Power supply capacitor replacement (was: Dead capacitor?)

Picture says it all..



Could I have screwed up how to put it in or do they just die like that?

Cheers,
B:

They can do that when old or overheated.

But do check that it isn't in backwards, or getting hot somehow.

I'm asking also because of this:
http://en.wikipedia.org/wiki/Capacitor_plague

and because it's neither hot there nor are they old (well, installed at least - got them in a kit from ppa). I'll replace it anyway, but I'd still like to know what's what, because if others from the same kit may start to fail, I'd rather be prepared.

http://home.teletu.it/APPSI/APP%20studio%20PSU2%20schematic.pdf

Here is the schematic -- the bulging/dead capacitor is C15. I don't have a 100uF 50V, however I do have a 1000uF. Can I place it there anyway?

Hi All,

this cap is faulty, but it is an high quality components made by SAMWHA (Korea) that is one of world leaders in capacitors.
( http://www.samwha.com/templatedirs/guest/acom_capacitors.html ) .SAMWHA is used in several high level hi-fi products and it is weel known for its quality. To be clear it is not a cheap/unknown components.  

Moreover this cap is the SAMWHA RD series (not the standard series), that is the high temperature series (105°C) and, moreover, it is rated of 63V when in my PSU it work at only 35V max, and at 40°C max. In these condictions this cap work with very high margins, but also an high quality components can be defective, this is the matter.

BTW, there are several PSU's inside uncheap gears that are not the same quality of the components I use in these kit.  

I have sold more than 100 kits and these PSU's work fine without problems. There are several PSU's that work from a year without caps erupted  .

I am going to send you another cap to replace the wrong  
 

this is the cap datasheet for reference http://www.samwha.com/electric/templatedirs/guest/list_pdf2/RD.pdf






 

Hi ppa,

thanks for explainging; I am a beginner with these kinds of projects and am sorry if description of my problem offended. It's also good to know that the rest of the capacitors shouldn't fail. It's worth noting that the circuit worked well for quite some time before one day I put in more modules than I had in there and it died with a flash. The PSU still worked when power cycled.

That said, I'm looking forward to the replacement capacitor, but I have a session soon and could use the equipment powered by this PSU. Do you think that I could temporarily use a 1000uF/50V at this spot?

Cheers,
B.

no problems, just to be sure who read know that I use not bad components inside my kits.

C15 is used only to reduce the ripple noise at the negative out, so the power supply can run without it without problem but with more noise,

if you want replace it with another cap you can use a cap from 4.7uF to 2200uF with >= 35V of voltage.


cheers
Pier Paolo

baadc0de said:

one day I put in more modules than I had in there and it died with a flash. The PSU still worked when power cycled.

Click to expand...

Is there a chance that something short circuited? Positive rail to negative rail? Does that kind of thing damage a PSU output cap, PPA?

One failure mechanism that can damage a capacitor like that is a shorted rectifier diode. If instead of DC, the diode is driving the full transformer secondary AC into the capacitor it can easily overheat.

JR

edit- disregard... my comment only applies when cap is used as smoothing reservoir in PS, not on output of regulator. /edit

if the main negative voltage out is shorted to the positive out than this cap can have an reverse voltage so it can be damaged. When there is this short circuit the LM regulator with the bigger current limit give a reverse voltage to the out caps of the other LM