Pop!So, I was sitting trying to figure out why an EHX Super Space Drum (which I was repairing for someone else) wasn't working.
All of a sudden, I heard a loud pop, like somebody claps their hands once, right next to your ear.
It was really loud and felt like it almost started ringing in my ear.
Of course I had no idea what it was and got really scared I had blown something up in the EHX thing I was repairing, because it wasn't mine...
Though, I suspected it was the power supply, because .. what else could it be? It sounded like a capacitor blowing up. So, I switched it off and continued my repair using my other power supply...
When the EHX thing was done I opened the suspected power supply and looked inside.
This is what I found just laying on the bottom...
|Yes, it's empty.|
What was that?
Where did that come from? At the time of the explosion, I was using one of the variable channels.
By the way, the power supply is called PS23023 and here's what it looks like:
|Photo from http://www.velleman.eu|
I looked inside, trying to find a blown capacitor.
After a little while, I found this...
|Now there's your problem!|
|I noticed a few stains that may be electrolyte, so I cleaned a bit, but it didn't seem to be much.|
Mystery solved! This was the fixed +5V board btw, not for the variable channel I was using at the time...
So, it had just blown up spontaneously.
Note the markings on the other cap: "40/085/10". I believe those markings mean that it's rated for -40C to +85C with 10% tolerance. Interestingly enough, ALL the other caps I could find in there were +105C grade. I googled around a bit and found the manufacturer for these.
I found another interesting post:
"A capacitor in a power supply exploded. It is 2200uf 25v. I attached a photo of the other side."
The attached photo shows a cap that looks exactly like the one I have.
So in this power supply, for some reason, they had chosen cheap Chinese crap caps rated lower than all the others, as reservoir capacitors for the fixed +5V board.
Though I think more of the caps on the board were from (the same?) Chinese manufacturers, I didn't really check all of them, but I did note they were supposedly 105C, which was good enough for me.
- Ningbo Zhengming
Actually, avoid Chinese capacitors overall, if possible...
I don't know what they do; just rate them higher than they are, poor production, crappy quality control... all of the above?
Who knows. Just google "Chinese capacitors" and enjoy the results :)
Fixing itWhen looking at the board, it turned out those two caps were just connected in parallel, acting as one big capacitor. Anyway, I had to fix this and I wasn't going to order another pair of no-name crap caps.
I'm going Japanese on this! My local retailer didn't have any better alternatives for 2200uF than 50V.
I decided to replace both the busted one and the survivor, since I guess it was just a matter of time before that would blow up too.
I bought two Nichicon 2200uF 50V and put there instead.
This is what it looks like now:
|Check out these puppies!|
I've had the powersupply switched on a few hours since replacing the caps and nothing has exploded yet :)
Hurrah for another successful repair!
Booo for another case of Chinese caps exploding.