Keithley 2002 Repair Manual page 108

Bit patterns
Test 411.2 — Filter; variable gain amplifier
Type
Fault message
Description
Drawing reference
Components
Bit patterns
—U811—
00001101
—U224—
00010111
—U400— —U432—
01011001 11000000
*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
Filter
REFHI is tied to pin 1 of U420 and buffered to form BUFF. BUFF through R493, K403, K401,
input protection, and Q421 is tied to the input buffer Q418 and U423. The buffered BUFF signal
(AMP IN) is tied to the FWR, and, being positive, follows the non-inverting, X1 path R452,
Q412, Q411, U417, R453, U410, Q404, and U419 to the filter through U412. Output of the filter
R435, R446, R447, C433, C434, C432, and U426 is tied to U414 pin 5, and the output of U414
is tied to the A/D buffer through buffer U403, R434, R462, and U222. The A/D buffer is config-
ured for X1 gain.
Analog Board; 2002-100
U410, U412, U417, U419, U420, U423, U426, and associated components.
—U811—
00001101
—U224—
00010111
—U400— —U432—
01011001 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—
10111001
Q Q Q Q
87654321 87654321
Bit pattern*
—U810—
00000011
—U206—
01110000
—U203—
10001110
—U411—
11111001
Q Q Q Q
87654321 87654321
Troubleshooting
Register
—U809— AD_STB
11100111
—U207— MUX_STB
11001111
—U221— R1_STB
11101001
—U406— R2_STB
10101110
Register
—U809— AD_STB
11100111
—U207— MUX_STB
11001111
—U221— R1_STB
11101001
—U406— R2_STB
10101110
2-95