Sony KV-27S42 capacitors and ripple current

[MarkFromCA]

Hi,

Had a general question regarding replacement of electrolytic capacitors in a Sony KV-27S42 tv. I can find the important specs in the service manual but nothing about ripple current ratings. What's usually best to look for here? This is a measure of capacitor longevity, correct?

Thanks!

[vol.2]

Originally Posted by MarkFromCA

Hi,

Had a general question regarding replacement of electrolytic capacitors in a Sony KV-27S42 tv. I can find the important specs in the service manual but nothing about ripple current ratings. What's usually best to look for here? This is a measure of capacitor longevity, correct?

Thanks!

No. You misunderstand.

Ripple current is the amount of continuous ripple that the capacitor is capable of handling over it's useful service life.

This is generally only important for capacitors that are used to smooth out AC in a power supply circuit, and not a huge concern for capacitors that only see little bits of AC swing, like in signaling and smoothing out little bits of mV level ripple in a DC to DC circuit.

What you want to pay attention to is the voltage rating and the capacitance. If you are replacing a cap in the power supply, then you can up the voltage rating a bit to make sure it's good. For a normal USA ~120V supply filter cap, you might go up to 200V or 250V just to be safe and make sure it lasts, but be aware that it will be more expensive.

In general, don't get caps of different capacitance unless you have a full understanding of what they do in their spot in the circuit.

[MarkFromCA]

Thanks! I know at least enough to not deviate from stated capacitance and minimum voltage. It's nice to know that ripple current won't make much difference for most applications. The power board is actually where I may be replacing capacitors but I'd like to test them out of circuit first.

[vol.2]

Originally Posted by MarkFromCA

It's nice to know that ripple current won't make much difference for most applications.

To be more accurate:

Ripple current rating does matter, but most modern electrolytic caps will meet or exceed the necessary ripple current rating for the majority of signaling and DC filtering applications for which a circuit designer would choose an electrolytic cap.

Designers will generally not use electrolytics for lower capacitance applications that require big ripple handling, they will use film caps.

However, film caps start getting really expensive when you crank up the capacitance, so you start having to use electrolytics for large values, and so it's only when you're dealing with spots that have big AC noise on them that you have to start gawking at ripple current figures on datasheets.