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Troubleshooting

2-95

Bit patterns

Test 411.2 — Filter; variable gain ampliﬁer

Type

Pass/Fail

Fault message Filter

Description REFHI is tied to pin 1 of U420 and buffered to form BUFF. BUFF through R493, K403, K401,

input protection, and Q421 is tied to the input buffer Q418 and U423. The buffered BUFF signal

(AMP IN) is tied to the FWR, and, being positive, follows the non-inverting, X1 path R452,

Q412, Q411, U417, R453, U410, Q404, and U419 to the ﬁlter through U412. Output of the ﬁlter

R435, R446, R447, C433, C434, C432, and U426 is tied to U414 pin 5, and the output of U414

is tied to the A/D buffer through buffer U403, R434, R462, and U222. The A/D buffer is conﬁg-

ured for X1 gain.

Drawing reference Analog Board; 2002-100

Components U410, U412, U417, U419, U420, U423, U426, and associated components.

Bit patterns

Bit pattern* Register

—U400—

01011001

—U811—

00001101

—U224—

00010111

—U432—

11000000

—U810—

00000011

—U206—

01110000

—U203—

10001110

—U411—

10111001

—U809—

11100111

—U207—

11001111

—U221—

11101001

—U406—

10101110

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.