Fixing another Nest heat link - with easy tests
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- เผยแพร่เมื่อ 6 ต.ค. 2024
- This appears to be a common fault with these units. If your heat link fails out of warranty it may be an easy fix to get it going again.
Here are some simple tests that can be done on an unpowered unit to check that the rest of the circuitry is still working.
Note that in the UK our boiler (furnace) control systems are usually 240V. In a way it might be better to adopt the American 24V system. Especially since electrical training standards have plummeted due to the activities of a financially motivated "voluntary electrical safety" company.
All equipment associated with a heating system should be fed from just one circuit. Adding on other sections powered from other circuits can energise an isolated/disconnected system randomly via the control line.
These units have been educational. I really like the use of two different electrolytic capacitors in parallel. As well as being shorter than a single high value capacitor, if one is later found to be prone to drying out, the other will keep the system running. Likewise the use of two diodes in series means that if one fails short circuit the other will keep the system running. The small extra cost of these extra components is massively dwarfed by the cost of a warranty return/repair. Especially when the unit has to be replaced by a technician.
Note that the primary suspect component for failing is quite tricky to remove due to having a heatsink pad underneath. It is much easier to remove with two soldering irons being used as improvised heated tweezers.
If you have doubts about desoldering and replacing the diode, then don't risk damaging the PCB. There are eBay sellers offering a fixed price repair service for these units.
I wonder what replacement component they are fitting in the warranty exchange units.
The original is an S3100. The one I used is a B360B - which is rated 3A and 60V. I can't guarantee that this is a perfect replacement. A diode rated 3A or higher and 100V or higher is probably a better option. I've since found out that the original package is called a Powerdi.
Once I've got and tested some others in I'll add the stock numbers here.
If you enjoy these videos you can help support the channel with a dollar for coffee, cookies and random gadgets for disassembly at:-
www.bigclive.co...
This also keeps the channel independent of TH-cam's advertising algorithms allowing it to be a bit more dangerous and naughty.
#ElectronicsCreators
Hi Clive. I had my heat link fail a few weeks ago. Following watching both your videos, I searched the Internet and found a few people saying talking to Google support, they had been given a replacement.
I did that yesterday, and Google pretty much instantly said they would make an exception and have it replaced, even though it was out of warranty. I followed the link they emailed me and got a service visit next day to replace the unit via a company called boxt.
The engineer said they had a contract from Google to replace any faulty unit, and there was a team of engineers doing this.
Maybe you could sticky this to your video as it helped me get a free next day replacement.
Thank you for your service...
Thanks Adrian your input helped me get an appointment for a free replacement 😀
@Basil Hoult excellent! Glad it helped Basil.
@@adrianscarlett Many thanks, just got my 3 year old heat link replaced and fitted free of charge!
Just came here to make the same comment. 😂
My 2 year old unit just failed, I remembered watching Clives vid a few months ago, so came back to it, thinking I might fix it myself…. But got in touch with Google support and have Boxt engineer coming tomorrow for a free replacement.
Seems as though this is a common fault that they are fully aware of and willing to put right, but only if you chase them.
@adrianscarlett who/how did you contact? I've got a problem with mine they always tell me to contact my "Local Nest Pro"
I have seen this before. When I was a project manager for a large electronics manufacturer we started getting a lot of boards back. Basically the manufacturer to save money has stopped individual testing of the diodes so about 200ppm were way below spec for reverse bias voltage. IE 1000V diodes that sort of worked at 200V or sometimes only 100V. When you are shifting 50,000 units a month and each board has 17 diodes in mains circuits that's over 2000 early life failures a year from that one fault alone.
Ugh, at 200ppm, your need to continue individual testing. And it wasn't that the past were a little bit of of spec. It would be different if those diodes were only a little bit of if spec.
Similar story to yours, but on the customer side.
I worked as a maintenance/reliability engineer for a chemical manufacturing plant that was only a couple of years old. The plant had this newfangled switchgear full of coms buses and microcontrollers, where traditionally hardwired relays and motor protection units (e.g. Multilin 369) would have been used.
We had many, many failures of this "smart" switchgear, costing us millions in lost production. After lots of "robust discussion" with the OEM, it was finally revealed that we weren't the only customer experiencing these failures and they had traced the problem to faulty SMD capacitors in the coms cards. Turns out the capacitor manufacturer had a bad batch of capacitors that somehow passed QA and wound up in all sorts of consumer goods and industrial equipment.
