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Smoked Power Supply (kinda like smoked salmon; smelly)

Posted by JonathanWever 
Smoked Power Supply (kinda like smoked salmon; smelly)
April 19, 2021 02:15AM
Hello RepRappers, (almost feel like dropping a sick beat),

I have had my A8 Clone for 4 years and printed hundreds of hours. Finally, I believe I somehow fried my power supply. Hopefully my thoroughness (longwindedness) anticipates questions more than it scares away readers...

Specs:
- Alunar M508 Kit
- AC 110/220V (set to US 110V)
- DC 12V
- Bed power supplied by MOSFET
- 12V heating element in E3D V6 clone
- 12V PC fan cooling PSU
- Custom PSU mounting bracket (PSU sits horizontally and of course collects lots of dust, "yikes" now that I think about it...)

Happenings and occurrences:
- My printer had been sitting plugged directly into the wall (was not plugged into a surge protector as it usually is) with the switch powered off for a few weeks as it usually is during busy college semesters. I have used it a little within these past few months.

- Earlier the same day as the incident, my apartment experienced a brief power outage, lasted 30 seconds or so.
- Roughly 2 hours later I set up to get a print going and flipped the power switch "on".
- If I remember correctly I believe I heard my printer power on, noticeable by the sound the heatsink fan turning on (if I recall correctly).
- My PSU fan did not immediately spin to life like usual, but jittered a little in place, possibly made a small unusual noise, maybe a little whining.
- Not thinking anything of it, I spun the blades manually to get it up and going (pretty sure I would have spun it in the "correct" direction), but it did not maintain any powered rotation.
- Almost immediately after that, I saw light-grey smoke emanate from around the top and front side of the PSU - the side closest to all the wiring - from between some perforations in the metal casing and the gaps in my printed mounting bracket.
- "No-no-no".
- As soon as I saw the smoke I pulled the C13 power cable out of its respective port to the PSU.
- All this must have happened in a matter of less than 5 seconds.
- I went back after a couple minutes (probably waited that long because of pure shock, pun intended [though thankfully didn't actually shock myself tongue sticking out smiley]) and scanned the exterior with my basic IR temperature gun and found a temperature reading of 2C higher than room temp, again, at the front side near the wiring.
- I checked the power switch fuse, external to the PSU, looked fine.

That's what I gathered and that's about all I know. My lingering suspicion is that the combination of the power outage and the direct-wall power connection has something to do with it although dust is a possibility as I doubt I've cleaned the PSU and fan within a couple years. The power outage explanation doesn't make a whole lot of sense to me. The printer was off during the outage, circuit into the PSU open.

It's up to YOU to help me find out the issue. Only YOU can help prevent printer fires. I want YOU for U.S. [3DPrinterTroubleShootingHelpAssistance].
I.E. how do y'all interpret this issue and how should I go about investigating it?
I do not presently have access to a multimeter (nor the time to investigate during these last couple weeks including finals) but can investigate fully when I return home and I would appreciate any help I can get.

Supporting pictures:
- Main view: shows overall setup; PSU bracket has lid removed.

- Fan top-down view: red sketch highlights where I *think I remember* smoke coming from.

- Wiring top-down view: shows my general wiring setup. Has worked gorgeously for the couple years since I last modified it. Yellow sketch highlights roughly the location of the +2C temperature reading.
[cdn.thingiverse.com]
- Power cable view: C13 power cable with dramatic focus on wall plug.
[cdn.thingiverse.com]

Thanks for anything.
-Jonathan Wever
Re: Smoked Power Supply (kinda like smoked salmon; smelly)
April 19, 2021 08:08AM
It was probably a cheapo "LED power supply" with little to no protection and no safety certifications. It's anyone's guess as to why it chose that particular moment to fail, but if you got 4 years out of it and it didn't burn your house down consider yourself lucky. The good news is that it's cheap and easy to replace it with a quality supply. Look for a MeanWell supply (not a fake meanwell supply) that is sold by a digikey or Mouser electronics or similar commercial supplier. It will cost $5 more than another "LED power supply" from ebay but it won't fail for no reason at all.

