Slow Adc - Fluke ScopeMeter 123 Service Manual

123
Service Manual
4. Check TP528 (PWRONOFF) for +3V. If not correct, see Section 7.5.13 Power
5. Check N501 pin 43 (COSC) for a triangle waveform, 50...100 kHz, +1.6V to +3.2V.
6. Check N501 pin 74 (IREF) for 1.6V. If not correct:
7. Check N501 pin 51 (VOUTHI) for <2.5V (nominal value 1.65V). If not correct
8. Check N501 pin 57 (IMAXFLY) for ≅250 mV. If not correct check R559 and

7.5.3 Slow ADC

Check the following signals:
1. BATCUR (N501 pin 77), must be {1.63+(6.7 x IBATP)} Volt.
2. BATVOLT (N501 pin 78), must be {0.67 x (VBAT-3.27)} Volt.
3. BATTEMP (N501 pin 79), must be {TEMP - IBATP} Volt.
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,
7-10
ON/OFF.
If not correct check C553 and connections; check IREF, see step 6. If all correct,
replace N501.
a. Check N501 pin 73 (REFPWM2) for +3V3. REFPWM2 is supplied by N501,
and derived from REFP on the reference circuit on the Trigger part. Check
TP307 (N501 pin 72, REFP) for 1.22V. If not correct, check V301/R307.
b. Check R528, loose pin 74, or N501 defective.
check R558 and connections to N501; check IREF, see step 6.
connections to N501; check IREF, see step 6.
If not correct, replace N501.
Measure IBATP on X503 pin 3 (= N501 pin 9); IBATP senses the battery current.
If not correct, replace N501.
Measure VBAT on TP504 (= N501 pin 3); VBAT senses battery the voltage.
If not correct, replace N501.
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
TP537
≈+0.5V
TP534