EEVblog #1160 - Weller Responds

[thmjpr]

Especially with all the effort/cost that went into protecting the secondary,  leaving the primary without one is totally bewildering.

That is where it gets weird, and a response from a weller engineer would be enlightening.
The mains rated fuse is already there, just on the wrong side of the transformer (the secondary). As established in the last thread, it was designed that way, not an assembly mistake.

[coppercone2]

its not on the 'wrong side'. You put them on both sides if you want, its better. Plenty of documentation on there. But you always want it on the front side.

[santiall]

I'd not be surprised if the station actually passes the safety standards without a problem. I've seen more dangerous products passing the tests and others properly designed failing for whatever minor margin or simply because the safety test operator doesn't understand the standard.

It is not that the standards are also that 'perfect'. I'd need to go through the document but a mains fuse isn't actually compulsory as long as there are other safety means and the product 'fails safe' (maybe a bit of smoke is considered a safe failure as long as there is no fire ). Also, for example, till not long ago you could use a crappy power switch if it was located on the back of the device but a heavy duty one would be deemed unsafe if located on the front. The famous TV-rating nonsense that related back to the 50s probably.

The joy of the safety and EMC approvals 

[blacksheeplogic]

Weller responds to the magic smoke escaping from their WE1010 soldering station, and the lack of a primary side mains fuse.
Prepare to be awestruck at their commitment to safety!

This first video was good, made a mistake, here's what happened, could be better designed. This video adds no value outside of bashing Weller for your mistake... I have both 110 and 230/240 gear, and don't have a problem remembering which is which. If I did, I wouldn't be trying to pass the blame off to the manufacture.

[Xenon]

Mains fuses are not always doing their job.
In my office I had a Weller WTCP51 with a 315mA mains fuse. It was 10 years old when the silicon iron cable shorted internally because the insulation had crumbled for some reason.
The transformer released the magic smoke in under a minute and the mains fuse did not blow.

[johnlsenchak]

I would have  taken  Weller up  on  a free offer  of a   soldering station  just to trash  it further  in a  bad review 

[Towger]

I have to ask the question:  Aside from improper use (which is certainly the case for Dave's experience) has there been any confirmed problems with the lack of a mains fuse reported from units in the wild?

Yes. There is another thread months ago on the forum, which did not get much attention at the time. 

Added link: https://www.eevblog.com/forum/repair/repairing-a-weller-soldering-station/

[EEVblog]

The first video well oops I screwed up but if it had a fuse maybe it wouldn't have. That is debatable

No that is not debatable. A properly rated mains input fuse would have blown preventing the transformer from melting down.

[EEVblog]

I have to ask the question:  Aside from improper use (which is certainly the case for Dave's experience) has there been any confirmed problems with the lack of a mains fuse reported from units in the wild?

Yes. There is another thread months ago on the forum, which did not get much attention at the time. 

Added link: https://www.eevblog.com/forum/repair/repairing-a-weller-soldering-station/

There is a comment on the Youtube video about someone who's unit burned down.

[EEVblog]

I don't know what all the fuss is about. So your iron spewed some smoke. So what??

If I had walked out the door after switching it on and hadn't noticed it and reacted it would have set of the smoke alarm automatically evacuating the building and calling the fire brigade. That's at a minimum.
Sure it's not Weller's fault that I plugged a 120V unit into 240V, but it is their fault for not including a mains side fuse that's defacto industry standard in competing products.

This isn't evidence that it's going to "burn your lab down".  It probably would have gone open circuit and then died. It's probably packed full of fire retardants. I don't think Weller needs to go looking for certification loopholes for a two cent part. I'm also sure they also don't want to be sued.

That's why any sensible company adds a primary fuse.

Prove that it's dangerous first. Then you can rant.

If you can't figure out how a non-fused primary can be potentially dangerous even if it is legal and common in all sorts of stuff, then you shouldn't be on an engineering forum.
Of course it's not a huge deal in practice, but it's perfectly warranted to rant about it and point it out to people so they can make informed buying decisions.
And I can rant about whatever I want on channel, you get no say in that, ever.

[beanflying]

The first video well oops I screwed up but if it had a fuse maybe it wouldn't have. That is debatable

No that is not debatable. A properly rated mains input fuse would have blown preventing the transformer from melting down.

You are saying 'properly rated mains fuse' in the case of a 110V rated appliance like you plugged in and didn't figure out that's what it is then the stock fuse it comes with will be rated about twice the current rating of the 240V one. Ergo the Transformer when powered off 240V when switched of can run at 200%+ load before something gives. A primary side fuse would certainly be the recommended and better option but not guaranteed to make it safe.

