Keithley 2002 Repair Manual page 118

Bit patterns
Test 500.6 — 200mA DCA range
Type
Fault message
Description
Drawing reference
Components
Bit patterns
—U811—
00001101
—U224—
00001111
—U400— —U432—
01111011 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.
Pass/Fail
200mA DCA range
The 7.2mA ohms source is switched in using the /OHMA control line at U223 and U220. U232
pin 2 to 3 connects the REFBUF to U233 pin 3. The 7.2mA current divides between Q211 and
Q212, then flows through Q213, R322, CR217, K201,R334 and R342. This point is the HI input
terminal to the DMM. The HI to AMPS jumper routes the current to the AMPS line through the
200mA range (Q222 and Q215 on), through R319, and R362 to common. 7.2mA through 1Ω
generates 0.0072V at U225 pin 3. U225 is at unity gain so the same voltage is at DCA. DCA is
switched through U222 to the A/D MUX U226, and the gain is X50.
NOTE: INPUT HI and AMPS must be externally jumpered to run this test.
Analog Board; 2002-100
U220, U222, U223, U225, U226, U232, U233, and associated components.
—U811—
00001101
—U224—
01011111
—U400— —U432—
01111011 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—
11010000
—U203—
10001110
—U411—
11111011
Q Q Q Q
87654321 87654321
Bit pattern*
—U810—
00000011
—U206—
11010000
—U203—
10001110
—U411—
11111011
Q Q Q Q
87654321 87654321
Troubleshooting
Register
—U809— AD_STB
11100111
—U207— MUX_STB
10101111
—U221— R1_STB
01110111
—U406— R2_STB
00000100
Register
—U809— AD_STB
11100111
—U207— MUX_STB
10101111
—U221— R1_STB
01110111
—U406— R2_STB
00000100
2-105