The switchgear with the faulty components was either entirely replaced or, where viable, had the coms cards replaced. To the best of my knowledge there have been no further failures in the past ~5 years.
I really liked the part with tips for quick diagnostics. It's a real engineering approach to problem solving optimization, respect! 👍
Timestamp?
Nest Tech Support ... "Hello, This is Clive"
Yeah, um, hi; I need help troubleshooting my nest.
Okay, I'm gonna need you to grab a voltmeter and prime your soldering iron while we take it apart.
@@BradTech. "also a reminder to use lead free solder." Clive: "Oh piss off ill use whatever I like"
A Good job again well Done
That's ace from you Peter Stevens 👏
😂😂😂 waiting for the takedown notice
This video gives me the confidence to try to fix it myself. I bought my heatlink second hand, so trying this will be fun and learning something new.
Thank you for sharing.
Just a quick story. I'm still using my Antex Model C 15W precision soldering iron which was bought around 1972 to build a Sinclair Mini Radio receiver. Great bits of kit!
I had the same issue with my Heat Link. Before ordering a replacement diode I decided to contact Nest. I bought my Nest 2,5 years ago so officially it is out of warranty, but they proposed to replace my broken unit with a new one for free. So that's great service!
Thank you for the tutorial on surface mount components, I just need to practice at them I think. That USB port is also used for pulling diagnostics and doing a factory reset if needed, I've had to do it on a few Nest thermostats over the years.
@tech 52 Yes, appears as a USB drive.
Just to mention: be careful with reducing the secondary diode voltage in flyback converters, because in forward turn the voltage in the secondary is usually 3-5 times higher than the nominal. The diode should withstand the sum of the nominal and forward voltages.
I ended up retrofitting both units with higher voltage rated diodes than the originals. I've never really thought about the higher voltage when reverse biased.
@@bigclivedotcom Depending on the circuit you can run into all sorts of weird issues. EG one you probably know is that diodes keep conducting for up to a few microseconds after you reverse the polarity on them. 1N series are pretty slow and FR1007 make a good alternative and have the same form factor. Then there is the lesser known slew rate issue. IE conduction starts with just a single atom and spreads out fast. If the slew rate is too fast for the silicon to conduct properly you can blow a component at 10% of it's rated current. This is a chuffing nightmare in mm wave radars belting out 50kW+.
Dont forget to tweak the flux capacitor too!
>;o0
@@garrygemmell5676 or flux “capacitator”, as an infamous reporter once said. 😂
@@bigclivedotcom Yeah have to worry about the reflected voltage from the primary. Although to get an exact value he turns ratio is needed. Basically the total reverse voltage is the (primary rail voltage / turns ratio) + secondary voltage. Almost got burned by it myself when designing a modest 60W flyback. Totally forgot about it when I went to order the diode for the bootstrap circuit. Fortunately I remembered as I was assembling it, and had a suitably rated Schottky in the parts bin.
My bf could easily repair our Nest HeatLink thanks to your helpful video. He used a VS-30BQ100 diode. It is slightly larger than the pads, so he had to be a bit creative. But it is working now. Thank you for your video!
I can't thank you enough. I got my Nest link working and this was my first time using a solder and fixing electronics. It took a while to find a proper diode but i managed to find a LT8582 from some old tv box i had in my attic. Much appreciated.
If the diode failed due to ESD, that could be the fact that they chose a Schottky device.. They tend to be much more sensitive to ESD than conventional rectifier diodes, so possibly an argument to just replace the diode with a regular 1N4000 series.. I once ruined almost an entire package of axial leaded Schottky diodes simply by taking them out of the package by hand, grabbing on the leads.. Originally thought I got a bad batch and called the supplier and he asked if I used ESD precautions before unpackaging.. It turned out that that particular diode really did not like ESD. Once in-circuit it was fine, but needed to be handled very carefully when installing.. This was the one and only component that I have ever had ESD issues with.. I remember the early days with CMOS 4000 series chips where everyone was initially paranoid about ESD, but never ever blew one of those (well ok, I may have killed one inverter out of a hex chip once, but it may also have been because I connected power to the output, but regardless, I had 5 other nverters to use on the chip, so I don't count that)..
