Keithley 2002 Repair Manual page 86

Bit patterns
Test 404.3 — Absolute value X1 gain, zero DAC
Type
Fault message
Description
Drawing reference
Components
Bit patterns
—U811—
00001101
—U224—
00010111
—U400— —U432—
01011100 01001100
*Bits associated with register IC terminals as follows:
Q Q Q Q
87654321 87654321
IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.
Pass/Fail
Absolute value gain = 1
DAC U433 and op amp pair U430 are set up to generate .001 VDC at PRECOMP+. This signal
has the same path to FWR as test 404.1. In this test, AMP IN positive, NETOUT from U417, the
ZERO CROSSING amp, and the COMP- signal that is tied to comparator U408 select the non-
inverting path for the AMP IN signal. Also, the AMP IN path is through R452, Q412, Q411,
U417, R453, U410, Q404, and U419 to pin 12 of multiplexer U414. The output of U414 is tied
to the A/D through buffer U403, ACV/A input to U222, and the A/D buffer in X1 gain configu-
ration.
Analog Board; 2002-100
U403, U414, U417, U419, U428, U430, U433, and associated components.
—U811—
00001101
—U224—
00010111
—U400— —U432—
01011100 10000000
*Bits associated with register IC terminals as follows:
Q Q Q Q
87654321 87654321
IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.
Bit pattern*
—U810—
00000011
—U206—
01110000
—U203—
10001110
—U411—
11111011
Q Q Q Q
87654321 87654321
Bit pattern*
—U810—
00000011
—U206—
01110000
—U203—
10001110
—U411—
11111011
Q Q Q Q
87654321 87654321
Troubleshooting
Register
—U809— AD_STB
11100111
—U207— MUX_STB
11001111
—U221— R1_STB
11101001
—U406— R2_STB
01001100
Register
—U809— AD_STB
11100111
—U207— MUX_STB
11001111
—U221— R1_STB
11101001
—U406— R2_STB
01001101
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