Keithley 237 Service Manual

SECTION 3
Maintenance
37
SPECIAL
HANDLING OF
STATIC
SENSITIVE
DEVICES
CMOS
devices operate at very
high impedance levels
for
bw
power consumption. As
a
result,
any static that
builds
up on your person or ciothing may be
sufficient to
destroy these
devices, if they are not handled
properly.
Use
the following precautions to
avoid damaging them.
1. ICs should be transported
and handled only
in con
tainers
specially designed to prevent
static buildup.
Typically, these parts wffl be
received in antistatic
containers
of plastic or foam. Keep these devices in
their original
containers until ready for installation.
2.
Remove
the devices from their protective containers
only at
a
properly grounded
work
station.
Also,
ground yourself with a suitable wrist
strap.
3,
Handle the devices only by
the
body; do
not touch
the
pins.
4, Any printed circuit board
into which the device is to
be
inserted must also
be
grounded to the bench
or
ta
ble,
5, Use
only antistatic type
solder sucker.
6.
Use only grounded tip
solder irons.
7, Once the device is installed in the PC board, it is
nor
mally adequately protected, and normal
handling
can resume.
38
TROUBLESHOOTING
The troubleshooting information contained in this sec-
tion is intended
for use
by
qualified personnel having
a
basic understanding
of analog and digital circuitry. The
individual
should
also
be
experienced at using
typical
test
equipment
as
well
as
ordinary
troubleshooting pro-
cedures. The information presented
here has been writ
ten to assist
in isolating
a
defective circuit or circuit sec-
tion. Isolation of
a
specific component is
left
to
the techni
cian. Note that
schematic diagrams and component
loca
tion drawings, which are an essential aid to
troubleshoot
ing. are
included
in Section
5.
38.1 Recommended
Test Equipment
Success
in
troubleshooting complex
equipment like the
Model 236/237
depends not only on
the skill of the tech
nician, but relies
on the use of accurate,
reliable
test
equipment.
Table
3-2
lists the equipment
recommended
for troubleshooting
the Model 236/237.
Other
equip
ment,
such
as
logic analyzers
and capacitance checkers,
could also be helpftil.
Table 3-2.
Recommended
Troubleshooting
Equipment
Equipment
Use
Five
function DMM with
Power supply and
dc
0.1%
basic
dcV
accuracy,
voltage checks; analog
1OM
input impedance
signal tracing continuity,
logic levels.
Dual-trace,
triggered
Digital and analog
sweep
oscilloscope, dc to
waveform
checks.
50MHz
Digital frequency counter
Checking
clock
frequen
cies.
3.8.2
Diagnostics
The Model 236/237
has some internal diagnostic
capa
biities to
aid in troubleshooting.
Power-up
and MEMORY TEST
On
power-up or when the Memory Test
is
run, the Model
236/237
performs a series
of
tests
on its
memory ele
ments.
If
a
failure occurs, one or
more
front
panel
mes
sages
are
displayed.
Perform
the following steps to
perform the Memory
Test:
1. Enable
MENU and use
the rotary knob to
display
“MEMORY TEST“.
2.
Press
ENTER. If the test passes,
the display
will
blank for a
couple of seconds
and display the
next
menu item.
Otherwise,
a
failure will cause one or
more front
panel
messages to be
displayed.
Note: The Memory
Test can
also
be
run
by
sending
J1x over
the bus.
The
front panel messages
associated
with memory ele
ment failures
are explained as
follows.
3=11

Keithley 237 Specifications

General

Output Power	200 W
Voltage Resolution	1 μV
Current Resolution	10 fA
Type	Source Measure Unit
Interface	GPIB, RS-232
Accuracy	0.02%
Compliance Voltage	±1100V