Vectronics VEC-1500K - Manual (Page 38)

33
Multilayer caps are similar to a surface-mount "chip" capacitors, except that
leads are spot-welded onto each end of the capacitor body. Multilayers have
superior operating characteristics, but the lead welds may fail if the device is
over-stressed. For this reason, never use force to seat a multilayer cap into the
PC board. If the spacing isn't right, pre-form the leads to the correct spacing
before installation!
Incorrect
Ooops! Correct
For ceramic disc and multilayer capacitors, the transition from pF (pico-Farads)
to uF (micro-Farads) occurs at 1000 pF (or .001 uF)*. The first two digits
indicate a numerical value, while the last digit indicates a multiplier (same as
resistors).
Electrolytic capacitors are always marked in uF. Electrolytic are polarized
devices and must be oriented correctly during installation. If you become
confused by markings on the case, remember the uncut negative lead is always
slightly shorter than the positive lead.
Chokes and Inductors
Chokes block the flow of AC current while permitting the passage of DC.
Molded chokes commonly used today are color-coded in much the same way as
resistors (see below). While some chokes are specified in nano-Henries (nH) or
milli-Henries (mH), most used in communications work are specified in micro-
Henries (uH). The choke's third color band specifies its range. For example, a
red, red, silver choke is .22 uH, a red, red, gold choke is 2.2 uH, a red, red, black
code is 22 uH, and red, red, brown means 220 uH. The fourth color band
indicates tolerance10% for silver and 5% for gold.
1st Digit
2nd Digit
Multiplier
Tolerence
Black = 0 (tens uH)
Brown = 1 (hundreds uH)
Red = 2 (mH)
Orange = 3
Yellow = 4
Green = 5 Blue = 6
Violet = 7
Gray = 8
White = 9
Silver = .10 uH or 10%
Gold = 1.0 uH or 5%
Molded Choke Color Code
(gold or silver)