Agilent Technologies 83438A - Manual (Page 71)

5-17
Servicing
Troubleshooting
To check the A2A2 Laser Modulation Board Assembly
1 Check the +5V supply by probing the center pin of J11. The modulation input
cable from the rear panel connects to this jack.
2 Check the –15V supply by probing any of the three resistors that are located
next to J2. These resistors are loaded in a straight line and have the label “1471”
printed on them.
3 Locate the large 3W black resistor on the assembly that is closest to the pump
laser.
4 Measure the voltage on the end of the resistor that is furthest from the pump
laser. The voltage should measure approximately –1V to –2V.
5 The pump laser is being driven by the current source and should be turned on.
6 Press the front-panel ACTIVE key so that the front-panel ACTIVE light is turned
off. The voltage measured at the 3W resistor should now be approximately
+0.7V.
The pump laser is turned off.
7 If the voltage measured across the resistor is incorrect, return the instrument
to Agilent Technologies for servicing.