Jackcon Capacitors Jacked Off In My Woofer.

[Muttley Snickers]

I’m currently in the process of setting up a dedicated computer for audio and music applications and yesterday I hooked up a set of surround speakers which had been sitting around in a box for nearly a decade, I wanted to see if they were going to be suitable for my application and remember setting these up and testing them out years ago but never really had a use for them. The system incorporates a nice 8 inch active subwoofer, four surrounds and a centre all of which are in reasonably decent cabinets, my intention was to just use the active subwoofer along with a front left and right as I don’t need nor want the additional surround channels.

Anyway, I connected everything up and made sure the volume pots were turned down then switched the power on to the subwoofer and to my surprise heard a loud thump followed by a constant humming and then a hissing, I quickly went around and checked all of the connections and everything appeared to be in good order, then all of a sudden the subwoofer started to spew out copious amounts of smoke from the two front vent ports. I quickly disconnected all of the cables and then transported the speaker outside assuming that it had caught fire and was still burning or smouldering internally.

The amount of smoke generated by this thing was extraordinary to say the least and it completely filled the room in only a few seconds and continued for ages even after the power was disconnected. Once outside I quickly removed the rear panel and noticed a large thick sheet of wadding which I pulled out and checked to make sure it wasn’t burning, after further inspection it turned out to be nothing more than a couple of nasty Jackcon branded capacitors which had let go and jacked off all over the place. Busy with other things I haven’t started to fix this yet and will probably need to use my Weller Pyropen to de-solder and lift those existing capacitor leads on the rectifier board as I doubt any of my other irons will be up to the task. It is the two 35 volt 4700 uF caps which appear to be the problem but I will probably take them all out just in case.

[Andrew]

"Jackcons Jack-off Jatons Junked"

Sorry, the alliteration wrote itself. 

[TERRA Operative]

Yeah, pull them all and replace the lot.
Use a reputable brand and the thing will last for another decade or two.

[edpalmer42]

I don't think this is your typical 'bad capacitor' story.

Bad capacitors fail because their high ESR and/or low ripple current rating cause them to wear out while operating.

In this case, capacitors which had sat, unused, for a decade, failed on power-up.  Any electrolytic that has been sitting for a decade is vulnerable to this kind of failure.  The effective voltage rating of the capacitor slowly drops and if the applied voltage is too high, the capacitor reacts the same as any capacitor that is subjected to a voltage greater than its rating.

Capacitors that have been sitting for years can be restored to normal by 'reforming'.  Basically, you apply rated voltage through a resistance that limits the maximum current to a few milliamps.  Wait until the current stabilizes at a very low value and you're good to go.

I haven't seen any discussion on whether typical 'bad capacitor' brands are more likely to suffer from this problem, but it wouldn't surprise me.

Ed

[Bashstreet]

Good old Jackcons nightmare of many repair techs 

[cvanc]

Good old Jackcons nightmare of many repair techs 

Agreed.  Terrible brand.  Change every one you find.