I have an old audio amplifier (JVC A-GX2B) that sometimes produces crackling noises on one of the outputs. So, I opened it and discovered that its two largest capacitors seem to be leaking :

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Can I replace it with any capacitor with the same characteristics (4700uF 50V), or should I instead take specific capacitors for audio? If yes, which ones ?

In addition, do I have interest to replace all the capacitors of this amp (not only the 2 largest)?

  • \$\begingroup\$ I'd be using the same technology of capacitor, Aluminum Electrolytics. Make sure you put the new ones in the same way round. Mark the polarity on the board before you remove them if there is not an indication there already. \$\endgroup\$
    – Trevor_G
    Jan 20, 2018 at 16:22
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    \$\begingroup\$ The fluid that leaks out of an Aluminum Electrolytic capacitor is very aggressive. You can see your other components have been damaged as well. I suggest you clean up very well and contemplate replacing some of those too. Also check your copper traces for damage. Yes, I suggest you replace both capacitors. I have not seen stats but I found Aluminum Electrolytic capacitors are often the first to fail in designs. \$\endgroup\$
    – Oldfart
    Jan 20, 2018 at 16:25
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    \$\begingroup\$ That looks more like glue than it does electrolyte. \$\endgroup\$
    – JRE
    Jan 20, 2018 at 18:04
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    \$\begingroup\$ In other words, the problem lies elsewhere. \$\endgroup\$
    – JRE
    Jan 20, 2018 at 18:07
  • \$\begingroup\$ Those two big capacitors are in the powersupply. If they were bad, you'd have problems on both channels, not just one. \$\endgroup\$
    – JRE
    Jan 20, 2018 at 18:17

2 Answers 2

  • 1: wear safety gloves when handling toxic leaky capacitors, remove and clean safely with isoprop. and mark note polarity (-)
  • 2 : measure dia and Lead pitch DxL [mm] then sort parts by this
  • 3: audio or better low ESR, highest ripple current caps. < 50mOhm, > 3Aripple
  • 4: better caps run cooler with lower ESR and rated for higher temp. but may not fit.
  • 5: Japanese Caps have better reliability
    • I suggest 1st choice Panasonic at Digikey .. cost of shipping may be more than cost of caps.

as suggested: Cap voltage must be same or more
- also capacitance tolerance doesn't matter, and may be larger value.
- all large e-caps may be replaced at same time.

  • 1
    \$\begingroup\$ One more point: Voltage rating should be >= current caps. \$\endgroup\$
    – vofa
    Jan 20, 2018 at 17:26
  • \$\begingroup\$ +1 re: cost of shipping may be more than cost of caps. Got burned with that once... paid like $26 for a $1 part to enter Canada.... \$\endgroup\$
    – Trevor_G
    Jan 21, 2018 at 2:52

I'm not going to answer the question you've posed - Tony Stewart has done a good job of that.

I'm going to address your assumption that those capacitors have leaked.

Capacitors and other parts are often glued into place in audio circuits. If they could move, then they could cause noise. Sometimes, in an effect called "microphony" parts will pick up sounds or vibrations and inject them into your audio. If the parts are glued in place, then they are far less likely to cause problems.

Large parts (like your capacitors) can also break off from their own weight if the board is accelerated violently (say, dropped on the floor.)

Your capacitors appear to be glued down. The glue is often a brownish color as in your pictures. Also note that it only extends a couple of millimeters around the part. If it were leakage, it wouldn't be as evenly distributed.

The electrolyte is corrosive. If the stuff you see were electrolyte, the wires on the parts that have brown stuff on them would be greenish (copper turns green when it corrodes.)

Finally, those capacitors appear to be in the powersupply. If they were the cause of the noise, it would cause noise on both channels at the same time.

So, I think your problems lies elsewhere.

I would check the volume control and the connectors for the noisy channel. Wiggle the volume control and see if it causes noise. Wiggle all the connectors and see if they make noise.

After that, flip the board over and look for solder joints that have gone bad.

Often times on old equipment, you will find a part with a leg that has a "ring" around the pin where it comes out of the solder on the back of the board. Heat and vibration weaken the solder, and the pin breaks loose. It isn't soldered any more, but it still conducts, because the pin is still mechanically in contact with the solder. Vibration causes it to lose contact, and you get noise.

  • \$\begingroup\$ Thanks for your answer! Indeed, my problem may not be the capacitor.... I will look elsewhere thanks to your advice! \$\endgroup\$
    – Alain
    Jan 21, 2018 at 19:59
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    \$\begingroup\$ I cleaned all the electronic boards whith a "cleaning contact" product and the result was amazing, no more crackling noises, even after 2 months. Thanks again ! \$\endgroup\$
    – Alain
    Apr 3, 2018 at 16:45
  • \$\begingroup\$ I might add that sometimes bad solder joints cannot be detected visually. I recently touched up the three pins of one transistor that looked OK. I confirmed that transistor was causing the crackling noise the internal amplifier of my old subwoofer makes when warmed up. I touched up the solder joints of the pins of this transistor and the noise disappeared completely. A more detail in the Answer I posted in my own thread: electronics.stackexchange.com/questions/289929/… \$\endgroup\$
    – zeron
    Jul 28, 2018 at 20:31

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