No, it isn’t.

With all technical topics, people don’t know what they don’t know, and a little knowledge can be a dangerous thing. With that in mind, I’m going to provide some simple factual information. Before we proceed, note that DIY electronic equipment repair attempts significantly increase:

1. The risk of equipment damage
2. The introduction of faults
3. The risk of personal harm through electrocution

Each of these outcomes is a bad time, so stay safe, and if in doubt, take your equipment to a professional.

Dunning-Kruger

The Dunning-Kruger effect describes people overrating their knowledge and understanding of topics they know too little about to know how little they know. One cannot know much about anything, let alone complex technical topics, after just a few hours of reading, especially when those sources are others with little knowledge.

You’ll see the problem and the dangers here: People treating cancer with fruit juice, launching themselves in rockets to ‘prove’ the Earth is flat, building deep diving submersibles out of carbon fibre and titanium glued together… Yeah. Again, if in doubt, seek an experienced professional, and note that such individuals rarely participate in public forums.

Capacitors and ‘recapping’ are two such poorly understood topics in electronics. A reader’s comment on an article I wrote about the wonderful Kenwood KD-500 turntable prompted me to pass on a little expertise on this topic, because goodness knows, it’s needed. Let’s examine this:

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 generic, regurgitated, and made without reference to the unit in question. It is also mostly wrong. Mark has likely not seen or repaired a KD-500. Not only will this advice not help the original enquirer fix his turntable, but it will likely lead to him damaging it, and it will still have speed issues.

The best part of Mark’s advice was that capacitors can be removed and tested for capacitance. True, though they don’t need to be removed in most cases. He ignored ESR, however, which is more important, and the damage DIYers often cause in removing parts.

My reply was polite and informative:

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

Facts (Are Useful)

I’ve provided a few facts here to help readers, from the standpoint of a trusted professional and science educator with an honours degree in science, working commercially with electronics, FWTW. The internet is an echo chamber for misinformation and pseudo-experts, unfortunately, and few knowledgeable folks take the time to correct things for a range of different reasons. I’m pleased to be one of the few who do.

Are capacitors important? Sure. Were they the cause of the issues with this KD-500 or any other? Not in my experience. Should all capacitors measuring “10% below” be replaced? No. Did you know that brand-new capacitors typically test low for C and high for ESR? There’s nothing wrong with them; they need to reform, a 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 the rated spec does not constitute failure and is within the margin of measurement error of the test gear most owners will have access to.

Summary

All too often, people bin good parts and replace them with inferior parts, trying to solve problems not caused by those parts. There is so much nonsense advice offered about replacing every capacitor after a certain age, but I can assure readers that no truly informed specialist would ever recommend this.

Anyone doing so knows too little to be helpful but enough to be dangerous, and is probably selling parts. One self-described ‘technician’ sells kits on eBay, no surprises here. No self-respecting technician sells, uses or recommends kits.

ESR is a more important parameter than C in terms of capacitor health. Proper lab-grade test and measurement equipment is needed to effectively test capacitor parameters; cheap multimeters cannot do it, and most people do not own expensive test and measurement equipment.

Replacing parts often causes circuit board damage and introduces new faults when done by inexperienced folks with poor rework skills and tools. The best way to save and rejuventate equipment is to have an expert do it, someone with hopefully a decade or three of best practice behind them.