DIYbanter - View Single Post - Why should someone replace ALL the capacitors on old Tube equipment?

Ralph Mowery

In article ,
says...

In article t,
Ralph Mowery wrote:

Capacitors such as .047 have been around a long time. I don't know why
it is such an odd value as I doubt the extra .003 would be noticable in
the circuits most of them are used in. As the tollorance on most of the
electrolytics are very broad I don't understand the odd values either.

If you look at the standard values used for resistors and capacitors
and inductors, you can see that they tend to be spaced in a way which
creates something approximating a geometric ratio - that is, each
value in the series is 1-point-something times the previous value.
The higher-precision value "kit" has a total of 24 values over each
decade. The common lower-precision value kit has six values (every
fourth, from the 24-value higher-precision range).

The relationships aren't exact - 0.047 would be 0.046415... and
some of the other "traditional" values are even further off of the
geometric curve. But, that's the basics of it.

I imagine that when picking the values which would go in the
lower-precision set, it was easier to just choose the same nominal
values as were used in the higher-precision set, and specify a lower
tolerance (e.g. +/- 10% for a cheap film cap, or +100/-20 for a
'lytic).

I had forgotten that the resistors were valued at some math function.
Did not know the capacitors and inductors were the same, but seems
reasonable.
As pointed out, almost nothing in electronic components is exact for
normal circuits.