Haven’t a clue about practical electronics, what a diode is for, what potentiometer does etc.
So my question (please forgive me) is:
Do all NAIM separates have capacitors in them that need periodic replacement?
In short, yes.
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Yes. One of the reasons for a service. A service inspects and replaces items that have degraded, bring the item back to its designed condition. I.e. as per new.
A diode is an electronic component with two terminals that allows the flow of electric current in one direction. Diodes have low resistance in one direction and high resistance in the other, and their operation depends on the direction of voltage applied to their terminals. This operation is called rectification, and it’s the basic function of diodes
A potentiometer is a type of variable resistor. These are designed to control electrical resistance, measured in Ohms (Ω). Multiple different variations are available, including trimmer and rotary potentiometers, but the functional principle remains the same.
Potentiometers work by picking up an input Voltage and transferring different amounts to a circuit. This amount is determined by the position of the wiper (sometimes also known as a slide) on a resistive track. A typical example of a potentiometer application is the volume control on radio and stereo systems. Some still have analogue rotary potentiometers installed and despite increasing digitalisation, potentiometers are often used in electronics like these. Potentiometers may also be referred to as pots or potmeters.
A capacitor is a device that stores electrical energy by accumulating electric charges on two closely spaced surfaces that are insulated from each other.
Naim equipment has capacitors and, these will need replacing every so often, hence the serving of Naim amps at scheduled frequencies.
DG…
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Pots = Potential dividers.
All home electronics have capacitors. Most will have one or more electrolytic capacitor (or many). These have a much shorter lifespan than ceramic capacitors and often the primary reason for home appliances like air conditioners, microwave ovens, televisions, computers, reaching a final failure point.
Knowing how to safely replace (recap) anything (or replace other common components that have a shorter lifespan like motors, solenoids, pots etc.) can save you a lot of money over the years. Though if we all did this, a lot of retailers would go bust I suspect. With a bit of training you’ll never be buying a new electric mixer again 
Of course with hifi, a manufacturer provided recap is highly recommended if offered. They have the known grading and test rig for implementing the correct and matched replacements.
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Pretty much, yes. The concern is mainly Electrolytic Capacitors.
These deteriorate with time, from the date of their manufacture. It doesn’t matter if they are powered or not.
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Great pun! 
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I find a petrol mixer is a lot more convenient and easier to service.
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And the little tantalum bead capacitors, of which there were many in both our NAC32.5 and NAC52.
Best regards, BF
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Thanks. The reason I asked is because I’m getting my 282 serviced for a faulty balance control. The firm involved (in Holland) then recommended I also get my NAPSC serviced.
I thought that capacitors were only present in power supplies so I queried their response re: caps in the 282.
After some back and forth at a similar level of numpty to this, they explained the case for the 282.
Musing on this, I thought about my nDac, so that’s why I asked this question. I guess that’s the next box for treatment.
Yes for the Classic range, really 15 years is the max before a recap sjould be done. The kicker though, is that when things need recapping, the sound goes off gradually and you might not notice immediately. But when they are recapped they are like new… including the somewhat rough burn in period which may make them somewhat less good than when you sent them off until run in where they sound better. Of course if you waited really a long time to recap, then even a non run in serviced box will sound better than before you sent it in.
Food for thought.
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Follow up numpty question,
does usage have affect time for replacement, say 2 hours daily vs 6?
Temperature does, yes. Even sitting on a shelf, they dry out eventually. Most manufacturers recommend using caps within 2 yeara from manufacture date to ensure the product they go in has a reasonable service life.
Like most things, they tend to fail on power on more than when constantly powered, but constantly powered may run warmer and shorten the life. In other words, it’s not clear cut and depends on a lot of environmental factors.
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The biggest influence on capacitor life is temperature. Life doubles for every 10degC decrease in temp.
In general, 15 years is a sensible period after which to inspect/replace.
BTW, this is not a numpty question at all! There is a formula for calculating capacitor life, but that’s beyond tne scope of a quick form response.
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In my own experience, those capacitors that have failed, are those used in standby cicuits, that is, those who are always on.
In a cd player and in an amp.
I’m sorry, I don’t entirely agree with that. I think Google has led you astray (as search engines often do these days I find).
The first paragraph here in Wikipedia on the Lifetime is pertinent. Note it refers to time, temperature and current. The latter two affected by in-use time.
I didn’t expect the Spanish Inquisition. 
NO-ONE expects the Spanish Inquisition !!!
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