Fluke 123B/S Service Manual - Page 116

Starting Fault Finding., 3 Charger Circuit, Check N501 pin 12 NETVALID for +2.7V

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123/124 Service Manual 7.2 Starting Fault Finding. After each step, continue with the next step, unless stated otherwise. Power the test tool by the battery pack only, then by the power adapter only. 1. The test tool operates with the power adapter, but not with the battery only: install a charged battery (VBAT >4V), and check the connections between the battery and the test tool (X503, R504, R506, R507). 2. The test tool operates with the battery pack, but not with the power adapter only, and the battery pack is not charged by the test tool: continue at 7.3 Charger Circuit. 3. The test tool operates neither with the battery pack, nor with the power adapter: continue at 7.4 Starting with a Dead Test Tool. 4. Particular functions are not correct: continue at 7.5 Miscellaneous Functions. Table 7-1. Starting Fault Finding Power adapter Battery Pack Check 1 OK 2 NOT OK 3 NOT OK 4 Partly OK NOT OK OK NOT OK Partly OK Battery pack, connector, sense resistors See Section 7.3 Charger Circuit See Section 7.4 Starting with a Dead Test Tool See Section 7.5 Miscellaneous Functions 7.3 Charger Circuit 1. Power the test tool by the power adapter only. 2. Check TP501 for ≅15...20V. If not correct, check the power adapter input circuit (X501, Z501,V501, C501). 3. Check TP504 (VBAT) for about 7.5V. If not correct, check R501, V504, V503, L501, C503. Check TP502 for a 100 kHz, 13Vpp pulse signal; if correct or low, check if TP504 is shorted to ground, and check V506. 4. Install a charged battery. The voltage at TP504 will be now about 5V. 5. Check N501 pin 18 (P7VCHA) for ≅7V. If not correct, check N501 pin 20 for ≅15V (supplied via R502). If 15V on pin 20 is correct, check C507, replace N501. P7VCHA is the supply voltage for the charger control circuit in N501. It is derived from VADAPTER (pin20), by an internal linear supply in N501. 6. Check N501 pin 12 (NETVALID) for +2.7V, and TP529 (MAINVAL) for +3.3V. The NETVALID and MAINVAL signals indicate to the P-ASIC and the D-ASIC that a correct power adapter voltage is connected. The signals enable control of the PASIC CHARGE circuit (controls V506 by 100 kHz, 13Vpp square wave). If correct continue at step 7. 7-4

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Service Manual
7-4
7.2 Starting Fault Finding.
After each step, continue with the next step, unless stated otherwise.
Power the test tool by the battery pack only, then by the power adapter only.
1.
The test tool operates with the power adapter, but not with the battery only:
install a charged battery (VBAT >4V), and check the connections between the
battery and the test tool (X503, R504, R506, R507).
2.
The test tool operates with the battery pack, but not with the power adapter only, and
the battery pack is not charged by the test tool: continue at 7.3 Charger Circuit.
3.
The test tool operates neither with the battery pack, nor with the power adapter:
continue at 7.4 Starting with a Dead Test Tool.
4.
Particular functions are not correct: continue at 7.5 Miscellaneous Functions.
Table 7-1. Starting Fault Finding
Power adapter
Battery Pack
Check
1
OK
NOT OK
Battery pack, connector, sense resistors
2
NOT OK
OK
See Section 7.3 Charger Circuit
3
NOT OK
NOT OK
See Section 7.4 Starting with a Dead Test Tool
4
Partly OK
Partly OK
See Section 7.5 Miscellaneous Functions
7.3 Charger Circuit
1.
Power the test tool by the power adapter only.
2.
Check TP501 for
≅
15...20V.
If not correct, check the power adapter input circuit (X501, Z501,V501, C501).
3.
Check TP504 (VBAT) for about 7.5V.
If not correct, check R501, V504, V503, L501, C503.
Check TP502 for a 100 kHz, 13Vpp pulse signal; if correct or low, check if TP504 is
shorted to ground, and check V506.
4.
Install a charged battery.
The voltage at TP504 will be now about 5V.
5.
Check N501 pin 18 (P7VCHA) for
≅
7V.
If not correct, check N501 pin 20 for
≅
15V (supplied via R502).
If 15V on pin 20 is
correct, check C507, replace N501.
P7VCHA is the supply voltage for the charger control circuit in N501.
It is derived from
VADAPTER (pin20), by an internal linear supply in N501.
6.
Check N501 pin 12 (NETVALID) for +2.7V, and TP529 (MAINVAL) for +3.3V.
The NETVALID and MAINVAL signals indicate to the P-ASIC and the D-ASIC that a
correct power adapter voltage is connected.
The signals enable control of the P-
ASIC CHARGE circuit (controls V506 by 100 kHz, 13Vpp square wave).
If correct continue at step 7.