Keithley 2002 Repair Manual

Troubleshooting
2-90
2.11.23 /750 frequency compensation tests
Test 409.1 — Circuit setup for test 409.2
Type
Pass/Fail
Fault message
None
Description
In this series of tests, DAC A of U433 is used to exercise the frequency compensation capacitors
C460 and C463 of NET1 (R488) and R489 (/500). In this phase, DAC A is programmed with 1s
(no compensation), and the output at pin 2 is tied to C463. BUFF is applied to NET1 (R488)
through R493. The voltage at pin 4 is tied to AC buffer Q418 and U423 through U428 and Q422.
The signal AMP IN is tied to the circuit through U425, U426, to Q414. This phase sets up the
conditions for the next phase; there is no measurement in this phase.
Drawing reference Analog Board; 2002-100
Bit patterns
Test 409.2 — Signal stored for test 409.3
Type
Circuit Exercise
Fault message
None
Description
The SELFTEST control line turns ON Q425 and forces the voltage on NET1 (R488) to ground.
The response of R488 pin 4 is stored in C439. This test uses the same path as test 408.1 except
as follows: when the SELFTEST control line forces the divider voltage to zero, it also generates
a one-shot pulse 5µs after SELFTEST goes low. This pulse turns Q414 on and stores the voltage
on C439. The 5µs delay that controls U425 and Q414 is generated by U402. No measurement
is made during this phase.
Drawing reference
Analog Board; 2002-100
Bit pattern* Register
—U400—
01111101
—U811—
00001101
—U224—
00010111
—U432—
11111111
—U810—
00000011
—U206—
01110000
—U203—
10001110
—U411—
00111010
—U809—
11100111
—U207—
11001111
—U221—
11101001
—U406—
01101110
AD_STB
MUX_STB
R1_STB
R2_STB
*Bits associated with register IC terminals as follows:
QQQQQQQQ
87654321 87654321 87654321 87654321
IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.

Keithley 2002 Specifications

General

Brand	Keithley
Model	2002
Category	Multimeter
Language	English