metal was painted white.

Next year I'll probably get a proper HA station.

[BrianG61UK]

The next thing that I found out is that one of the pins of the connector for the hot air gun is live as soon as you flip the toggle switch and the another will become live if a MOSFET is switched on at the wrong time.

For the cheap 858D copys buy one without the connector if you can. I suggest looking for one that just has the cable entering though a strain relief grommet.
In your photo the three terminal semiconductor is marked BTA12 which is the part number of a 600V 12A TRIAC. Which makes much more sense than a MOSFET.

[coppercone2]

Just theoretically speaking, the star washer is designed to be a paint breaker, or an aluminum oxide breaker, for grounds. If they put a star washer, that is unfortunatly acceptable to some people, to use it on a painted surface, but IMO its dodgy. Its designed to work with crappy prep jobs, otherwise a bolt with grease is better, so long its clean, because it will have a slightly lower resistance (vibration aside, it seems natural to assume it increases vibration resistance, but I am not really sure, so you would need to determine that).

Also, something to keep in mind : some people think that those star washers are single use, that they are dulled/deformed after a single use.