Laser Tube Current Adjustment - HP 5501B Operating And Service Manual

5-17. Laser Tube Current Adjustment

A TILDE ("~") PRECEDING A SIGNAL NAME INDICATES NEGATIVE-
TRUE LOGIC LEVELS.
5-18. This procedure adjusts the laser tube current to 3.5 milliamperes ± 0.1 milliampere.
Test Equipment Required. The laser current adjustment requires the following test equipment:
Clip-On DC Milliammeter, HP Model 428B
5-19. Procedure to adjust the laser tube current, observe the safety precautions in Paragraph 5-4 and
proceed as follows:
a. Turn the system power supplies OFF.
b. Remove the laser head covers by following the procedures outlined in paragraph 8-55.
c. On the A1 Connector Board, set TEST-NORM (A1S2) switch to TEST. See Figure 5-1.
d. Set indicated jumpers to the following positions:
1.
2.
3.
4.
Setting the A3 jumpers causes the laser to come on soon after power is
applied.
e. Set the milliammeter to the 10 milliampere range.
f. Clip the HP428B probe around the red (Anode) High Voltage Power Supply wire located
underneath the laser tube (See Figure 5-3). The arrow on the milliammeter probe should
point away from the supply. Keep the probe as far as possible from and perpendicular to
the magnet assemblies. It may be necessary to prop up the probe to achieve the
perpendicular orientation.
g. On the milliammeter, adjust for zero indication. If zero indication cannot be obtained,
degauss the probe as directed on the back of the milliammeter.
After the zero setting has been made on the milliammeter, do not move
the probe, this will affect the zero setting.
5-4
JMP2 (~REF ON) .........................LO
JMP4 (HTR OK) ............................HI
JMP7 (HEATER) ...........................OFF
JMP8 (CLK FREQ) ........................HI
NOTE
NOTE
NOTE
HP5501B
Adjustments