Agilent Technologies 5517B Operation And Service Manual page 96

f. If ending troubleshooting procedures at this point, disconnect power from HP5517B/C/D Laser
Head, set all test jumpers to their left-most (normal) positions, and replace laser head front panel and
side covers.
8-141. Liquid Crystal Troubleshooting
8-142. This procedure assumes that the digital, the photodiode, and the amplifier circuits are all functioning
properly.
A TILDE ("-") PRECEDING ALL SIGNALS INDICATES NEGATIVE-TRUE LOGIC.
a. Verify that laser beam is on. Set all test jumpers (except LIQUID CRYSTAL) on A3 to their left-most
positions. Set LIQUID CRYSTAL to PASS. Insert test polarizer (HP Part Number 1000- 0616) between
laser assembly and sampler assembly. The bottom edge of the polarizer should be parallel to the base
of the HP 5517B/C/D. Measure A3TP16 voltage. Is it<0.2V? If yes, go to step c. If not, go to step b.
b. Rotate polarizer 90 degrees. Is A3TP16 voltage <0.2 V? If yes, go to step c. If no, go to step f.
c. Rotate polarizer 90 degrees. Is A3TP16 voltage >0.5 V? If yes, go to step d. If not, go to step f.
d. Keeping test polarizer in same position as in step c, set LIQUID CRYSTAL jumper to ACT. Is A3TP16
voltage <0.2 V? If yes, go to step e. If not, go to step f.
e. Rotate polarizer 90 degrees. Is A3TP16 voltage >0.5V? If yes, the liquid crystal is OK. If no, go to step f.
f. Liquid crystal may not be working. See paragraph 8-71 (Liquid Crystal Test). Ensure that the
elastomeric connectors are connecting the A4 Assembly with the liquid crystal.
If contact problems develop, remove elastomeric connectors and clean both sets of contacts at A4 and the liquid
crystal with isopropyl alcohol. Reinstall the elastomeric connectors (HP Part Number 8160-0530) in the A4
assembly.
g. If ending troubleshooting procedures at this point, disconnect power from HP5517B/C/D Laser
Head, set all test jumpers to their left-most (normal) positions, and replace laser head front panel and
side covers.
8-143. Subtracting Sample and Hold Troubleshooting
8-144. This procedure assumes that the digital, the photodiode, and the amplifier circuits are all functioning
properly.
A TILDE ("~") PRECEDING ALL SIGNALS INDICATES NEGATIVE-TRUE LOGIC.
a. Set -REF ON jumper to LO and HTR OK to HI. Wait for READY LED to remain on. Set HTR OK to
NRM. Set PHOTO DIODE jumper to TEST and LIQUID CRYSTAL jumper to ACT. Using a dedicated
DC voltmeter, check that the voltage at A3TP16 is between -50 mV and +50 mV? If yes, go to step c.
If no, go to step b.
b. The circuitry connected to Pin 2 or Pin 15 (outputs) of A3U12 is incorrectly loading photodiode amp
when switch A3U12A or A3U12D is closed. Check A3U11, C13, and C14.
c. Is voltage at A3TP13 equal to voltage at A3TP16 within 10 mV? If no, go to step d. If yes, go to step e.
d. Verify A3U12 (Pin 8) is low. Measure voltage from A3U11B (Pin 5) to A3TP13. Is it between -10 mV
and +10 mV? If yes, go to step i. If no, A3U11 B is defective or its output is incorrectly loaded.
e. Is voltage at A3TP14 equal to voltage at A3TP16 within 10 mV. If yes, go to step g. If no, go to step f.
NOTE
NOTE