Why did this A4000 PSU just explode? [video]

Starglider 2 · 17 December 2019, 02:03

Um hello. So, on the advice of someone, I tried changing the fuse in this A4000 PSU. It had previously stopped working (quietly) when someone plugged it into a 240V supply (because it's a 120V US model).

I took out the 250V rated 5A fuse and replaced it with a 250V 5A fuse. Then this happened...

[ Show youtube player ]

As you can see there are multiple failure points.

I have one question. WHY?!!?

aeberbach · 17 December 2019, 02:35

Could the fuse have survived long enough during that 240V connection to damage parts downstream, causing the next connection to make a more spectacular failure? That's my guess. 240V applied won't kill the fuse instantly - especially if the fuse is "slow-blow" as you often find in power supplies - will have a 'T' not a 'F' in the part number. It may be impossible to tell now but that 8-pin device could have fused internally, making it a lightshow waiting to happen.

Starglider 2 · 17 December 2019, 02:42

Quote:

Originally Posted by aeberbach

Could the fuse have survived long enough during that 240V connection to damage parts downstream, causing the next connection to make a more spectacular failure? That's my guess. 240V applied won't kill the fuse instantly - especially if the fuse is "slow-blow" as you often find in power supplies - will have a 'T' not a 'F' in the part number. It may be impossible to tell now but that 8-pin device could have fused internally, making it a lightshow waiting to happen.

Actually I think that's exactly right. Darn it. And I think that would have been impossible to diagnose in order to prevent it. So I guess I don't feel quite so bad now.

Nightshft · 17 December 2019, 02:42

Hi Peri,
I second what aeberbach says. Replacing the fuse was nothing wrong (the fuse parameter 250V doesnt really matter in this case, it's just some kind of max voltage for the fuse). Also think parts got damaged before and on 2nd connection they blew up.
That's a real cool video of magic smoke escaping by the way!

Starglider 2 · 17 December 2019, 02:44

Quote:

Originally Posted by Nightshft

Hi Peri,

I second what aeberbach says. Replacing the fuse was nothing wrong (the fuse parameter 250V doesnt really matter in this case, it's just some kind of max voltage for the fuse). Also think parts got damaged before and on 2nd connection they blew up.

That's a real cool video of magic smoke escaping by the way!

Haha well at least I got something cool out of that hot moment. It's a shame as I really wanted to fix the power supply, but I guess my original hunch was right ¯\_(?)_/¯

Jope · 17 December 2019, 08:03

Time to deviate from the factory lines and go SFX with it. :-)

pipper · 17 December 2019, 08:53

Houston, we have a problem. ;-)

AmigaHope · 18 December 2019, 08:47

I question why C= went with a 250V 5A fuse in the first place. There is no way the A4000 PSU could be legitimately drawing 1250 watts, not even instantaneously. o.o; Clearly the original fuse did not die fast enough to save the downstream parts. Also was I that somebody? =P

17 December 2019, 02:03	#1
Starglider 2 Registered User Join Date: Jan 2014 Location: California Posts: 1,146	Why did this A4000 PSU just explode? [video] Um hello. So, on the advice of someone, I tried changing the fuse in this A4000 PSU. It had previously stopped working (quietly) when someone plugged it into a 240V supply (because it's a 120V US model). I took out the 250V rated 5A fuse and replaced it with a 250V 5A fuse. Then this happened... [ Show youtube player ] As you can see there are multiple failure points. I have one question. WHY?!!?

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17 December 2019, 02:35	#2
aeberbach Registered User Join Date: Mar 2019 Location: Melbourne, Australia Posts: 423	Could the fuse have survived long enough during that 240V connection to damage parts downstream, causing the next connection to make a more spectacular failure? That's my guess. 240V applied won't kill the fuse instantly - especially if the fuse is "slow-blow" as you often find in power supplies - will have a 'T' not a 'F' in the part number. It may be impossible to tell now but that 8-pin device could have fused internally, making it a lightshow waiting to happen.

17 December 2019, 02:42	#4
Nightshft Registered User Join Date: Mar 2018 Location: Austria Posts: 617	Hi Peri, I second what aeberbach says. Replacing the fuse was nothing wrong (the fuse parameter 250V doesnt really matter in this case, it's just some kind of max voltage for the fuse). Also think parts got damaged before and on 2nd connection they blew up. That's a real cool video of magic smoke escaping by the way!

17 December 2019, 08:03	#6
Jope - Join Date: Jul 2003 Location: Helsinki / Finland Age: 43 Posts: 9,880	Time to deviate from the factory lines and go SFX with it. :-)

17 December 2019, 08:53	#7
pipper Registered User Join Date: Jul 2017 Location: San Jose Posts: 667	Houston, we have a problem. ;-)

18 December 2019, 08:47	#8
AmigaHope Registered User Join Date: Sep 2006 Location: New Sandusky Posts: 943	I question why C= went with a 250V 5A fuse in the first place. There is no way the A4000 PSU could be legitimately drawing 1250 watts, not even instantaneously. o.o; Clearly the original fuse did not die fast enough to save the downstream parts. Also was I that somebody? =P

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