PCB Component Repairs

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Fail to dead-short is a common failure mode. It happens when the substrate of the cap cracks. The layers are so close to each other that any failure in the dielectric leads to a short and then in designs with enough short-circuit current, a pop-corn failure where the cap explodes.

My understanding is that it’s often stress from either board flex or residual soldering stress. Automotive rated and high-reliability ceramic caps often use soft layers in their terminations to avoid this. They also sometimes have the opposite electrodes pulled back somewhat from the termination region so that a crack propagating from the metallization area is much less likely to pass through a section with both electrodes in it.

I’ve run into discussions about this a lot because it gets much worse with larger body ceramic caps and we use a ton of the TDK C5750 size (5.7mm x 5.0mm, 2220 size in ‘imperial’) which makes a lot of auto guys very nervous. Turns out there’s a huge difference in mechanical strength between class I and class II dielectric caps. You can cause a value change in a big X7R cap by dropping it 100mm onto a desk. I’ve never been able to break one of these large C0G caps even on a board flexed into a taco and hit on the back side with a hammer.

Nothing that I could see. No obvious physical damage or marks on it.

Yeah, I’ve seen my share of electrolytic failures but not really in more modern equipment. I think if you’re dealing with commodity equipment from the 80s-90s it may be more prevalent but I think those failures brought the issue to light and resulted in people learning how to avoid it. It’s a lot more common to see well specified lifespans on datasheets and companies that I’ve worked for have rules requiring the calculation of lifespan under operating conditions and the use of 105dC/high lifetime caps where possible.

I think back then there were also a lot more electrolytics doing everything whereas ceramics have gotten much better, higher capacity and cheaper so that there’s often one or two in parallel with the electrolytic which helps a lot with mitigating the ripple current which is the actual cause of the lifespan issues with electrolytics.

Hopefully. The unfortunate thing is that I can’t really test it fully. It’s such a stark failure mode that I’m 99% sure that’s going to be the issue but the true test will be once it’s back in operation.

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Fascinating. How long did all that take you do you think?

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Somewhere between 1 and 2 hours. That wasn’t super efficient, either. It was spread over a few days and with a couple of delays due to things like forgetting to take a charged thermal camera battery home. The fluke thermal cameras are great but their battery management is apalling.

It’s basically the perfect scenario for something like this. Single obvious failure of a common component with no secondary failures.

That actually brings up a great point, this is exactly why I love dealing with well-designed electronics. They have clearly put effort into making the power supply behave itself even under fault conditions. That’s not remotely as common in cheaper/AliExpress level designs. They seem much more likely to just detonate under a fault condition which then makes it even worse to repair because the initial troubleshooting shows the damaged power supply, so you replace those components and it just detonates again, which means you need to effectively solve 2 problems at once. It’s usually still possible to power the down-stream stuff from a more robust external supply like a bench power supply or even just a better wall-wart until you get that sorted but it can be a real pain in the rear, especially if you’re not 100% sure what the rail voltages actually are…

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You are awesome. Really!

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Agreed!

Original Post:

I suspect you got way more value here from Jono in a fraction of the time, but if the quoted service would have been anything close to what he did it would have been a bargain!

Super impressive diagnostic work.

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Thanks!

Yeah, absolutely. I definitely wouldn’t begrudge them that fee and wouldn’t be surprised if they had ended up being able to do something similar. Their initial diagnostic fee sounds pretty fair. This could have easily turned into a 10-20 hour odyssey with nothing to show at the end if there were secondary failures or something nastier like the micro had been damaged, though, which is why it’s such a struggle to recommend someone try to have something repaired, sadly.

Fundamentally, it’s next to impossible to make a business case for repairing things when there’s a good chance of ‘no repair’ being the outcome. That’s why right-to-repair stuff is so important. Having schematics or a repair manual available would have made this way easier. Having firmware and flashing tools available would make it way less likely to result in nothing. Having a requirement to provide these things and longer warranty terms makes it more likely that money will be spent on making the design good and fit-for-purpose in the first place etc.

A guy can dream, I guess :slight_smile:

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I share that dream!

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My mind is a bit overloaded at the moment! Just wow!

None the less there are a lot of take-aways from this and I’ll see if I can unpack them:

  1. first and foremost a very big thank-you to @jono035 of course. I have learned much, the least of which is that pretty much all of this is so far above my pay grade that had I attempted the diagnosis, I would have certainly failed and thought a lot less of myself! :wink:

For me, that is the most important aspect of this exercise. Yes, I would have replaced the entire fan, but not before quizzing you guys on the possibility of making a new controller out of separate components each of which could be understood by me! I am thrilled that the fan is still in operation, not so thrilled that a tiny failed component could have been an end to its useful life.

I agree entirely, in fact had the $300 express fee not been part of the deal we may not be having this conversation. Our local “TV” repair guys have a similar service their diagnostic “deposit” is $200.00 which is offset against the cost of any work done and helps with the “no repair” situation - given that most of the work is in finding the fault I don’t have a problem with that either - they too have a very long lead time.

