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Troubleshooting

2-105

Bit patterns

Test 500.6 — 200mA DCA range

Type

Pass/Fail

Fault message 200mA DCA range

Description 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.

Drawing reference Analog Board; 2002-100

Components U220, U222, U223, U225, U226, U232, U233, and associated components.

Bit patterns

Bit pattern* Register

—U400—

01111011

—U811—

00001101

—U224—

00001111

—U432—

10000000

—U810—

00000011

—U206—

11010000

—U203—

10001110

—U411—

11111011

—U809—

11100111

—U207—

10101111

—U221—

01110111

—U406—

00000100

AD_STB

MUX_STB

R1_STB

R2_STB

*Bits associated with register IC terminals as follows:

QQQQQQQQ

87654321 87654321 87654321 87654321

IC pins: Q8=11, Q7=12, Q6=13, Q5=14, Q4=7, Q3=6, Q2=5, Q1=4.