Visual Inspection; Semiconductor Checks - Tektronix 221 Instruction Manual

Preventive Maintenance—221 Service

Visual Inspection

The 221 should be inspected occasionally for such
defects as broken connections, improperly seated transis­
tors, damaged circuit boards, and heat-damaged parts. The
corrective procedure for most visible defects is apparant;
however, particular care must be taken if heat-damaged
components are found. Overheating usually indicates other
trouble in the instrument; therefore, correcting the cause of
the overheating is important to prevent recurrance of the
damage.

Semiconductor Checks

Periodically checking the semiconductors in the 221 is
not recommended. The best check of semiconductor
3-2
Fig. 3-2. Lead configurations of the semiconductors used in the 221 Oscilloscope.
REV. APR 1974
performance is actual operation in the instrument. If
checking the performance of a semiconductor out of the
instrument is desired, a dynamic checker, such as the
Tektronix Type 577 Curve Tracer system, is recommended.
Lead configurations of the semiconductors used in the 221
are shown in Fig. 3-2.
An extracting tool should be used to remove the
eight-pin fla t integrated circuit to prevent damage to the
pins. If an extracting tool is not vailable when removing one
of these integrated circuits, pull slowly and evenly on both
ends of the device. Avoid having one end of the integrated
circuit disengage from the socket before the other, as the
pins may be damaged. When replacing semiconductors, key
the semiconductor index w ith that of the socket. Failure to
do so w ill result in damaged components.
© l