Regulator And Switching Tests - Keithley 2002 Repair Manual

Troubleshooting

2.11.17 Regulator and switching tests

Test 401.1 — Regulator
Type
Fault message
Description
Drawing reference
Components
Bit patterns
Test 402.1 — Frequency switch
Type
Fault message
Description
Drawing reference
Components
2-70
Pass/Fail
Regulator
COMMON is routed to the ACF line through U428 (SHORT control line is pulled low). ACF
then goes to multiplexer U414 pin 8 and follows the same path to the A/D buffer as the 400 level
tests. U226 is set up for X1 gain.
Analog Board; 2002-100
U403, U414, U418, and associated components.
—U811—
00001101
—U224—
00010111
—U400— —U432—
01111011 00010111
*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
Frequency switch
U433 (DAC B) is set up to output 4.48V at PRECOMP+, U430 pin 1. The operation of the fre-
quency switch, U425 (FREQ control line pulled low), is verified by dividing the PRECOMP+
voltage by the ratio of R491 and R440. The on resistance of U425 (about 25Ω between pins 2
and 3 must also be added to R440 as this value is also part of the ratio). Again, as in the 400 level
tests, this voltage is routed to the A/D buffer, and U226 is set up for X1 gain.
Analog Board; 2002-100
U403, U425, U430, U433, and associated components.
Bit pattern*
—U810—
00000011
—U206—
01110000
—U203—
10001110
—U411—
10111011
Q Q Q Q
87654321 87654321
Register
—U809— AD_STB
11100111
—U207— MUX_STB
11001111
—U221— R1_STB
11101001
—U406— R2_STB
00000101