Overload Tests - Keithley 2002 Repair Manual

Troubleshooting

2.11.15 Overload tests

Test 308.1 — Overload HI
Type
Fault message
Description
Drawing reference
Components
Bit patterns
2-64
Pass/Fail
Overload HI
2VREF is switched through U222 to U226. The A/D MUX is configured for X50 gain. This con-
dition saturates U226 at the positive rail of about 13V. R231, R230, R229, and R228 form a di-
vider that outputs 11V to pin 9 of comparator U214 and -11V to pin 6 of U214. A/D_IN, which
is about at 13V, at pin 8 of comparator U214 results in /OVLD_HI being pulled low at about -
15V. All of the OVLD lines are latched by U202, parallel loaded into U201, and serially input
to the A/D board at J1026 pin 15. There is no A/D measurement for this test. The pass/fail criteria
is based on the value of the /OVLD_HI bit.
Analog Board; 2002-100
U214, U222, U226, and associated components.
—U811—
00001101
—U224—
00010111
—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
Register
—U809— AD_STB
11100111
—U207— MUX_STB
01001111
—U221— R1_STB
11101001
—U406— R2_STB
00000100