Vectronics VEC-1220K - Manual (Page 7)

VEC-1220K/1230K/1240K/1280K Owner's Manual
5
monolithic and disc-ceramic capacitors are marked with a three-number code.
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. Electrolytics 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 slightly
shorter than the positive lead.
Diodes:
Diodes are also polarized devices that must be installed correctly. Always look
for the banded or cathode end when installing, and follow instructions carefully.
Cathode
Diode LED
(shorter Lead)
Transistors:
If transistors are installed incorrectly, damage may result when power is applied.
Transistors in metal cases have a small tab near the emitter lead to identify
correct positioning. Semiconductors housed in small plastic cases (TO-92) have
an easily-identified flat side to identify mounting orientation. Many specialized
diodes and low-current voltage regulators also use this type packaging. Larger
plastic transistors and voltage regulators use a case backed with a prominent
metal tab to dissipate heat (T-220). Here orientation is indicated by the
positioning of the cooling tab.
Emitter
Flat Side
Metal Tab
Metal Can Device Plastic Device Tab-cooled Device
Integrated Circuits:
Proper IC positioning is indicated by a dot or square marking located on one end
of the device. A corresponding mark will be silk-screened on the PC board and
printed on the kit's parts-placement diagram. To identify specific IC pin
numbers for testing purposes, see the diagram below. Pin numbers always start
at the keyed end of the case and progress counter-clockwise around the device,
as shown: