Troubleshooting The Serial Eeprom - Fluke 39 Service Manual

2. Verify that U3 is producing the correct INC_EEPOT and CS_EEPOT signals as
shown in the following timing diagram. EE_UPLOW (U8-2) controls the direction
that the WIPER will move. CS_EEPOT (U8-7) selects the EEPOT. When the
CS_EEPOT signal goes from low to high, thus deselecting the EEPOT, the present
value of the EEPOT is saved to nonvolatile memory and will be used as EEPOT's
default value upon receiving power. Once the EEPOT is selected, INC_EEPOT (U8-
1) is pulsed low to increment/decrement the wiper position in accordance with the
EE_UPLOW line. If the signals EE_UPLOW, CS_EEPOT, and INC_EEPOT are
correct to U8, but the wiper does not move or the part does not save the result, U8
may be defective. If the CS_EEPOT or the INC_EEPOT* signals are not generated
properly, verify that all the correct signals are present on U3. (A15, A14, A5, A4,
RD, WR, XY, PS). If they are, U3 may be defective.
DSPCLCK
_CS_LCD
_INC_EEPOT
_CS_EEPOT

5-12. Troubleshooting the Serial EEPROM

A faulty serial EEPROM is indicated if upon power-up, the Tester displays
"CALIBRATION ERROR" or the contrast adjustment is not retained after the Tester has
been calibrated and the power has been cycled off/on. To further isolate the problem,
proceed as follows:
During calibration, the CALIBRATION ERROR message will not
disappear until power is cycled.
1. Display the power-up configuration screen by holding
multiple menu items are highlighted on a line or no menu items on a given line are
highlighted, the serial EEPROM (U22) is probably faulty.
In the next step, the Fluke 39 will not display the baud rate or printer type.
2. Reset the instrument to factory default by holding R and pressing O. Then,
power the Tester off and back on to bring up the power-up configuration screen. The
following menu items should be highlighted: VOLT, WAVE, %RMS, 80I-500S,
VOLT, 9.6K, and EPSON. If these menu items are not highlighted, the serial
EEPROM (U22) may be defective.
The serial EEPROM signals will be active just after the last step is
completed in the power-up configuration screen.
3. When the serial EEPROM (U22) is read from or written to, the following conditions
should be present:
•
CS_EESER should be low (U22-1).
Troubleshooting the Digital Section
Note
E
Note
Note
Troubleshooting
t22i.eps
O
and pressing . If
5
5-13