I am preparing a document for BigAss Fans (in this case, with your permission, quoting some of your diagnostic text) requesting that they do just that once they cease holding stock.

Note that had the board been in current stock, they said they would have provided a replacement at no cost as a matter of “good will”. Their policy seems to be what one would expect from a supplier of premium priced product.

This, and a number of other comments made during our discussions have made me feel a bit warm and fuzzy. There’s a bit of cognative dissonance happening in justifying my purchase of course, but I am really happy to support any company that puts in the effort to manufacture a great product - notwithstanding that the price has a premium attached.

In the long run, this means fewer purchases of replacement machines. It doesn’t always work like that, but the build quality is equally excellent as it should be in what is a very expensive ceiling fan (with light).

In summary - thanks so much @jono035 , I’m so in love with the process that I (almost) don’t want it back! Seriously, this has been a fantastic exercise for me and your usual super clear and comprehensive description of the process have added another layer of icing on an already very tasty cake!

:kissing_heart: (man kisses)

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On the contrary, I think you’d have ruled out the obvious easy stuff and then it would have been part 2 of the discussion. Aside from the thermal camera aspect, there’s nothing here that I would have done differently or suggested that others do differently. Admittedly getting the SMT cap off the multi-layer copper plane was a real pain in the ass, so that was probably a 7/10 on the soldering difficulty scale. Then again, I also refused to turn up the iron out of fear of damaging the board, so maybe turning it up to 450C would have gotten it off instantly.

That’s how it always goes, though. It’s very seldom that something big and important just dies outright, it’s usually something small, random, overlooked etc. The entire thing is fundamentally lots of tiny components!

Go nuts! And yeah, absolutely, step 1 is good warranty support, step 2 is availability of spares, step 3 is opening of documentation to allow repair once the first 2 steps outlive their usefulness.

There was an issue with the earliest model of Nissan Leaf where the on-board chargers had a bunch of different ways they would fail. Not enough to be terrible, but enough that it was an issue. The first process was warranty replacements by Nissan. The second process was replacement with wrecked parts, which is what I did. The final process has been that I’ve completely reverse engineered them and written a comprehensive repair manual for a local company that specialises in EV repair and they’re one of only 2-3 places in the world actually repairing the broken ones (not just swapping bits in and out) and fixing a bunch of the known issues as they do.

And that’s the thing. Sure, if it breaks and I can’t repair it then they’ve got the chance to sell me another fan, but if it breaks and I CAN repair it because they’ve provided the tools to do so, you better believe that they’re going to sell me every single fan I do buy for the rest of my days!

I think I said this above but I think the problem is that we’ve gotten very comparative with how we see pricing. It’s ‘how much does this cost vs this other thing’, without having any insight into the actual lifespan/design/externalities of the product itself. It’s much harder to look at something and go ‘absent other information, is this a fair price to pay for this product’.

Personally, I think that there should be rigorously enforced legally required warranty periods that match the expected lifespan of a product, not just 1-2 years. Suppliers should also be liable for the fully circular end-of-life of the products they make/import. If your product is half the price because it has a 4x higher failure rate then there’s no way that makes business sense. Fundamentally, this would be cost-neutral to consumers, too, because things would be more expensive up front but cheaper overall due to them not failing. And fundamentally MUCH cheaper because we wouldn’t be taking on this insane level of environmental debt by racking up carbon emissions and depleting our scarce resources by continually making cheap short-lifespan crap that ends up in landfill.
Bleargh.

No worries at all, I was pretty keen to get an up-close look at it and so far I’ve liked what I’ve seen. I even got a couple of ideas from it like a better way to do soldered wire-to-PCB connections by using a crimped pin-terminal and soldering that in instead of the wire directly.

:blush:

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I agree entirely with the whole paragraph here. I once posted a photograph of a bicycle that had been fished out of our lake, barnacle encrusted etc. I noted that some basket had stolen it and merely dumped it. A friend from India could not believe what he was seeing: “Bicycles are for life” he replied.

And they should be, but here they are “until the tire goes flat.”

Another positive outcome of this thread is that it put me in touch with our local Repair Cafe - guess who is lobbing up at the next session to lend a hand?

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Awesome! Let us know how you get on, I should have a look around for something like that locally.

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So many products get tossed before they finish their expected life. A lot of people would not want to spend double on something that they won’t keep for 4x the time.

Of course, we always think we will use something for a long time. But that just doesn’t happen in business or personal use for things.

Something like a ceiling fan is categorized as a “durable good”. Because they are supposed to work until they break, and then be repaired. Cars, washing machines, etc should all have replacement parts available for a long period of time (10 years, at least). But I wouldn’t expect to pay up front for a warranty for any of them for 10 years. That would cost a lot more than the original device. I doubt any company would agree to doing the white glove repair you just did. You’re awesome.

