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Troubleshooting
2-60
Bit patterns
Test 305.4 — 20V range multiplexer signal
Type
Pass/Fail
Fault message
20V range MUX signal
Description
The ohms source is in the same configuration as test 304.1 to create 6V at input HI, which is the
HI input terminal to the DMM. This signal is then switched through the Q246, Q245, Q244 path
to BUFFIN. Q205 is turned on so that the signal reaches R240, and Q203 is always on because
its gate and source are tied together by R241. 3V appears at U217 pin 3. Since U217 is a unity-
gain buffer, 3V also appears at R261, and U222 switches pin 7 to pin 3 of U226. X1 gain is
achieved by closing U227 pins 2 to 3 with /X1 low, and R274 is in the feedback path of U226.
Drawing reference
Analog Board; 2002-100
Components
Q205, U217, U222, U226, U227, and associated components.
Bit patterns
Bit pattern*
Register
—U400—
01111011
—U811—
00001101
—U224—
00010111
—U432—
10000000
—U810—
00000011
—U206—
01110100
—U203—
10001110
—U411—
11111011
—U809—
11100111
—U207—
00001111
—U221—
11101001
—U406—
00000100
AD_STB
MUX_STB
R1_STB
R2_STB
*Bits associated with register IC terminals as follows:
Q
Q
Q
Q
Q
Q
Q
Q
87654321
87654321
87654321
87654321
IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.
Bit pattern*
Register
—U400—
01111011
—U811—
00001101
—U224—
00010111
—U432—
10000000
—U810—
00000011
—U206—
01111000
—U203—
11110100
—U411—
11111011
—U809—
11100111
—U207—
01101111
—U221—
01110111
—U406—
00000100
AD_STB
MUX_STB
R1_STB
R2_STB
*Bits associated with register IC terminals as follows:
Q
Q
Q
Q
Q
Q
Q
Q
87654321
87654321
87654321
87654321
IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.
Содержание 2002
Страница 1: ...Model 2002 Multimeter Repair Manual Contains Servicing Information...
Страница 125: ...Troubleshooting 2 112...
Страница 145: ...A Specifications A 1...