High supply voltage, high current, bad quality. Hard to say.
The life expectancy of a foil cap depends on the voltage applied: If the rated voltage is applied it can be rather short. Maybe the high input voltage and the repetive current spikes killed the cap. After a fast rise of the input voltage (due to the leading edge dimmer) the LC input circuit could produce a overoltage. Probably the cap was a bit underrated for the circuit both in its voltage and current rating.
My guess is, the cap failed and without any capacitance the voltage spikes burned the snubber diode.
The overall quality looks good. I have seen much worse power supplies.
Hmm, the universal dimmer makes it a bit murky, as there is no indication as to what mode it runs in. It is meant to detect the type of load connected and switch between leading or trailing edge. I'll see if I can get more info tomorrow.
So one possibility is that the leading edge waveform and the resulting spikes killed the cap. That sounds like a driver design problem as it specifically says it's triac-dimmable. Is there any way a malformed waveform could have caused damage?
If the dimmer ran in trailing edge mode it should be OK then?
The quality inside does look decent. I was expecting worse before I opened it, especially after I saw the price on alibaba.
My guess is that they haven't tested this PSU properly under all conditions. If you say this and many others failed within a year while they were not even powered on each day then it should have been found in the testing phase of the product but not many companies continue to do this anymore.
Yup, only a handful remain working. Maybe I should leave one running for a month to see what happens.
This looks like an OEM bought chinese origin PSU (found it on baba for a few $ see picture) and the practice is often unfortunately that the customer does the real testing
Yeah that looks like the one. The internal build looks pretty decent for that price, unless there's a hidden cost somewhere.
If it was up to me I sent them all back to the manufacturer asking for a decent supply esp. if you paid normal price. If they ship shit let them take the consequences or they will continue to sell it.
Ahh, that's where the fun begins. The lighting company has shut down. The office management are looking into the next course of action. Meanwhile I'm just trying to find out what could have happened.
BTW: if your mains is really 252 VAC than you operated it outside the max. conditions and that could be taken as an argument from the seller. If this is really the case then the installer is to blame, he should have checked the conditions in the building with the fixtures before installing and should not have installed them in the first place.
But 252V is still within spec. I would have thought anything sold here would have to be able to handle it.
Hmm, I just checked with the UPS remotely, the voltage is now 245V. I do remember seeing 252V in the past, but unfortunately the software doesn't log the actual voltage, it just logged the extended overvoltage and AVR trim events. I'll bring my meter in tomorrow and double-check.
If thats what I think it is a CRCM flyback, that little SMA diode is part of a RCD snubber and at 100W plus conversion efficency it will see large current spikes. From the datasheet L6561
I'm doing a CRCM flyback AT 30W and Ipk is 1.8A, if you don't accomodate for propagation and switching delays you could easily hit over 2A. For a 100W converter I would guess at least three times that, so that little diode is taking a shit kicking. Should have used something like this
You have to also watch ratings for those film caps not all are equal some have serious derating for temp and frequency for VAC, VDC and Irms.
Just read this after typing the reply above. So you suspect a driver that hasn't been properly designed, with an under-rated diode and cap?
The spare driver I tried seemed to run fine when I left it running for a week, but maybe that's not long enough for problems to crop up. There was no excessive heat or any noises. I didn't test it on a dimmer though. Could the addition of a dimmer cause the issues, or could it just be a bad batch of parts, or just a matter of time regardless of dimmer?
Thanks for the replies everyone!