My first repair used a UF4003. The high speed version of the 1N400X series.
Yes though the only CMOS gates you really had to worry about were those with no protection diodes, generally those that were used as timers, as they made the diodes in those very small and with a high series resistance, so that he clock inputs could exceed the supply rails. That and some did come without ESD protection for special purposes, generally the unbuffered ones. Going to bet the diodes you blew were ultra low capacitance type, the honking big power types generally survive. These diodes on the Nest likely are simply from overloads and shorts on the output side, and also from having to charge up the low ESR capacitors in the circuit on power on.
2 capacitors are to make sure there are no resonances in the capacitor near operating frequencies, so different types of capacitors from different manufacturers, so that the ultra low ESR one can handle the high frequency spikes and the other simply filters out the ripple from that.
Yeah same thing here, I always take at least light precautions for it but I've never ever had a problem with it and so I always think that it's a pointless task
With this power going external to box, additional ESD clamping diodes on the 12v rail wouldn't go a miss here. Even with a good install the 12v is still quite susceptible to ESD failures.
@@SeanBZA - in an old 1980s designed SMPSU sold under Farnell’s own name (but not designed by them I don’t think), the secondary uses three electrolytic capacitors. Two of one make and one of another make. Also one is an axial type. One reason is as detailed in the post above, the second is to have a lower ESR than if a single capacitor was used (keep in mind that these were almost certainly normal electrolytic capacitors, as I’m not sure low ESR types existed back in the mid-1980s) and lastly, to keep the height of the board low so that it could be squeezed into the case.
I barely understand what's going on here but I love it! Repairing stuff is good!
I had the same problem, my thermostat/Heat Link is already a while out of warranty. I fixed it with this video, so a thank you is in order.
Thanks for both videos on these. I installed a Nest thermostat my self a month back. So if the heat link ever stops I will know to check this Diode now.
Going back a few years when I was involved in such stuff, two components in series (diodes, resistors etc.) was also a common way of ensuring passing certain safety certification testing where they check shorted components don't cause flame/mains creep to low voltage connectors etc. as they only checked for single component failure not multiple simultaneous. Don't know if that's still a thing now but thought you might find that interesting.
Bringing up the Antex (once or twice lol) made me smile - I've just ordered some tips for my trusty XS25 - they've changed them (I have had it about 30+ years!) No more clip or split - a kind of corrugated heat transfer linear spring inside now. If it last 30+ years, it'll probably outlast me.
Many thanks for the video big Clive. I’ve just fixed mine using this method.
I know nothing about this stuff but the video and comments are fascinating.
Such complicated things spoken of as easily as how to pour milk.
Remember, when you replace your old thermostat with one of these, keep the old thermostat somewhere so when the new fancy one dies you are just a simple change from having heat again.
Or just keep the old thermostat and not spend the money.
@@sparkledragon6216 better idea
Even better, install the old one in a temperature sensitive area, such as near the plumbing, set lower (say upper 50s F to low 60s, or 10-15c, as an automatic emergency backup to keep your pipes from freezing.
However, when I had two NEST thermostats in a box (not this one, the actually thermostat control), and the one on the wall had batteries that welded themselves in AND had green creep to the board (thank you alkaline, and a thermostat that never said the batteries were dead), putting a NEST in place was a no-brainer. I didn't have to drive out to install it, and had enough time after doing so to identify that it wasn't the thermostat causing the heat to be out, and call a tech to figure out the real problem. Before it became VERY cold that night.
In this application, make sure to use a robust RECTIFIER rated diode - there is no particular need to have any type of "fast" of low forward voltage diode here. In fact fast diodes can be the cause of higher EMI in case of inductive loads, relays, etc. Remember that diode is likely to see 3x ~ 8x + the nominal supply voltage depending on the length of wire run to the unit - that power supply wire is going to appear like an inductor when load is switching or during surges.
