Adjustments And Troubleshooting; Adjustments; 7-2-L Environmental Conditions; 7-L - Keithley 776 Instruction Manual

Adjustments and
Troubleshooting
7-1. Introduction
This section contains information necessary to adjust
and troubleshoot the Model 776 and the 2.1G option.
WARNING
The procedures described in this sec-
tion are for use only by qualified
service personnel. Do not perform
these procedures unless qualified to
do so. Many of the steps covered in
this section may expose the individ-
ual to potentially lethal voltages that
could result in personal injury or
death if normal safety precautions
are not observed.
7-2. Adjustments
7-2-l. Environmental Conditions
Adjustments should be performed under laboratory con-
ditions having an ambient temperature of25'15 "C. and
a relative humidity of less than 70%. If the instrument
has been subjected to conditions outside these ranges.
allow at least one additional hour for the instrument to
stabilize before beginning the adjustment procedure.
7-2-2. Warm-Up Period
Most equipment is subject to at least a small amount of
drift when it is first turned on. To ensure long-term
calibration accuracy. turn on the power to the Model
776. and allow it to warm-up for at least 30 minutes
before beginning the adjustment procedure.
7-23. Recommended Test Equipment
Recommended test equipment for calibration is listed in
Table 5-2. Test instruments other than those listed may
be used only if their specifications equal or exceed the
required cha~racteristics.
7-24. Adjustment Procedures
All adjustments are performed with the POWER switch
ON. The top cover should be removed to allow access
to test points, and adjustments. Between adjustments.
always leave top cover on the unit to keep intcmal
temperature.
WARNING
Take special care to prevent contact
with live circuits. or power line arca
which could cause electrical shock
resulting in serious injury. or death.
Use an isolated tool when making
adjustments. Use plastic or nylon
screwdriver when adjusting the time
base trimmer: other materials could
cause confusion in this adjustment.
Refer to Figure 7-1. throughout the following adjust-
ment procedures. for determining adjustment points.
Follon, the procedure in the sequence indicated because
some of the adjustments are intcrrelatcd. and dcpcndent
on the proceeding steps.
7-l