That’s all a distraction though. This repair was very entertaining and it is great to see someone helping someone else because they have the power. It reminds me of getting the serving dish from the high shelf at my grandma’s house. Your skill and goodwill are appreciated.

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Here in New Zealand we have the Consumer Guarantees Act that requires that things sold are of ‘acceptable quality’, which is defined, among other things, as being safe and durable. It’s written such that the lifespan must be what a ‘reasonable consumer’ would expect.

This is only for sales to consumers but it can’t be contracted out of and supersedes any statements such as standard warranty lengths.

It’s one of the reasons I encourage people to buy EV charging cables from local suppliers. Originally they were all the same crap quality coming in from overseas and lasting a year or two. The difference being that the local suppliers honour their requirements under the CGA and provide repair/replacement for cables that fail in that time. Over the past 10 years the local suppliers now all still source their cables from overseas because we sadly don’t really do that level of manufacturing here, but they’re all their own specifically modified designs now and are much more robust/fit for purpose.

Exactly, which is why I think it shouldn’t be an option at all, which is admittedly an extreme position to take.

A more moderate version of that same position is that I don’t necessarily care how long things will last, as long as the end-of-life costs are priced in. We have a local charity that dismantles a wide range of products down to parts that are economically viable to recycle. For some things they don’t charge a fee, for others they do, depending on the value of the raw materials that can be recovered and the time/hassle it takes to recover them. From talking to one of the guys who runs it, they’re in the high 90% range for actual recycling of certain parts of products and actively looking for ways to improve the rest.

They charge $20 for an inkjet printer, lead-acid car batteries are free, power tool batteries are something like $5/kg, power tools are free, PCs are free, white goods vary from free to $5-20 ish. etc.

What I’d like to see is an agreed range for recycling costs and then anyone selling that item is required to charge a fee for that recycling up front. That money can go into a central fund and get paid out to people who collect and recycle such products to an acceptable standard, all audited of course. That way it becomes actually financially viable to recycle a product and divert it from landfill, which makes it zero cost to dispose of that product correctly and even allows things like kerbside pickup for certain situations. When it costs $20 to recycle a printer, you see them in the general garbage or dumped out on the side of the road all the time. If it cost $0 and you could just drop it off at the local hardware store, collection center or even kerbside pickup then you’d see a LOT less stuff getting dumped.

The problem is that most people want to spend as little as possible on a thing. The cost of the item is more than the sticker price, it’s the sum of ALL externalized costs that we don’t effectively account for. It’s also the social and environmental costs of the raw material extraction, refinement, manufacture, shipping, storage, sale, EOL collection and disposal. Having as many of those costs priced in is the ONLY way that I can see to combat the ‘cheap shit from China’ effect.

Anyway, that’s my soap box rant for the day :slight_smile:

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I agree 100% with @jono035 above, but would also add that, the issue of tossing things before their expected life adds enormously to this problem and pressure on the world’s resources.

If products were designed to have a VERY long life, they would have a value at the end of a short period of ownership. Even if that value was minimal, and someone picked up the item and used it for a second “short” period - that will double the use of the resource.

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Progress over the last seven days:-

Happiness is knowing that “tomorrow” (last Friday) your repaired PCB is going to arrive and all will be well with the world.

Frustration is “today” (last Thursday) when your doctor, after removing a skin cancer from your shoulder, casually suggests not stretching the arm in any direction till the stitches are out.

Despair is when, three days (Monday) into the seven you are waiting for the stitch removal, you get some wild flu bug, that means you have to delay getting them out another three days.

Hope is what keeps us going till next Monday, when we’ll publish actual photographs of the results of @jono035 's handiwork!

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Oh shoot.

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All good (except the fan’s not fixed!) - the flu is sad, the skin cancer par for the course when you reach a certain age and you’ve lived a life outdoors in Aus - I just feel a bit sad for @jono035 because it’s taking me longer to do a five minute job than it took him to diagnose, repair and send the thing back across an ocean! :smiley:

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Yeah, NZ too. It’s crazy how that’s just the normal situation for us down here. Everyone just reaches that age where they start getting core-sampled once every few years to try to stay ahead of it. Hope it’s all good.

Most of the rest of the world just doesn’t get it. It’s wild. UV index of 14-15 during summer, burn times in the single digit minutes.

As I said before, don’t mind me, I’m just stoked it was such an easy fix. Take all the time you need to recover. I’m trying to convince one of the guys at work not to work from home with covid and to actually relax and, you know, recover! Plenty of time for fan testing when you’re up for it.

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It’s hilarious - heavily overcast today index is 11 at the moment. “Core sampling” is a great description - all is good, but an annual checkup is part of the routine as well as retina scans.

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Colorado has the highest rate of skin cancer in the US. The elevation means we have less atmosphere blocking UV and we still get a lot of sunny days.

I am very conscious of it with my kids. Slip, Slop, Slap is from Aus, I think. But we practice it a lot all summer (less strict about hats in the winter).

It is a pretty treatable kind of cancer. But cancer still sucks. I hope you feel better soon.

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