Optical Port (Serial Rs232 Interface); Input Channel 1 And 2 Voltage Measurements - Fluke 43B Service Manual

7.5.5 Optical Port (Serial RS232 Interface)

Receive (RXD)
1. Check the voltage RXDA on TP522 for +200 mV, and the voltage RXD on TP527
(buffered and amplified RXDA voltage) for +3.3V.
2. Shine with a lamp in the optical port (H522).
Check the voltage RXDA on TP522 for 0...-0.6V, and RXD on TP527 for 0V.
Send (TXD).
1. Check the voltage TXD on TP521 for +3.3V.
2. Press to start the test tool data output.
Check the voltage TXD on TP521 for a burst of pulses (pulses from +2V to +3.3V).
The length of the burst and the pulses depends on the selected baud rate.

7.5.6 Input Channel 1 and 2 Voltage Measurements

1. Reset the test tool (press
2. Select the Scope Roll mode for both input channels:
Press
Press
DC, press
press , press
3. Apply a 1 kHz square wave to Input 1 and Input 2, and change the test tool
sensitivity (V/div) to make the complete square wave visible.
4. Check TP154 (ADC-A) and TP254 (ADC-B) for the signal shown below:
Input positive.
Input zero.
Input negative
A trace amplitude of 1 division results in an 150 mV voltage on TP154/255
Moving the trace position, with a zero input signal, results in a TP154/254 voltage of
about +0.3V (bottom) to +1.4V (top).
If the voltages are not correct, do stwmf 6 to 16; if these stwmf are correct, then
replace the C-ASIC.
If the voltages are correct, the error is most probably caused by the ADC, or ADC
control: continue at step 16.
5. Check TP156 (TRIGA) and TP256 (TRIGB). The TRIGA and TRIGB signals must
be the inverted input signals, with an amplitude of 50 mV per division trace
amplitude.
Moving the trace position, with a zero input signal, results in a TP156/256 voltage of
about +0.4V (bottom) to -0.4V (top).
If the voltages are not correct, do stwmf 6 to 16; if these stwmf are correct, then
replace the C-ASIC.
6. Check the supply voltages +3V3A (+3.3V), -3V3A (-3.3V), and +5VA (+5V).
If not correct trace to the Fly Back converter on the Power part.
and
, , highlight SCOPE and press
(SETUP), highlight INPUT 2 Coupling: OFF, press
, highlight Time Base: NORMAL, press
BACK.
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0.3 to 1.4V 150 mV/div
Corrective Maintenance
7.5 Miscellaneous Functions
, highlight
, highlight ROLL,
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