Keyboard - Fluke 43B Service Manual

43B
Service Manual
4. +3V3SADC must be +3.3V (supplied by N501 pin 65). If not correct, check if the
5. SELMUXn (TP591, TP592, TP593) supplied by the D-ASIC must show LF pulses
6. Check TP536, TP537, and TP534 for signals shown below (typical examples,

7.5.4 Keyboard

Proceed as follows if one or more keys cannot be operated.
1. Replace the key pad, and the key pad foil to see if this cures the problem.
2. Press a key, and check ROW0...5 (measure spots MS432..MS437) for the signal
If no key is pressed the ROW lines are low if a battery is installed; if the 43 is powered
3. Check COL0...3 (measure spots MS438...MS441) for a +3.3V level. Then press and
For the ON/OFF key see 7.5.13.
7-10
Measure TEMP on N501 pin 5 (=X503 pin 6); TEMP senses the battery temperature.
Measure IBATP on X503 pin 3 (= N501 pin 9); IBATP senses the battery current.
+3V3SADC line is shorted to ground. If it is not, then replace N501.
(0V to +3.3V, 0.5...3 seconds period).
measured signals may have different pulse amplitude and repetition rate).
TP536: if at a fixed level, replace D531.
TP537: if not correct, trace signal to PWM circuit on the Digital part.
TP534: if at a fixed level, replace N531.
≈+3V
TP536
0V
≈ 500 ms
shown below :
+3.3V
0V
Press key
by the the mains adapter only, the lines are alternating pulsing and low.
hold a key, and check the matching COL line for the signal shown below:
+3.3V
0V
Press key
If not correct, check the connections from X452 to D471; replace D471.
TP537
≈+0.5V
≈ 50 ms 500 µs pulses
≈ 50 ms 500 µs pulses
TP534
Release key
Release key