[capt bullshot]

I'm pretty sure, someone at Weller stated: Yes, that's the intended failure mode and we don't have a primary fuse for a reason. These smallish transformers fail open after spewing out the smoke, so it's perfectly safe. Then it's all about  corporate wank and bullshit what lead to the answer Dave got. Never admit to a customer that something might have been wrong with the product in the first place. Every company lawyer will strongly recommend against admitting a fail, since that will seriously impact a lawsuit that the customer might start.

And I have no doubt that this particular product passed all safety tests, so it's clearly their point to state that to "Sir" Dave. Maybe some internal action will start, but we'll never come to know about that.

So one shouldn't rant about the missing fuse (which surely would have prevented the smoke event depending on the "strength" of the transformer), but about all the corporate bullshit that's happening behind the doors everywhere today.

[SparkyFX]

No matter what my opinion is, i still wonder how they got it certified and which reasons from an electrical design point of view could explain the lack of a fuse (other than money or bad engineering). Does this somehow "justify" an existing risk? There could also be a gain somewhere. Maybe requirements of the transformer dropped, a problem with a startup condition (open load, short circuit load) or otherwise failed tests?

They obviously used to have them... i have an older Weller model here with the fuse holder right in the front panel in series to the switch and transformer.

[tchicago]

There is no such company called Weller anymore. There is some nebulous "Apex Group" which acquired Weller brand name due to a series of acquisitions of acquisitions of acquisitions. As a result, they keep manufacturing (contracted in China) and selling the legacy Weller products. There are no Weller technical people left with the company to reply to your query. All that is left is marketing, lawyers and a bunch of MBAs. They have no idea about any technical stuff, all they know is that there is a certification mark, so they are OK.
When those legacy products become very obsolete, they hire some noname oem/design company to uplift their product line, and make sure they pass through the certification. Once this is done, the oem design contract is over, and Apex just manufactures and sells boxed products, having no idea how it was designed.

[sibeen]

You are saying 'properly rated mains fuse' in the case of a 110V rated appliance like you plugged in and didn't figure out that's what it is then the stock fuse it comes with will be rated about twice the current rating of the 240V one. Ergo the Transformer when powered off 240V when switched of can run at 200%+ load before something gives. A primary side fuse would certainly be the recommended and better option but not guaranteed to make it safe.

Wait...what? A properly rated fuse is there to protect the cabling so that it doesn't, you know, burn to a crisp. In this case the primary cabling burnt to a crisp, ergo the cable had far more current through it than it was capable of handling. A fuse would have prevented this.

In this case the core would have saturated through the well above voltage and the 50 Hz wouldn't have helped.

[capt bullshot]

That's why any sensible company adds a primary fuse.

There're no more sensible companies today. At least if their primary goal is a "two digit growth".
Even HPAK does bullshit that a sensible company wouldn't, see their shiny E36312A series power supplies. This thing doesn't have a mains power switch, and the front panel power button just turns off the display while the rest of the unit still consumes a whopping 10W standby power. A sensible company wouldn't release such a thing today. At least the horrendous bug (a really large transient at mains turn on that can destroy your circuits) get fixed, but you'll have to read EEVblog forum to get knowledge about the available fix. A sensible company wouldn't just say "There's no danger for the (human) operator of the unit" but recall all the units or offer field applicable fixes.

[beanflying]

You are saying 'properly rated mains fuse' in the case of a 110V rated appliance like you plugged in and didn't figure out that's what it is then the stock fuse it comes with will be rated about twice the current rating of the 240V one. Ergo the Transformer when powered off 240V when switched of can run at 200%+ load before something gives. A primary side fuse would certainly be the recommended and better option but not guaranteed to make it safe.

Wait...what? A properly rated fuse is there to protect the cabling so that it doesn't, you know, burn to a crisp. In this case the primary cabling burnt to a crisp, ergo the cable had far more current through it than it was capable of handling. A fuse would have prevented this.

In this case the core would have saturated through the well above voltage and the 50 Hz wouldn't have helped.

So you have no problem with a fuse rated at twice the current rating on a transformer wound for 60hz and 110V being put on 240V? That is not Engineering by any stretch. With say 1 sq mm mains cable should take 10A your 110V fuse on a 60W iron is going to be 0.75 or 1A sure the cable is safe but are the windings? In the case of it having a 1A fitted your well over 200% and more like 300% power at the windings before the fuse goes.

[doktor pyta]

Another place worth closer look in Weller is the grounding of the tip.
My Weller PU81+WSP80 has the tip tied directly to mains PE.
In my case I modified it adding 1Meg resistor in series as it is done in ESD  wrist strap.

