When capacitors go bad...

LeeH · 01-30-2009, 06:33 AM

I picked up a Klipsch Promedia 2.1 sound system from Goodwill. Turns out it's inoperative... what a shock. It looks like several capacitors in the amp/subwoofer are shot.

Does this usually happen because the capacitors are bad, or is it caused by some other component going out?

Is there likely further damage or if the caps were replaced would it probably be ok?

Jim Richards · 01-30-2009, 06:36 AM

My memory is a bit fuzzy, but I think most bad caps tend to fail as open circuits. If so, other components might not be fried. Replace the bad caps, and fire it up.

T77911S · 01-30-2009, 07:02 AM

i have seen the big caps in the bosch cd units open and short.

why do think they are bad, oozing spooge out or what?
are they in the power supply?
unless you know electronics or see anything else burned, i would just replace and go for it, chances are everything else is ok.
can you post a pic or schematic
caps can dry out and go bad just from age.
i bought a set of EV pa speakers, one had a bad crossover. the coil for the horn shorted, no visual sign. very unusual

dhoward · dhoward's Garage

+1 electrolytic caps go bad from age.
Replacing them is usually pretty cheap. Just observe polarity to prevent large bang.

LeeH · 01-30-2009, 08:30 AM

Yep, pretty good sized caps and stuff oozed everywhere. From what I read, that can be cleaned up. Is there a good place to buy individual capacitors for cheap?

T77911S · 01-30-2009, 08:53 AM

sounds like power supp.
try parts express if they do not have it let me know, i have some places bookmarked on the other computer or post the vaules and i will help u look.

Blanco · 01-30-2009, 03:20 PM

local radio shack or frys.

slodave · slodave's Garage

I fix plenty of computer motherboards with bad capacitors. It's easy, cheap and usually fixes the problem.

A lot of times, when a capacitor goes, the top will "pop" and a dark liquid will ooze out and harden, much like old alkaline batteries.

Get the specs off the old capacitors and start calling your local electronics stores. Radio shack may carry them, but a good mom and pop electronics store would be a better bet.

T77911S · 02-02-2009, 05:10 AM

Quote:

Originally Posted by Blanco

local radio shack or frys.

radio shack is a joke. i went in one not long ago, not sure how they stay in business. i even think there is a thread here saying the same thing.
its easier just to order.
how is it going?

ruf-porsche · ruf-porsche's Garage

Mouser

gt350mike · 02-02-2009, 09:10 AM

Quote:

Originally Posted by ruf-porsche

Mouser

Mouser is a great choice (they're owned by my former employer, TTI Inc.). Digikey is another source of caps.

Most of the engineers that I called on switched from a standard Aluminum electrolytics caps to what they call a polymer aluminum cap because they will withstand higher temps almost 2x as long. If you going to go through the trouble of replacing the old cap, use these.

Here is the link of a company (United Chemi-Con) that has been selling these for several years.
http://www.chemi-con.co.jp/e/catalog/pdf/al-e/al-all-e1001i/al-conductive-e-080829.pdf

You will have a choice between surface mount (PX series, starting on p.29) or thru-hole (PS series, starting on p.41). If you have trouble finding the correct part number, just post the value that you need along with the rough deminsions of the cap you're placing, and I should be able to generate a part number.

Not sure if Digikey or Mouser will have what you need in stock, but you can always call a distributor (Arrow, TTI, Avnet) and ask for samples.

HardDrive · 02-02-2009, 11:55 AM

Quote:

Originally Posted by T77911S

radio shack is a joke. i went in one not long ago, not sure how they stay in business. i even think there is a thread here saying the same thing.
its easier just to order.
how is it going?

Radio Shack has went nearly totally consumer electronics, but I'm still damn glad they are around. Their selection is limited, by they typical have the stuff you would need for repairs. In many rural areas its them or ordering online.

Schumi · 02-02-2009, 12:13 PM

Here's what happens on a lot of lower grade audio equipment (yes, even some Klipsch)..

They skimp on the capacitor's rated voltages, so you see, say 63V capacitors a lot of times in the power circuits. Now this is normally fine, as you might have a toroidal transformer that takes 110V to 43V and that 43V AC is rectified into 60.6 volts, which is less than 63V so your caps are ok.

But try checking your outlets with a multimeter some time. A lot of times, depending on a lot of factors like how old the transformers outside your home are and how clean your town's poer grid is... it will not be at 110V. A friend recently had caps fail in a Klipsch powered subwoofer. They were 63V caps running after a 110/43 toroid. His wall voltage was 132V. This puts the input to the caps at around 72 volts, which is more than the 63 volts the caps are rated for, and they start smoking like burnt popcorn.

This is why those high end audio people buy power conditioners. SISO. (Sh$# in, Sh&$ out). You can't expect your audio equipment to sound perfect when the power from the wall is dirtier than a Thai hooker.

T77911S · 02-02-2009, 01:49 PM

Quote:

Originally Posted by HardDrive

Radio Shack has went nearly totally consumer electronics, but I'm still damn glad they are around. Their selection is limited, by they typical have the stuff you would need for repairs. In many rural areas its them or ordering online.

didnt mean to offend. i went to RS, because it was close for a common resistor, no luck, i just shook my head at what RS has become from what it use to be. we also have one or 2 "true" electronics parts stores, that arent much either. it is easier just to order, it gets here in a day or 2. but i am surprised they are still in business, did you find the post about RS? seems i am not alone on this thought. again, sorry to offend

Cornpanzer · 02-02-2009, 01:55 PM

I understand what you are saying with radio Shack, but in thier defense, is there really such a thing as a "common resistor" any longer? Does anyone sell enough resistors to keep a national chain of stores open. We are disposable consumers...hardly anyone fixes stuff anymore and those of us who do are a dying breed.

T77911S · 02-02-2009, 05:20 PM

when i was a kid i remember the vacuum tube testers and stuff at RS. not that i am young, i worked on a vacuum tube radar system in the military and still tinker with VT guitar amps. but back then, im sure RS WAS THE PLACE to go. i think i was looking for just a 4.7k resistor to bias a friends amp, they did not have it.