Tektronix 442, Instruction Manual

Page: 76 / 170

Maintenance—442 Service
CAPACITOR MARKINGS. The capacitance values of
common disc capacitors and electrolytics are marked on
the component body. Some ceramic capacitors used in
the 442 are color coded in picofarads, using a modified
El A code (see Figure 5-3).
The dipped tantalum capacitors used in the 442 are
color coded in microfarads (see Figure 5-3). The color dot
indicatesthe positive lead and voltage rating. Be carefulto
observe the polarity and voltage rating, as capacitors are
easily destroyed by reverse or over voltage.
DIODE COLOR CODE. The cathode end of each
glass-encased diode is indicated by a stripe, a series of
stripes, or a dot. For most silicon or germanium diodes
with a series of stripes, the color code identifies the three
significant digits of the Tektronix Part Number using the
resistor color-code system (e.g., a diode color-coded pink
or blue-, brown - gray - green indicates Tektronix Part
Number 152-0185-00). The cathode and anode ends of
metal-encased diodes can be identified by the diode
symbol marked on the body.
POWER CORD CONDUCTOR IDENTIFICATION.
Refer to Section 2, Operating Instructions, for color code
information pertaining to power cords available for the
442.
SEMICONDUCTOR LEAD IDENTIFICATION. Refer
to Figure 5-4 for lead identification for semiconductors
used in the 442.
MULTI-PIN CONNECTOR HOLDER ORIEN­
TATION. Small multi-pin connector holders are indexed
with two triangles to identify pin 1. One triangle is located
on the holder, and the matching one is located on the
etched circuit board near pin 1 of the mating connector
(see Figure 5-5).
Some large multi-pin connector holders are indexed
with the trade name at the pin 1 end and pin 1 may or may
not be marked on the circuit board. In some applications,
the jack or plug number may be marked on the board near
the pin 1 end.
Troubleshooting Equipment
Refer to Table 5-3 at the end of this section for a list of
suggested equipment to use for troubleshooting the 442.
(0 9 9 5 - 1 1 ) 2 3 7 4 - 2 1 A
Figure 5-5. Multi-pin connector holder indexing.
Troubleshooting Techniques
This troubleshooting procedure is arranged in an order
which checks the simple trouble possibilities before
proceeding with extensive troubleshooting. The first few
checks ensure proper connection, operation, and calibra­
tion. If the trouble is not located by these checks, the
remaining steps will aid in locating the defective compo­
nent. When the defective component is located, it should
be replaced following the replacement procedure given
under Corrective Maintenance.
1. CHECK CONTROL SETTINGS. Incorrect control
settings can give a false indication of an instrument
malfunction. If there is any question about the correct
function or operation of any control, refer to the Operating
Instructions section of this manual or the 442 Operators
manual.
2. CHECK ASSOCIATED EQUIPMENT AND CON­
NECTIONS. Before proceeding with troubleshooting,
check that the equipment used with this instrument is
operating correctly. Check that the signal is properly
connected and that the interconnecting cables are not
defective. Also, check the power source (including the
power cord and plug).
3. CHECK INSTRUMENT CALIBRATION. Check the
calibration of this instrument, or the affected circuit if the
trouble exists in one circuit. The apparent trouble may
only be the result of misadjustment and may be corrected
by proper adjustment. Complete adjustment instructions
are given in the Calibration Procedure section of this
manual.
REV A MAY 1980
5-7