The other fun thing that happens is if the wiring for these units (on power supply or load side) runs parallel to any power wire feeding an inductive motor - maybe a fridge, heat pump, AC, fans etc. Strong inductive coupling all over. You will see all sorts of power hash hitting these units, especially when a nearby heavy load switches on or off. It gets really exciting when the installers run wiring for delicate equipment like this in a steel conduit alongside heavy power circuits - now you have several one turn transformers inductively coupling everything together inside the conduit. Makes no difference if twisted pair / shielded wiring in use or not - you're talking about many random near-field coupling going on. That's why that diode needs to be very robust - and it's surprising they chose surface mount device. Using the PCB pad as a heat sink only helps slightly. Real thru hole diode package and a small size real heat sink would stand up to much more abuse. That's why we don't use this NEST stuff.
@@captainmother1268 Even better if the thermostat wire is run near a fluorescent light fixture, or three, or five...
You do need a fast diode, as it is the output of a switchmode converter so you are dealing with more than the usual 50Hz. However, it doesn't have to be schottky.
as usual I enjoyed your video...It may be a bit over my head and Prolly will never do it...but, i enjoy your videos just the same. Clive, thank you for all the time you commit to your channel!!!
How did I ever satisfy my electronical curiosity needs without you.
This is great news clive! if you give it back and they use it give us an update in the future please! it is good news though that its the same problem. at least if mine goes out of warranty its probably going to be the same issue. so ill probably attempt to fix it AT MY OWN RISK of course. better than spending near £200 for a whole replacement system!
It could be because that diode is connected to an inductive load, when it is switched on and off, that relay might see a huge spike in voltage causing an avalanche current that is frying it. It could be that newer solenoids/valves have an integrated flyback diode and this is only a problem when retrofitting to older installations with old solenoids/valves. Might be useful to pick a replacement diode meant to withstand a high reverse voltage
Some time people simply forgot or ignored the fact than solid state relay (diode induced) is not the best option for inductive load. I have a client ignored my advice on a SSR for an inductive load and proceed to deliver the machine to their client. For the past 6 months, I got 3 paid service jobs for replacing the dead SSR. I'm not complaining, hopes I get more paid service jobs in the coming month.
@@auwy7828 mechanical relay can have issues with inductive loads as well. use a flyback diode where possible. if switching a solenoid and speed is a concern, use a clamping diode to limit the maximum voltage to below the breakdown voltage
The diode was in the Power supply section, hence there was no regulated voltage on power up. Any inductive load such as a solenoid on the load ( contacts) side of the relay would have to breakdown the relay insulation to influence the coil side voltage, unless I am missing some other mechanism at work?
One of your best videos for viewers comments. Some excellent content and interesting reading.
Big thanks for your videos just had the same problem with my heat link second time it's happened first time under warranty so this time I fixed it see how it goes
Top man Clive as always. I have only had problems with the receiver thermostat as a 'Sparky'
8:35 Cliveilocks and the Three Diodes. "The first diode was too big...and the second diode was too small...but the third diode was just right!"
I came to the comments section just to see if I was the only one to think this
I've now got the original diode package style on it's way.
This product is one I would avoid because my thought is "one strike and you are out". Life testing and a good thorough circuit review as well as in-coming test of components should eliminate these types of failures.
Thanks for this video! This really helped me fixing my own nest heat link! I had the same problem and it is solved now!
Big thank you!! Same issue here, replaced the diode and were back online 😊
Hello, did you install the same diode from the video? b360b
Merci.
Big man with soldering irons in each fist! Watch out!! Seriously though, I enjoy your channel very much! Wishing you all the best.
so glad I saw this video months ago my heatlink has just failed with this as the probable fault the device powers via usb and then links to the thermostat but doesnt do anything else.
Great video, small correction: In the end you said that putting two diodes in series would've halved the number of returns, but assuming an equal failure rate and one failing not influencing the other, it would actually reduce the returns by a factor of the failure rate. This will potentially reduce the returns by a lot more than half. For example, at a 1% parts failure rate over the lifetime of the device, you would only get only 1 in 100 of the original returns 🙂
Brilliant video really enjoyed this and all of the repair information!
Many thanks Clive
If you have the money, Weller sells tweezer irons that go in their higher end 12V stations. Absolute lifesaver for removing stuff like that diode.
Thank you so much I managed to do this fix my diode was to big so I had to cut the back but worked anyway👍
Oh, the joys of replacing SMDs! How my ugly mitts do love 0201s.
