Table 8-1. A3U9 Test Ic Signal Summary - HP 5501B Operating And Service Manual

8-49. BUILT-IN TEST AIDS
8-50. Several jumpers are included to aid in testing. The RESET jumper, JMP1, places the state
machine in a repetitive mode to allow signature measurements. The ~REF ON jumper, JMP2,
sets the ~REF ON signal so that U17 cannot influence the state machine. LIQ CRYS jumper,
JMP3, places the liquid crystal in either the active or passive state. The HTR OK jumper, JMP4,
sets the HTR OK signal so that U15 cannot influence the state machine. JMP5, PHOTO DIODE,
substitutes a known current for the photodiode and is used for testing the photodiode amplifier
and the subtracting sample and hold circuits. JMP6, POWER AMP, supplies ±100 mV to U13
(Pin 3) to test the power amplifier. JMP7, HEATER, disables the power amplifier. The CLK FREQ,
JMP8, allows the clock circuitry to generate either of the following three clock rates: NRM = 100
Hz, HI = 1000 Hz, and with the jumper removed completely =75 kHz. Test IC U9 is dummy 16-
pin DIP package with no integrated circuit. All of the important digital signals connect to U9 so
that a logic clip can be used for monitoring.
There are two "LO" positions for the REF ON jumper, and two "UP"
positions for the POWER AMP jumper. For proper placement, refer to
the schematics for A3 when using these jumpers.
8-51. The following is a summary of the signal functions on U9:
1, 2, 3, 4
11, 12, 13

Table 8-1. A3U9 Test IC Signal Summary

PIN
Timing of sample and hold during optical mode.
5,6 Timing of sample and hold during warmup mode.
7, 10 Liquid crystal drive
9 Presets digital circuitry
Indicates state of the state machine
14, 15 Inputs to the state machine
NOTE
PURPOSE
HP5501B
Service
8-13