EEVblog 1481 - Dodgy Dangerous Heater REPAIR

A heater that doesn't heat up should be an easy and quick repair, right? RIGHT?
This Arlec space heater also has a rather dodgy and product recall worthy dangerous construction!

00:00 - Arlec space heater
03:20 - PRODUCT RECALL TIME!
05:12 - Heater element measurement
07:31 - PCB inspection
11:31 - Verifying the fault
12:50 - Relay bypass
13:21 - Thou shall measure voltages
15:00 - Diode bridge
15:48 - Gotcha!
17:34 - Parts salvage time
18:48 - Jaycar visit
20:49 - Mains capacitive divider
23:02 - X and Y class capacitors

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#ElectronicsCreators #Repair #Arlec

[AndyFletcherX]

The cable trapping is a product recall job. If you feel enthusiastic then send photos and report to the big box store. Their lawyers will then trip over each other in their attempts to avoid liability by issuing a product recall.

[nicwilson]

18:58 Oh that is a beautiful sight! A proper electronics store that sells actual component...we lost all of ours in the UK so now the only option is order online and pay shipping :(

[sysghost]

If there's something I've learned with all these EEVBlog videos, it is that my uncle is named Bob. And that stuff is flapping in the breeze.

[buddysnackit]

What I like about you Dave is that you show your mistakes. It was understandable and gives your videos a "real" feel to them.

[gnif]

I literally repaired an Aldi electric blanket controller last week for my parents that had the exact same failure, and used the exact same larger part. Had to explain to my dad why it was important we use an X class capacitor instead of another with the same rating from his parts bin. Sunbeam are also notorious for using capacitors that are under-rated on the voltage to ensure death of the device (you will need to google this, great writeup on it but YT yeets my posts if I put a link in them).

[derekloudon]

As per Nic's comment, we in the UK have lost all our "walk in & drool" electronic component stores 🩲 I used to love walking into Maplin and browse for ages getting ideas (my wife was very tolerant as I am when we visit a wool/craft shop). Yes, we buy on-line but it's not the same. Walking around looking and touching the components can often change the direction of your project (usually for the better).

[KGE]

In the Netherlands we call this capacitance loss 'the Senseo Syndrome' because almost all Senseo coffeemakers suffered from this problem. I can not count how many devices I sent for repair within the warranty period (!) When older than two years (aka out of warranty) I just replaced them myself. I lost count how many :-)

[ZylonFPV]

19:10 - Dave destroys an entire line of JayCar’s caps

[dentakuweb]

Repair videos of very simple electrical appliances like this are a good way to explain what the jellybean parts you see every day do. Big Clive has pretty much made it his job.

[ThriftyToolShed]

I had a Kill-A-Watt meter that was reading incorrectly due to a similar failure. Replacing the cap was the fix for sure and I have a video of that repair. I was surprised how expensive these X rated caps are and like you mentioned it's best to keep boards around for parts. Like you I did not have the exact one on any donor board. It's sure handy when donors work out! Great video.

[theraiderra]

I love repair time!
Difficult to repair most things nowdays with everything being integrated into one chip... but you always learn something.

[zaprodk]

The x-class caps do not blow up, but it's quite normal for them to lose capacity as the wear mechanism. The metallisation on the foil is slowly eroded away.

[fabiotrevisan]

Great repair video there Dave, as usual I should say, but as you went through, you referred to that 47R resistor there, several times as a "dropper resistor" and, as though we can't say it's wrong (all in all it's in series and indeed "drop" some voltage), this IS NOT its intent on this kind of circuit.
Sure enough, it's meant to be an Inrush current limiter, to prevent a high current peak when the "dropper" capacitor is discharged and you happen to connect to the mains while it is at the peak voltage.
As it turns out, the impedance of the capacitor, being a 220n @ 50Hz, is around 14.5 kOhm so, a 47R resistor can barely drop anything.
On its turn however, maybe this resistor being so small can be exactly the explanation why the capacitor failed, because being so low in value, the inrush current on the capacitor will be gigantic.
It could have been very well of 10x its value, and the inrush current would still be some 30x the nominal current.
Granted, 470R would drop a little bit more voltage and would maybe require a higher power rating resistor, but would be a little bit more sane.

[aerobaticant]

Hi Dave. I've seen many failures of capacitors in this type of circuit. Particularly on the control PCB for my central heating boiler. Also in a Philips branded LED night light. As soon as you said the relay wasn't energising, the series capacitor was my first suspect! I wish we still had electronic component shops like Jaycar here "back in the Old Dart" :-)

[MomirPeh]

I'm suspecting that it's a metallized film cap and it has self-healing properties when the dielectric fails. The self-healing is going to do its thing by burning off the metallized film in the area where the dielectric has broken down and it will no longer be a problem and the cap will continue to be a cap. But, the capacitance will go down slightly due to the metallized film area that was lost in the process. That particular cap seems to have suffered a lot of such events and it has lost a lot (roughly half) of the electrode area... I'm wondering how that cap looks inside now :)
BTW, I've had these caps failing in such way in a lot of the equipment that uses it for either filtering or as the dropper component.
Edit: I didn't watch the video to the end when I wrote this. :) Dave did mention that it's a self-healing cap...

[greengrayradio]

The series cap has had a breakdown caused by a voltage spike, healed, and now has a too low capacitance to drive the relay. It has done its job as a safety X2 component

[brainndamage]

I saw this exact failure a lot. Most commonly in PIR motion sensors, and even in a plug-in mains power meter. I suspect they use lower-voltage rated caps and label them as higher voltage. They work but are right at the edge, and over time voltage spikes will destroy enough foil to make them go bad. You can also see that a properly rated X2 cap is a lot larger for the same capacitance and voltage.

[bloodybucket]

I've got a 'not'-dehumidifier in my basement that's getting a second look-at this weekend.
Thanks Dave.

[zebo-the-fat]

I love the high quality metalwork in this product!

[Stoneman]

We bought a European brand name panel heater with a similar form factor to the Bunnings number, and it work a treat (they are really good heaters IMO) for about four or five years before failing. After a bit of troubleshooting it turned out to be the supercap that provided the power to store time, timer and what not settings that had failed. Once replaced it was good as new and is still going strong three years later. Winner winner!