The US Nest is a significantly different design. The power Is 24v ac and has a logic circuit to help the installer correctly identify W (heat), G (fan), and Y (cooling) to the equipment. The equiment interface is very sensitive to ESD and fails often during install.
My problem with surface mount parts is my hand shakes too much. That is why i retired from ac repair.
Really enjoy a good repair video 👍. I guess you have identified a product fault. Shame that so many of these devices will become ewaste due to this fault, as like you said in previous nest video, a repair engineer will probably just replace the entire unit..
Love this fix, same happened to me last year and my mates this Xmas
Btw: if anyone is frustrated that Alexa can turn the heating off but won’t turn on the heating… 6 months to discover this command, you say
Alexa set heating to heat
I presume same command with other AI devs
Alexa, set heating to heat
Alexa turn the heating to heat
Once you’ve done either of those Alexa will apply her grammar algorithms and you can say it like
Alexa turn the heating on
It's interesting that this is connected to mains power. In the US, a residential thermostat would have a 24v supply from the furnace/air
I got concerned towards the end as you had mains hooked up and started pointing around with the metal screw driver, I was expecting this to end electro boom style 😂
Glad the two iron trick worked for you.
That's part of the reason why that diode that you replaced in the last video is rated at 3A - the 12v output that you tested for short can supply power to the Nest thermostat itself which obviously has wifi, screen, backlight, processor so that + both relays in the heatlink would take it over the 1A, possibly significantly over if you were powering 2 thermostats...
Interesting and very helpful diagnostic test info with the meter/power bank for when mine dies 🤣
You've got realy good at fixing these, You should start a one day course to make teenagers into heating electricians. :)
Also really easy to fry the HVAC unit's main control board if the wall thermostat is not hooked up with the power off. A guy at work did that once. He was an excellent electrician, just not experienced with low voltage. I remember it was a pretty expensive repair.
The original diode is available on ebay uk, from memory £5 each. Also available from Aliexpress for something like £5 for 5
Do you have a link for this please ?
@@jamesasprey2092 Just search for PDS3100
the other fix using THT stuff to annoy the SMD parts around it, was more to my liking :D
Two soldering irons, great trick.. why i never thought of that...
It would be interesting to hook up an oscilloscope and check diode reverse voltage at start up and during as many operational transient modes (load changes) you can think of.
What I got out of it was flux on solder braid pulls up solder *better*. I needed that info.
Mouser part #: 621-PDS3100-13, diodes, from Mouser look identical to the faulty ones you removed
In basically all European countries, except Britain (out of the EU but still part of Europe), we use 24 VAC because it is just a little bit more safe and reliable. Disadvantage of 24 VAC is the relative high idle power consumption. There is alway a small 'traditional' transformer dissipating heat, usually somewhat around 4 Watt.
I wasn't aware that other European countries used the 24V too. It makes sense.
@@bigclivedotcom In Germany and the Netherlands you will find a lot of components from Danfoss, this brand is the de facto standard. You might also encounter brands like ABB, Honeywell and Nibe. They all use 24 VAC 50 Hz. The more south you go in Europe you might see components from French and Italian origine.
Thank you for showing them test methods ill have remember them. :3
Paralleled caps of different makes can be redundancy, but it might also be to get the ESR or physical size into a suitable range. I've seen designs where you use a bank of small ones to make the capacitance a flat package, to get a nice and low ESR, and/or to even out the stress over multiple components.
Dual irons! this has to be a first for TH-cam :))
I am surprised that Clive wasn't holding them both in the same hand!
@@richardturton6900 Soldering chopsticks
Definitely *not* a first for TH-cam as I've shown it. Although one of mine was a soldering gun so it might not technically count as an iron.
Clive, a certified Nest repairer
two diodes in series would be a good fix!
Amazing how something so small can be the cause of the failure.
Actually it's the other way around. The smaller you make stuff the more amazing it is they actually work.
It's always the little ones which end up growing into a big pain in the butt, am I right? 😅
@@BradTech. same with kids
For want of a nail, the shoe was lost. For want of a shoe, the horse was lost, for want of a horse, the rider was lost..... All for the want of a nail.
It's not a new concept.
The chip you pointed at, MXIC branded, is a flash ROM, probably SPI, maybe dual or quad SPI. Likely storing the firmware that the processor runs.
