Thermocouple Replacement - HP 3400A Operating And Service Manual

i. Connect the power supply and 1 Kohm resistor between the clear
lead on R4 and pin 14 on the A6 socket. This checks the TC402
output voltage. Refer to Figure 5-5 and connect the HI lead of the
multimeter to point A and the low lead to point B (i.e., across the
resistor). Turn the power supply on and adjust it for a5 V reading
on the multimeter.
j. Disconnect the multimeter and connect as in step f.
k. Make sure the multimeter reading is negative and within 1 mV of the reading noted
in step g. It should display between +6.5mV and +9 mV. If the reading is out of the specified
limits, replace the thermocouples.
5-38. Thermocouple Replacement
5-39. Should a thermocouple be defective, it is necessary to replace both as a matched pair
(see Section VII, Table of Replaceable Parts) for part number. To replace thermocouples,
perform the following steps: ;
to expose the four nuts holding the thermocouple shield.
e. Remove four shield nuts; lift shield off.. Remove thermocouples, noting orientation.