HP5501BAdjustments5-45-17. Laser Tube Current AdjustmentNOTEA 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 428B5-19. Procedure to adjust the laser tube current, observe the safety precautions in Paragraph 5-4 andproceed 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. JMP2 (~REF ON) .........................LO2. JMP4 (HTR OK) ............................HI3. JMP7 (HEATER) ...........................OFF4. JMP8 (CLK FREQ) ........................HINOTESetting the A3 jumpers causes the laser to come on soon after power isapplied.e. Set the milliammeter to the 10 milliampere range.f. Clip the HP428B probe around the red (Anode) High Voltage Power Supply wire locatedunderneath the laser tube (See Figure 5-3). The arrow on the milliammeter probe shouldpoint away from the supply. Keep the probe as far as possible from and perpendicular tothe magnet assemblies. It may be necessary to prop up the probe to achieve theperpendicular 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.NOTEAfter the zero setting has been made on the milliammeter, do not movethe probe, this will affect the zero setting.
