Liquid Crystal Troubleshooting; Subtracting Sample And Hold Troubleshooting - HP 5501B Operating And Service Manual

8-142. Liquid Crystal Troubleshooting

8-143. This procedure assumes the digital circuits and the photodiode and amplifier circuit are
functioning properly.
a. Set A1S2 to TEST. Verify laser is on. Set all jumpers on A3 to left except LIQ CRYS 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
HP5501B. Measure TP16 voltage. Is it <0.2V? If yes, go to step c. If not, go to step b.
b. Rotate polarizer 90 degrees. Is TP16 voltage <0.2V? If yes, go to step c. If no, go to step
f.
c. Rotate polarizer 90 degrees. Is TP16 voltage >0.5V? If yes, go to step d. If not, go to
step f.
d. Set LIQ CRYS jumper to ACT. Is TP16 voltage <0.2V? If yes, go to step e. If not, go to
step f.
e. Rotate polarizer 90 degrees. Is TP16 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 8-61, Liquid Crystal Test. Check that
the elastomeric connectors are connecting A4 and 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 A4
Assembly.

8-144. Subtracting Sample and Hold Troubleshooting

8-145. This procedure assumes the digital circuit and photodiode and amplifier are functioning properly.
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 LIQ CRYS jumper to ACT.
Using a dedicated DC voltmeter, check that the voltage at TP16 is -50 mV to +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 U12 is incorrectly loading
photodiode amp when switch U12A or U12D is closed. Check U11, C13, and C14.
c. Is voltage at TP13 equal to voltage at TP16 within 10 mV? If no, go to step d. If yes, go to
step e.
d. Verify U12 (Pin 8) is low. Measure voltage from U11B (Pin 5) to TP13.ls it -10 mV to +10
mV? If yes, go to step i. If no, U11 B is defective or its output is incorrectly loaded.
e. Is voltage at TP14 equal to voltage at TP16 within 10 mV? If yes, go to step g. If no, go to
step f.
f. Verify U12 (Pin 9) is low. Measure voltage from U11 C (Pin 10) to TP14. Is it -10 mV to
+10 mV? If yes, go to step i. If no, U11C is defective or its output is incorrectly loaded.
g. Set POWER AMP jumper to UP. Is voltage at TP12 between -20 mV and +20 mV? If yes,
go to step i.1f no, go to step h.
h. Verify U11A (Pin 3) voltage is about 1/2that of TP13 voltage. Verify U11A (Pin 2) voltage
= U11A (Pin 3) voltage. If not, U11A, R10, R12, R14, or R15 may be bad.
8-42
NOTE
HP5501B
Service