Fluke 900 - Manual (Page 80)

Maintenance FLUKE 900 SERVICE MANUAL
5.2 Performing Adjustments
5.2.1 Adjustment to Vcc
The Vcc level is adjustable over a narrow range around 5.0 volts from a potentiometer on the
power supply module.
With the unit face-down and power off, remove the four screws from the bottom
of the unit which hold the upper and lower halves together. Turn the unit face-up.
The right side of the top ¿¿f may be raised up and to the left, somewhat like
opening a book, while still maintaining electrical connections between the two
halves. This permits access to the PS potentiometer.
Power up the unit and wait for a successfiil selftest.
FoUow the procedure outlined at the end of Section 5.1 to enter the Engineering
Menu and display the Vcc value. The potentiometer may be reached through a
hole in the top of the power supply cover. It is located in the middle of the edge
closest to the center of the unit The value should be set to about 5.02 to be within
the limits of 5.00 to 5.04 volts.
5.2.2 Adjustment to Display Contrast
The display contrast is adjustable from a potentiometer on the Micro Board.
With the unit face-down and power off, remove the four screws from the bottom
of the unit which hold the upper and lower halves together. Turn the unit face-up.
The right side of the top h^f may be raised up and to the left, somewhat like
opening a book, while stiU maintaining electrical connections between the two
halves. This permits access to the potentiometer.
Power up the unit and observe the main screen while turning the potentiometer
located on the Micro Board near the Display Controller connector.
5.2.3 Changing System Firmware
The main screen after a successful power up selftest indicates the system firmware revision on
the left and the library firmware revision on the right. System firmware resides on 4
EPROMs, standard library firmware on a single EPROM and custom library firmware on a
single EPROM (eg. Simulation Library for Sales Demo UUT).
Remove the Micro Board as described in Section 5.3.
Remove the existing EPROMs and insert new ones according to the following list:
5-2