"Extra juicy" luvv it , it is what makes your vids unique that East Kilbride sense of humour - Well you really need it if you live in The Murray or Greenhills, you got out in time BIG C! Poor old JVC in Glenburn road gone, Motorola gone, Munro Healthcare gone, even the old bowling alley up Stroud road is gone i worked in em all ...it has become a sad old place EK now only redeeming feature is a rather "juicy" poundland in the Olympia centre!!
I've had 3 of these not work
I think you have uncovered a massive broken hardware conspiracy haha
Smart thermostat failure has frozen pipes & flooded a few houses in the neighbourhood. In these cases, it was depleted batteries.
I do wonder whether the two different kinds of capacitor in parallel has something to do with the ESR characteristics of the two different caps? Like perhaps they need a certain amount of low-ESR capacitance for spiky loads, but they still saw some low-frequency characteristics that went away when they added the additional bulk capacitance. Since it's not high-frequency, they can save a couple of cents and get a standard-ESR capacitor.
It may even be cheaper having two separate capacitors rather than one larger, higher-capacity low-ESR capacitor. In which case the design engineer's boss can go to management and tell them he saved the company a few tens of thousands of dollars across the product's entire run, and take home a nice bonus.
Of course, that's before they would've had to replace all those units due to the dodgy diodes. But I'm sure he would've pushed for the value engineering of that part too, not to mention taking credit for saving money on it.
Our design engineers would only specify the low esr caps if absolutely necessary as they were more expensive and added 3the design costs!
Had mine for 3-4 years and it packed up on Monday
One in USA use 24v not 220v
Ac get 120v or 220v n sent 24v to thermostat n only 3 wires one wires to heat n one wire power 24v n one wire cold
Ac have maid pcd boards that have reply requires 24v to kick it on n sent power to it
I surprised you knew what was wrong with it n amazing troubleshooting experience
Cool video as ever thanks for the quality stuff
Don't overlook pre-warming the board using a domestic hairdryer on hot for a minute or two before desoldering components like this. Start desoldering immediately afterwards (no delay)
It reduces thermal shock as well as helps desoldering the lead-free solder.
In mass production if there is a weakness in one component, it will affect thousands of gadgets nor machines. For instance if you have a model of a car with say near side window winder broken and go down to the scrap yard to get a replacement all that models of that car will have window winder missing as every one wants one.
Like the VW EOS on Salvage Rebuilds UK channel this evening!
Clive I have an ESP32Cam which... makes noise. It sings. I swear it does. Physical sound. It has no components that make sound. It's 100% solid state. Nobody believes me. I videoed it. People said it was the camera focusing, but it's a solid state camera, no focus. So I removed the camera and tried again, videoed it again and ... it still made the sound. Processor noise. Almost musical. I figured with some clever C programming we could get it to play a tune. If I was to hunt it out of the junk pile, verify it STILL makes noise, could I send it to you for independent evaluation? I'm not BS'ing WooWoo, history channel, I infact expect it's magnetic coupling on the "can" over the main chip that is causing this particular ESP32Cam to resonate (it's can) and make audible sound.
Probably don't want to replace the diode like-for-like as it appears to be intolerant of voltage transients and dies too easily. 1N4007 are pretty bombproof and would probably make good replacements. You can even get SMD versions of them.
1N4007 is not suited to the frequency of operation here, hence why I used the UF (ultra fast) version.
@@bigclivedotcom Ah, good point. I forgot it was on the back end of a switcher.
Little red riding Clive went into the empty _nest_ , the 3 diodes had gone. On the table sat 3 bowls of porridge. Clive first tried daddy SS36G diode's bowl.. it was too big! Clive next tried Momma PMEG6030EP's bowl.. it was too small!
Sighing in frustration, Clive finally tried Baby B360B's bowl. It was juuuust right.
...
Sorry Clive I just could not resist. :D
Cheers,
Thanks from Texas Clive
I am literally fitting one now
This is what I was talking about when you repaired the last one Big Clive. In my opinion, the SMD diodes just don't seem to be as robust as the through hole diodes. Maybe I'm Wrong? These two diodes going bad certainly are not enough evidence to backup what I'm suggesting.
