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ChrisCwmbran

Experienced Member
Joined
Oct 11, 2011
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483
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Cwmbran, Wales, United Kingdom
During my time on the forum I have learnt that some capacitors such as the RIFA X2 capacitors are common to lots and lots of machines.

Clearly the range of capacitors on the market is huge but is there a set of sizes and voltages that I'm going to come across time and time again? i.e. Electrolitic sizes, and maybe tantalum sizes?

Is there anything other than capacitors that will fall into the same category?

At the moment ordering bits and pieces is costing as much in shipping as the actual parts cost.

Any advice would be greatfully received!

Thanks!
 
Almost all non-active components such as Resistors, Capacitors and to some extent Inductors exist in standard sizes and values. So the common resistors ranges are described by their power disapation, so 1/8 Watt, 1/4 Watt, 1/2 Watt which governs the size of the resistor. There is also a standard range of values called "preferred values". The most common ones are the E12 Series which has 12 values per decade. So between 1 ohm and 10 ohms will be:-

"1.0, 1.2, 1.5, 1.8, 2.2, 2.7, 3.3, 3.9, 4.7, 5.6, 6.8, 8.2"

The series starts again at 10 ohms, so we get 10,12,15,18,22,27,33,39,47,56,68 and 82. The starting again at 100....

http://www.logwell.com/tech/components/resistor_values.html
http://www.st-andrews.ac.uk/~jcgl/Scots_Guide/info/comp/passive/resistor/e12/e12.html

Capacitors also follow a similar set of values, as do inductors. Hope this helps
 
The rule of thumb is that no matter how large your inventory, out of the [any number] parts you need you will be missing at least one crucial one and have to order it.

But seriously, in many cases the value of a capacitor or resistor is not really critical so you don't really need *every* value; also, within reason and within size constraints you can usually use an electrolytic or tantalum capacitor with a higher voltage than the original. Electrolytics are generally higher capacity and voltage values than tantalums, but where they overlap you can usually use one instead of the other.

Resistors don't fail often and when they do it's probably because something else like a transistor failed. In any case you are unlikely to need anything other than 1/4 W; anything larger you'd probably have to order anyway. Also note that you can combine resistors in series and/or parallel to create different resistance values.

An assortment of tantalum caps of every third value or so at 16V might be a good way to start.
 
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