Capacitor goes boom... why?

I was trying to fix up an electronic device, called TurboBooster Plus. It contained a few inductors, chokes, capacitors, dual op amp IC for L+R audio output, video out and power in plus 3 more chips. An octal tri state chip, 2k SRAM (coupled with a 0.1 Farad capacitor to retain data while the main power's off) and a NEC branded AISC switching circuit to manage the SRAM content.

One of the capacitor blew up next to the AISC chip:
https://i256.photobucket.com/albums/hh198/puddle_jump/BUSTED_CAP2.jpg It left a lot of hairy residue, like a mouse crawled inside and died. Fiberglass I hope.

Looking at the trace, it just connects VCC to GND so it's probably used as noise filter to maintain clean DC power for the 3 chips. It was pretty far from where the power plugged in and other capacitors between the power plug and the blown cap all looked OK with no bulging or leakage. I do plan to replace them as it's about 25 years old and cheap electrolytes don't usually remain stable for so long. I'm wondering if the cap just blew up from old age?

The TurboBooster Plus still works... mostly as I can still get A/V but I can't get the save function to work. When I removed the SRAM, plugged it in the EPROM programmer, and ran SRAM test it passed. I can't find any datasheet on the AISC chip: D65006GFE08 68 pins IC package. I searched on Google and got lots of hit from part resellers but none of them would provide any detail or even if it's the same chip or not. For all I know some of them are using keyword spam to attract Google searches in hope of selling junk.

Capacitors can and do die from "old age" and as you've found out can go with a bang.

Its worth putting a new one in and keeping an eye on it.

I never ever power up older equipment for the first few times without the cover on or without eye protection for this very reason !

picbits said:

Capacitors can and do die from "old age" and as you've found out can go with a bang.

Its worth putting a new one in and keeping an eye on it.

I never ever power up older equipment for the first few times without the cover on or without eye protection for this very reason !

Click to expand...

This isn't really what I'd call 'older equipment' - it's normally only a concern with really old valve equipment.

The serious way that's gone 'bang' I'd be inclined to check the voltage on that rail, because modern capacitors don't survive even a tiny amount higher than they are specified for. In the older days you could happily use a 25V capacitor on a rail that occasionally hit 30V - now they instantly die about 26V

I certainly wouldn't recommend using the unit without the capacitor fitted though, it may do more damage.

Good advice.
When I die I plan to go with a bang too

If the unit has had some less-then-professional repair and the replacement electrolytic capacitor was installed backwards, it could explode.