Capacitors having higher ripple current before first inductor

[japlytic]

I am crossfeeding the thread from https://www.badcaps.net/forum/showthread.php?t=1000 because there is now a section for power supplies, and there was no such section when I originally wrote this thread.

In two power supplies (Wintel Win1X STB and a Centrex CTD-2100 DVD player) I have repaired, the bulging capacitors were immediately after the rectifier and before the first inductor.
Therefore, I suspect that the ripple current at the capacitor immediately after the rectifier and before the first inductor is higher than the capacitors after the first inductor.

Is this correct?

The circuits for the power supplies:
http://www.eserviceinfo.com/download..._CTD-2100.html (C20 was bulging)
http://www.eserviceinfo.com/download...tel_Win1X.html (C8 and C10 were bulging)

As I said earlier, the bulging capacitors were immediately after the rectifier and before the first inductor.

[linuxguru]

Re: Capacitors having higher ripple current before first inductor

Yes, the ripple current is higher on the left leg of the pi-filter (inner, before the inductor). The capacitor on the right leg of the pi-filter (outer, after the inductor) further smooths out some of the ripple voltage superimposed on the DC voltage, but it generally has less stress. Furthermore, the inner cap is usually physically closer to the cross-wound toroidal main inductor, which sometimes runs warm/hot. So it is subject to greater thermal stress and usually fails first. The +5v, +12v and +3.3v rails are typically the most vulnerable.

You can get away with using standard 85c, regular caps on the outer caps, but it is always preferable to use 105c low-ESR high-quality caps for the inner caps.