[capt bullshot]

Another place worth closer look in Weller is the grounding of the tip.
My Weller PU81+WSP80 has the tip tied directly to mains PE.
In my case I modified it adding 1Meg resistor in series as it is done in ESD  wrist strap.

Yes, bonding the tip to PE is quite annoying, but appears common today. Many years ago, I was told the "main advantage" of a proper soldering station over a simple mains operated iron would be "and the tip is isolated from PE, so one can do soldering on a live (not mains, of course) circuit". Imagine, some ten years ago I was quite suprised that with modern stations the tip is solidly bonded to earth again.

[sibeen]

You are saying 'properly rated mains fuse' in the case of a 110V rated appliance like you plugged in and didn't figure out that's what it is then the stock fuse it comes with will be rated about twice the current rating of the 240V one. Ergo the Transformer when powered off 240V when switched of can run at 200%+ load before something gives. A primary side fuse would certainly be the recommended and better option but not guaranteed to make it safe.

Wait...what? A properly rated fuse is there to protect the cabling so that it doesn't, you know, burn to a crisp. In this case the primary cabling burnt to a crisp, ergo the cable had far more current through it than it was capable of handling. A fuse would have prevented this.

In this case the core would have saturated through the well above voltage and the 50 Hz wouldn't have helped.

So you have no problem with a fuse rated at twice the current rating on a transformer wound for 60hz and 110V being put on 240V? That is not Engineering by any stretch. With say 1 sq mm mains cable should take 10A your 110V fuse on a 60W iron is going to be 0.75 or 1A sure the cable is safe but are the windings? In the case of it having a 1A fitted your well over 200% and more like 300% power at the windings before the fuse goes.

I'm sorry, I really don't understand your last.

The primary winding is going to have some basic capability rating, for example 1 amp. You would then use a fuse of say approximately 0.8 amps to protect it from burning out in the situation that Dave found himself in. Nothing to do with the voltage, or the power of the iron etc. Just a basic fuse that will protect the primary winding of the transformer.

[beanflying]

I'm sorry, I really don't understand your last.

The primary winding is going to have some basic capability rating, for example 1 amp. You would then use a fuse of say approximately 1.5 amps to protect it from burning out in the situation that Dave found himself in. Nothing to do with the voltage, or the power of the iron etc. Just a basic fuse that will protect the primary winding of the transformer.

The Base station Dave fried was a 110V unit and to get the same power out it would have say a 0.75 - 1A fuse. Plug that into Australia's 240V with the 'correct fuse' and you can pull 200%+ of the power before the fuse will let go. So 200%+ (not allowing for saturation frequency etc.) power can go somewhere before the fuse will let go.

Given a worst case of a shorted secondary or another fault the current rating of the fuse hasn't magically changed but the power available at the Primary taps has due to the increased voltage, simply more power more heat. Not saying the fuse won't beat the winding to break but it isn't good engineering as a protection device against incorrect voltage being used. Adding some additional thermal protection would change this for the better but I haven't seen it done on any Wellers?

So I am happy to stand by 'Debatable' as per my older post.

[sibeen]

You don't select a fuse for this type of application on the power rating, just the current carrying capability of the device you are trying to protect, in this case the input transformer.

[timelessbeing]

it would have set of the smoke alarm

A shitty time to be sure. At the end of the day, I think the manufacturer is mainly responsible for making sure their product doesn't cause bodily harm. But if user error causes them inconvenience... 

Of course it's not a huge deal in practice, but it's perfectly warranted to rant about it and point it out to people so they can make informed buying decisions.

Sure, inform them of the facts.

And I can rant about whatever I want on channel, you get no say in that, ever.

Of course. You can go overboard about whatever you want.

My point wasn't about fuses, or who is right. I just take issue with you saying it's going to burn your lab down, which is not substantiated.
This video has a very clickbaity, "the sky is falling" vibe to it. 

[beanflying]

So select one then for a 60W 110V iron then? You get around the 0.75-1A mark depending on the headroom you want and what the transformer can handle. Take that same transformer leave the fuse in because you are having a bad day and plug it into 240V and then what happens does the fuse blow or do the windings?

[sibeen]

So select one then for a 60W 110V iron then? You get around the 0.75-1A mark depending on the headroom you want and what the transformer can handle. Take that same transformer leave the fuse in because you are having a bad day and plug it into 240V and then what happens does the fuse blow or do the windings?

If the current is higher than the fuse rating then the fuse will eventually blow, and as the fuse is always rated to blow at a lower value than the cable current handling capability of the winding then the winding will never blow. That's the basic idea of the fuse.