A big relay or contactor will put a high reverse voltage on the system. It usually finds the weakest component fast. Good job! Sell it cheap! Good luck.
I’ve had two heat links fail this past week on separate jobs. Seems to becoming more common. Luckily on these occasion Google sent out replacements.
I was thinking about getting a nest or similar device to control my heating and hot water in the future so I can turn it on and off from afar. I might reconsider but I can at least perform these kinds of repairs so I don’t think me having one will cause me much headache.
You can never predict what the external load will be. You can specify but these specs. are often overlooked. So a good designer should provide a complete compliment of circuit protections.
nest repair centre!! great
Goldilocks and the Clumsy Bear - This diode is too big, this diode is too small, this diode is just right.
Hi Clive, Aways enjoy watching your videos. Njoy coffee. I have a dead Aldi car battery charger. I can't seem to fix it. Would be nice if you could fix it and do a video. Regards Arvind
Very interesting as always bigclive, and thanks for your input.
Do you know if the original users of these two units were using the 12v externally or not? I have the nest installed at home but do not use that 12v circuit, i set it up just switching the boiler contacts.
I am curious in your opinion, would using, or not using that 12v output have any difference in the expected life of that diode?
Regards.
There is a possibility that the external wiring on the 12V supply may have exposed the diode to static.
Mine died a couple of weeks ago, not using the 12v circuit :(
@@stuartmcguire7416 Mine died about a year ago - still in warranty, so google swapped it (replacement was here withing 48 hrs - and they offered to pay for someone to fit it as well).
Symptoms were the heatlink unit completely dead - will never know what it was, but these diode switches do look to give the symptoms I saw. Like you, I wasn't using the external 12v - thermostat runs on usb and just relies on radio to connect.
Be interesting to see if the 12v circuit feeds some of the internals - I presume yes.
I'm getting two more of these devices. I hope they dont fail quickly.
Clive, superb 2x videos on the Heat Link Failure, Mine just failed, same issue, 14 months old, Google replaced it within 3 days. I will repair the old one as a spare, would you be able to confirm the diode you finally decided to fit to be more resilient than the original. Keep up the great videos, Many Thanks.
cpc.farnell.com/diodes-inc/pds5100-13/schottky-rectifier-powerdi5/dp/SC17545
Out of stock right now, but there are other diodes that will work.
Thanks Clive, much appreciated, enjoy the coffee :-) Kind Regards, Dave.
I got that yellow iron too ... my firs one. It was horrible but it worked. Let me see what mine was branded as. Think it was 17-19W
It is rather unfortunate that the Diodes incorporated "PowerDI5-3" package is the same as a TO-277 package, is rare compared to the slightly larger TO-277A. Without a caliper on hand, I am not sure the more common package would work in this instance.
B360B was the Goldilocks capacitor (and the clumsy bear)
If I have a beer I can solder SMD like a pro. Now give me a cup of coffee and all bets are off 😁
- Could the spike from the relays turning off be killing that diode?
- Another thing is that the relays are responsible for the majority of the load taken by the power supply. Could the transition from “on” to “off” be causing a poorly-designed feedback network to misbehave and throw the voltage into the diode’s breakdown voltage area?!
All the options I can think of, however, stem from the assumption that something is inherently wrong with the circuit design, and not its use.
Cheers!
yet again the same culprit! interesting... either a recall or better diode supply for free from the manufacturer will do :)
Yes the two soldering iron rework trick ;)
Clive, not criticism, but a pencil eraser might hold small objects for soldering, and usually aren't affected by casual soldering.
That MXIC looks like a NOR flash, you could dump out its content with RPI or ch341
What does the output from the diode feed external to the Nest box?
If the 12-volt output from the Nest box feeds anything inductive or capacitive, is there any back EMF/Flyback diode fitted across the 12 volts output of the Nest box to prevent spikes from coming back into the Nest box, thus damaging this diode? It may be worth just fitting a diode across the 12 volt output just in case this is the cause of the SMT diode going short, a back EMF/Flyback diode will certainly do no harm if this isn't the cause of the diode in these Nest boxes going short.
Just a thought........
K Watt.
You know what they say about guys with large hands?
They have large problems soldering surface mount components.
Mine failed this week with this issue. The thermostat unit in the living room is powered independently so there would have been no chance that this would have caused it.