Corrective Maintenance
7.5 Miscellaneous Functions
7
7-9
3. Check TP552 (FLYGATE) for a square wave voltage of at least some volts (for a
correct Fly Back Converter 50...100 kHz, ≅10 Vpp).
a. If a square wave is present on TP552 (may be not the correct value), then:
1. Check the voltage on N501 pin 55 (FLYSENSP). For a correct converter
this is a saw tooth voltage of 50...100 kHz, 50...150 mVpp).
}
50...150 mV
a. If no sawtooth voltage is present on R501, no current, or a DC current
flows in FET V554. The primary coil or V554 may be defective (or
interrupted connections). Check R504, R506, R507 (battery current
sense resistors); these resistors may be fused due to a short in FET
V554.
b. If an incorrect sawtooth is present on R501 this can be caused by:
-overloaded outputs (Frequency low, e.g. <<50 kHz; 250 mVpp)
-underloaded outputs (Frequency high, e.g. >>100 kHz; <<100 mVpp)
-bad FET V554 (Sawtooth voltage is not linear).
2. Check V552 and V553, check R570 and VCOIL connections.
b. No FLYGATE square wave is present.
Check TP526 (FREQPS) for a 50...100 kHz, 3.3 Vpp square wave. If correct,
then check V552, and V553. If no square wave on TP526, then go to step 4.
4. Check TP528 (PWRONOFF) for +3V. If not correct, see 7.5.13 Power ON/OFF.
5. Check N501 pin 43 (COSC) for a triangle waveform, 50...100 kHz, +1.6V to +3.2V.
If not correct check C553 and connections; check IREF, see step 6. If all correct,
replace N501.
6. Check N501 pin 74 (IREF) for 1.6V. If not correct:
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.
7. Check N501 pin 51 (VOUTHI) for <2.5V (nominal value 1.65V). If not correct
check R558 and connections to N501; check IREF, see step 6.
8. Check N501 pin 57 (IMAXFLY) for ≅250 mV. If not correct check R559 and
connections to N501; check IREF, see step 6.
7.5.3 Slow ADC
Check the following signals:
1. BATCUR (N501 pin 77), must be {1.63+(6.7 x IBATP)} Volt.
If not correct, replace N501.
Measure IBATP on X503 pin 3 (= N501 pin 9); IBATP senses the battery current.
2. BATVOLT (N501 pin 78), must be {0.67 x (VBAT-3.27)} Volt.
If not correct, replace N501.
Measure VBAT on TP504 (= N501 pin 3); VBAT senses battery the voltage.
3. BATTEMP (N501 pin 79), must be {TEMP - IBATP} Volt.
If not correct, replace N501.
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