Tektronix 442, Instruction Manual

Page: 81 / 170

Maintenance— 442 Service
SYMPTOM 2— Trace is present on the crt screen, but
the trace is too short.
a. Check collectors of Q2334 and Q2344 for a ramp
signal of approximately 40 volts amplitude (amplitude will
vary with setting of Horizontal POSITION control).
b. If there is no ramp signal at Q2334 or Q2344
collectors, check for a 12 volt ramp at the junction of
R2243-R2311-C2246-R2245 (see Sweep and Horizontal
Amplifier schematic diagram).
c. If a 12 volt ramp is present, check Q2332, Q2334, or
Q2344 (see Horizontal Output schematic) and Q2314,
Q2326 (see Sweep and Horizontal Amplifier schematic
diagram).
C O R R E C T IV E M A IN T E N A N C E
Introduction
Corrective maintenance consists of component
replacement and instrument repair. Special techniques
required to replace components in this instrument are
given here.
Maintenance Precautions
To reduce the possibility of personal injury or instru­
ment damage, observe the following precautions.
1. Disconnect the 442 from the power source before
removing or installing components.
2. Use care not to interconnect instrument grounds,
which may be at different potentials (cross grounding).
3. Do not use excessive heat when soldering. This can
damage circuit boards and semiconductors.
Static-Sensitive Components
Static discharge can damage any semiconductor
component in this instrument.
This instrument contains electrical components that
are susceptible to damage from static discharge. See
Relative Susceptibility table for various classes of
semiconductors. Static voltages of 1 kV to 30 kV are
common in unprotected environments.
Observe the following precautions to avoid damage.
1. Minimize handling of static-sensitive components.
2. Transport and store static-sensitive components or
assemblies in their original containers, on a metal rail, or
on conductive foam. Label any package that contains
static-sensitive assemblies or components.
3. Discharge the static voltage from your body by
wearing a wrist strap while handling these components.
Servicing statiq-sensitive assemblies or components
should be performed only at a static-free work station by
qualified service personnel.
4. Nothing capable of generating or holding a static
charge should be allowed on the work station surface.
5. Keep the component leads shorted together
whenever possible.
6. Pick up components by the body, never by the leads.
7. Do not slide the components over any surface.
8. Avoid handling components in areas that have a
floor or work-surface covering capable of generating a
static charge.
9. Use a soldering iron that is connected to earth
ground.
10. Use only special antistatic suction type or wick
type desoldering tools.
5-12
REV A MAY 1980