Why do you have a fan mounted on the power supply? Are you operating the power supply at or near its spec limits? If so you might consider getting a higher spec supply. Operating anything at or near its limits is asking for trouble.
If the supply manufacturer thought a fan was needed they'd have built one in. Of course, a lot of the "LED power supplies" sold on ebay have fans, but I think their primary purpose is as an indicator of imminent failure- if you ever see it spinning you have a few minutes left in the life of the power supply.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Smoked Power Supply (kinda like smoked salmon; smelly)
April 19, 2021 08:46AM
This style power supplies has a thermal overload resistor RT1 in series with a fuse.

I had one burn up, an after replacing the thermal overload resistor RT1 power supply came back to life.
I selected a thermal overload resistor RT1 to allow for a little more current and heat before blowing.
Four years later my power is still working supplying power for my 3D Printer.

The THERMAL RESISTOR RT1 shown in the photo below.



Computer Programmer / Electronics Technician
Re: Smoked Power Supply (kinda like smoked salmon; smelly)
April 19, 2021 09:25AM
Thanks, I'll look into this.
Quote
Roberts_Clif

Edited 2 time(s). Last edit at 04/19/2021 09:36AM by JonathanWever.
Re: Smoked Power Supply (kinda like smoked salmon; smelly)
April 19, 2021 09:30AM
Thanks, I'm most likely going to get a new PSU so those suggestions help.

Why the fan? I don't believe I'm running at spec limits but a friend recommended it in my younger days and I was concerned about it heating up. I don't recall what temperatures it was running at though, but I can definitely check its specs and my printer demands.

Quote
the_digital_dentist

Edited 3 time(s). Last edit at 04/19/2021 09:36AM by JonathanWever.
Re: Smoked Power Supply (kinda like smoked salmon; smelly)
April 19, 2021 09:34AM
How much current are you pulling from that power supply, and how much is the supply rated for? Consider the current spec to be like the red line on the tachometer in your car. You wouldn't run the engine continuously at red line unless you didn't mind replacing the engine. Don't run your power supply at red line either, unless you don't mind replacing it.

Replacing safety components in a power supply is an "interesting" idea. In old houses in the US the fuse boxes had (some still do) Edison type sockets for fuses. The fuse looked like the threaded part of a light bulb and it had a glass window so you could see if the fuse was blown. Once in a while someone would get the brilliant idea to replace a blown fuse with a higher amp fuse- no more blown fuses! In some of the sockets, you could actually put a penny in the socket and then screw the blown fuse in to hold the penny in place. Others would put in a wad of aluminum foil and screw the blown fuse in to keep it in place. It worked great, sometimes for years, until the overloaded circuit burned the house to the ground.



You know, you could replace that fuse right above RT1 with a wire jumper and never have to worry about it burning out... I would never recommend it, but you could do it...

Edited 2 time(s). Last edit at 04/19/2021 09:38AM by the_digital_dentist.


Son of MegaMax 3D printer: [www.instructables.com]
Ultra MegaMax Dominator 3D printer: [drmrehorst.blogspot.com]
Re: Smoked Power Supply (kinda like smoked salmon; smelly)
April 19, 2021 09:15PM
Quote
the_digital_dentist

You know, you could replace that fuse right above RT1 with a wire jumper and never have to worry about it burning out... I would never recommend it, but you could do it...

The fact is that is exactly what I did, Though I too did not want recommend it. Have repaired electronics most of my life I knew the fuse would be enough for safety.
Still kept my eye on it for the longest time..

Edited 1 time(s). Last edit at 04/19/2021 10:33PM by Roberts_Clif.


Computer Programmer / Electronics Technician
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