Agilent Technologies 5517B Operation And Service Manual page 97

f. Verify A3U12 (Pin 9) is low. Measure voltage from A3U1 IC (Pin 10) to A3TP14. Is it between -10 mV
and +10 mVnf yes, go to step i. If no, A3U11C is defective or its output is incorrectly loaded.
g. Set POWER AMP jumper to UP. Is voltage at A3TP12 between -20 mV and +20 mV? If yes, go to step
i. If no, go to step h.
h. Verify A3U11A (Pin 3) voltage is about 1/2 that of A3TP13 voltage. Verify that A3U11A (Pin 2)
voltage equals the A3U11A (Pin 3) voltage. If not, A3U11A, R10, R11, R14, or R15 may be bad.
i. Place LIQUID CRYSTAL jumper to NRM. A3TP16 will alternate between approximately 0V and -5V.
Record these voltages (the "AV" function of the HP 5005A/B is useful here). Measure voltage at
A3TP13. It should be within 20 mV of the same approximate -5 V reading as at A3TP1 6. If OK, go to
step k. if not, go to step j.
J. Measure the voltage on A3C13. During and just after the switch (A3U12A) is closed (DELAYED ACTIVE signal
on Test IC A3U5 (Pin 11)), the voltage should equal the approximate -5 Volts at A3TP16. If not, or if the voltage
rapidly goes to zero, then A3C13 is shorted or the switch A3U12A does not work. Also check that A3U12B is open
and A3U11 B is not shorting this node.
k. Is the voltage at A3TP14 within 20 mV of the approximate 0V voltage at A3TP16. If yes, go to step m. If not, go to
step 1.
I. Measure the^voltage on A3C14. During and just after the switch (A3U12D) is closed (DELAYED PASSIVE signal
on Test IC A3U5 (Pin 6)), the voltage should equal the approximate 0 V at A3TP16. If not, or the voltage rapidly
goes to zero, then A3C14 is shorted or A3U12D is faulty. Also check that A3U12C is open and A3U11C is not
shorting this node.
m. Set PHOTO DIODE jumper to TEST, LIQUID CRYSTAL to PASS, POWER AMP to UP. Verify that
A3TP16 voltage is approximately -5V. Measure voltage at A3TP14 and record as V14. Measure
voltage at A3U11A (Pin 3) and record as V3 . Measure voltage at A3TP12. Is it equal to [2x V3] - V14
within 30 mV? If yes, go to step o. If no, go to step n.
n. Verify A3U11A (Pin 2) is at the same voltage as A3U11A (Pin 3). If not, A3U11A or A3R15 bad. Also check
A3R14, R10, and R11.
o. This procedure thus far has shown that the Subtracting Sample and Hold circuitry works during optical mode.
Next the operation during warm-up is checked. Remove power from HP 55178/01). Move all A3 jumpers to NRM. Set
-REF ON to HI. Connect an ohm meter between Pins 6 and 7 of check for opens in either A3R32, R40, C20, or CR3.
Also check for a shorted A3R33. In addition, check the integrity of resistors A3R49, RSO, or R51. If the jump is <4.5
V, check for a short in resistors A3R32, R40, R41 or diodes CR3 and CR4. Also check for an open in resistor A3R39.
Check the integrity of resistors A3R49, R50, and R51. If the ramping is too slow or too fast, check components
A3R33, R49, R50, R51 and C20. If OK, go to step h.
h. When A3TP11 voltage is >+13 V, measure voltage from A3TP11 to A3TP17. If it measures between
5.7V and 6.7V, go to step i. If it is >6.7V, then A3CR4 is open. If it is <5.7V, then either A3R40, R41,
or CR4 is shorted. Check A3R39 for an open.
i. Set HEATER jumper to OFF. Voltage at A3TP11 should measure between +0.2V and +0.6V. If so, the
power amp is OK. If it is <+0.2 V, A3R9 is open.
j. Set POWER AMP to UP, HEATER jumper to NRM. Wait for A3U13 (Pin 6) to be >+13 V. Measure voltage at
A3Q5 base. If it is >+1 V, go to step k. If it is <+1 V, A3R36 may be open.
k. Measure voltage across A3R37. If it measures zero, then A3Q5 or A3R38 is open. If it is greater than + 1 V then
A3C20, A3R39, or the laser head heater is shorted. Check A3Q3 orA3R33 for opens. Ensure that A3R21 and A3U14
are not loading down this node
I. Set POWER AMP jumper to DWN. Wait for A3U13 (Pin 6) to measure <-10 V. Measure voltage at A3Q5 base If it
is >1 V, then A3Q5 is shorted. If it is < 1 V, go to step m.
m. Measure voltage across A3R37. If it is >1 V, then A3Q5 is shorted or A3R37 open. If it is zero, then A3Q3 or A3R9
is shorted or the heater is open.
n. If ending troubleshooting procedures at this point, disconnect power from HP 5517B Laser Head, set all test
jumpers to their left-most (normal) positions, and replace laser head front panel and side covers.