No, but this is typical of comments people find online.

NOTE: DIY electronic equipment repair attempts often fail to resolve faults and significantly increase the risk of damage, introduction of additional faults and electrocution. Stay safe and if in doubt, take equipment to a professional.

Dunning-Kruger

With any technical concept, the details are nuanced and one cannot expect to know much after just a few hours of reading. The Dunning-Kruger effect is where people significantly overrate their understanding of topics they’ve learned little about, usually from untrustworthy sources.

We see this play out everywhere, like this Hollywood actor who thinks he knows better than the world’s greatest mathematicians and physicists. Public forums are a haven for uninformed chit-chat about many things including electronics and many come unstuck by relying on them as a source of information.

Again, if in doubt, seek a professional, and note that professionals don’t hang out in public forums!

Example

Capacitors are one of many poorly understood topics in electronics, with ‘recapping’ being right up there. A reader’s comment on an article I wrote about the wonderful Kenwood KD-500 turntable prompted me to write this FAQ. Let’s examine this and then break it down a little:

A simple fix can be changing any electrolytic caps.. Always good to remove then and check there [sic] capacitance. 10% below should be changed.

Mark

Breakdown

Mark’s statement is incorrect. Not only will not help the original commenter fix his turntable, it will most likely lead to the owner damaging and devaluing his turntable, and it will still have speed issues after all that. I understand the causes of the speed issues with these turntables and they are not capacitor-related.

I replied as follows:

Thanks for your comment, Mark. I appreciate trying to assist others, but given that your comment highlights general misinformation regarding technical electronics repair and only encourages capacitor replacement rather than finding and fixing the issues, it’s helpful if I explain why.

Capacitors are much maligned and poorly understood. Capacitors should be checked, but rarely cause speed issues with these decks. New caps are typically specified to be within +/- 20% of rated capacitance, like these excellent Panasonic parts: https://industrial.panasonic.com/cdbs/www-data/pdf/RDF0000/ABA0000C1209.pdf.

A reading within +/- 20% is within new part specs and measurement error. Replacing capacitors that measure within 10% of spec is not only a waste of time and money, but it will not fix anything unless those parts also have a measurably very high ESR.

Most end-users also don’t have the test equipment needed to make these measurements accurately, nor the experience to interpret the results and therefore should not remove or change parts they cannot properly measure and assess.

Liquid Mike

Did You Know?

Did you know that brand-new capacitors typically measure low for C and high for ESR? There’s nothing wrong with them, they need to reform, the process that happens when they are first charged. According to the commenter’s theory, even brand-new capacitors that have sat for a while should be thrown away. This is, of course, incorrect.

Capacitors can fail and must be replaced when they do. They can also be replaced to significantly improve performance, depending on their role in a circuit. However, a 10% variance from rated spec does not constitute failure and may be within the measurement error of the typically ordinary test gear most owners will have access to.

TLDR

All too often, DIYers and unskilled technicians bin perfectly good parts and replace them with inferior parts, trying to solve problems that are not even caused by bad capacitors. ESR is a more important parameter than C in terms of capacitor health. Proper lab-grade test and measurement equipment is needed to properly test capacitor parameters, equipment most people do not own.

Replacing parts can cause circuit board damage and introduce new faults. This is especially for those working with cheap soldering and re-work tools, ie people who probably shouldn’t be doing the work. Again, glancing through the Hall of Shame provides ample examples of this flawed approach.