Test Tool Software Does Not Run; Software Runs, Test Tool Not Operative; Miscellaneous Functions; Display And Back Light - Fluke 43B Service Manual

TP307 (N501 pin 72, REFP) for 1.22V, check V301/R307. If no 1.22V, and
V301/R307 and connections are correct, then replace N501.
c. Check N501 pin 12 (NETVALID) for +2.6V. If not correct, proceed as
indicated in 7.3, step 6.
d. Check the Power ON/OFF function, see 7.5.13.
6. Check X-tal signals on TP473 (32 kHz), and TP476 (25 MHz); if not correct check
connections, replace X-tals, replace D471. The 16 MHz clock on TP474 runs only if
the test tool software runs. If the 16 MHz clock is present, then continue at 7.4.3.

7.4.2 Test Tool Software Does not Run.

1. Turn the test tool OFF and ON again.
2. Check D471 pin 59 (row1) for a 100 kHz square wave.
If no 100 kHz is not present, but you heard a weak beep, the test tool software runs,
but the buzzer circuit does not function correctly. Go to 7.5.10 to check the buzzer
circuit, then continue at 7.4.3 to see why the test tool cannot be operated.
If a 100 kHz square wave is present, the MASK software is running. Continue at 3.
3. Check TP487 (ROMRST) for >3V.
4. Load new software to see if the loaded software is corrupted. See 7.6.
5. Do the RAM test, see 7.5.12.
6. Check for bad soldered address/data lines and IC pins.
7. Replace FLASH-ROM D474 and RAM D475.

7.4.3 Software Runs, Test Tool not Operative

1. Check the Display and Backlight function, see 7.5.1
2. Check the Fly Back Converter, see 7.5.2
3. Check the Keyboard function, see 7.5.3

7.5 Miscellaneous Functions

7.5.1 Display and Back Light

The voltage for the LCD back light fluorescent lamp is >400V!
1. Connect another LCD unit to see if the problem is caused by the LCD unit. The unit
is not repairable.
2. Defective display
Check the LCD control signals on measure spots MS401...MS422 (near to X453).
Use a 10:1 probe with ground lead on the probe connected to the metal screening of
the UUT. Notice that MS407 is missing !
a. MS422:
b. MS420:
MS414-415:
Warning
LCDONOFF for +3.3V.
DATACLK0 for 120 ns pulses
LCDAT0,1 for 250 ns pulses
Corrective Maintenance

7.5 Miscellaneous Functions

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