anyone replace capacitors on a component?

[Deleted member 234478]

im going to recap my subs plate amp.

I have a quiet hum and usually I cant hear it but at the times I can is annoying. its not ground loop. I tested circuitry ground with a specific tested. ground is good. hum is even when no rca is connected in from AVR. different power outlet. all the same. I got the sub and its in mint condition, I think its quite an old sub.

looking for an online store that INTL ship high quality caps and where are good caps made?

japan, eu, usa?

 

[Harlow]

I got the sub and its in mint condition. I think its quite an old sub.

Is this merely the sub's outward appearance? The case could be pristine but the electronics inside might be junk.

looking for an online store that INTL ship high quality caps and where are good caps made?

Before replacing any electrolytic capacitors which may have dried out, I suggest checking them all with an ESR meter. This will show if the marked capacitance is the same as the measured capacitance and also tell you the equivalent series resistance.
https://www.yamanelectronics.com/test-capacitor-without-desoldering/

When possible, I recommend isolating one leg of each capacitor before making measurements, to avoid any other components affecting the reading. This might be too difficult if it means unsoldering both legs of a PCB mounted capacitor with the risk of damage.

When you've tested all the electrolytics, you'll know which components need replacing.

Most reputable suppliers should stock good quality capacitors, regardless of country. If you check ATX PSU "tier lists" you may find recommendations for good quaility capacitors, often described as Japanese, despite their being made in China.

If the capacitors are part of a PSU, look for low ESR components with high ripple current rating. When used as coupling capacitors in audio stages, consider "audio grade" components. You might even need "non-polarized" audio capacitors. Check the information printed on the outside of each capacitor and do a search on the internet. Even better, find a repair manual for the sub.

As a rough guide, try to match the physical size and shape when replacing a capacitor, in addition to its value in microFarads and working voltage. Capacitors with higher ripple current ratings tend to be larger than capacitors with the same uF/V rating, but with lower ripple current.

If you follow these rules and try to match any bad components as closely as possible, you might effect a cure and reduce hum. Then again, the design might not be perfect and you'll never remove all hum. Subs may be subject to 50/60Hz mains hum breakthrough near the middle of the frequency range of the woofer.

 

[nomdeplume]

Before replacing any electrolytic capacitors which may have dried out, I suggest checking them all with an ESR meter.

With due respect the established practice in audio is to replace them all and all at the same time. Consider this a practical addendum to your solid response.

A fair amount of thought on design topology is required if any changes in type or rating of capacitor are necessary. You should also place susceptibility towards upgrading into this same category. It really pays off to understand the design in order to determine if time and effort invested will remove flaws or produce an untenably long period before sound returns to a static accurate portrayal.

 

[Wirko]

With due respect the established practice in audio is to replace them all and all at the same time. Consider this a practical addendum to your solid response.

But why? You can't assume that all electrolytic capacitors are of the same quality and exposed to the same temperature (including self-heating from ripple), which is a major factor in aging and degradation. They are components with a *relatively* high failure rate, which still doesn't mean high. If I took all caps from all my audio, measurement, computer equipment (in large part, 3 - 5 decades old), most would still be almost like new.

I suggest checking them all with an ESR meter.

That's a great advice - if you have one. However, all the failed caps I've ever found had their capacitance greatly reduced, so much that ESR measurement was not even necessary. It seems that the failure mode where a cap would retain its capacitance, but have its ESR significantly increased, is impossible (or almost).

 

[Shrek]

Almost, I had a capacitor in a 40-year-old smoke detector still report good capacitance; replacing the capacitor fixed the unit.

That said, I agree.


My Fluke 110 meter reported

• 5.18μF

for a 4.7μF capacitor, while my Peak ESR70 meter reported

• 1.58μF and an ESR of 12.6Ω

A new capacitor had an ESR of just over 1Ω

 

[nomdeplume]

But why?

Ask the OP what highly accurate measurement tool they applied to determine the need for repair as surely as they will reapply it to determine worth of labors undertaken.

 

[Sabbath]

My Mum's Sony soundbar stopped working, so I got some capacitors off Amazon after googling common problems, swapped the capacitor and it worked. I was lucky as I could see the blown one.

 

[Shrek]

For power supplies I tend to stick with low ESR capacitors and 105°C rating from

• Rubycon
• United Chemi-Con (or Nippon Chemi-Con)
• Nichicon
• Sanyo/Suncon
• Panasonic

but even then, they have different series. I try to keep the physical size the same, especially the diameter.