T5n/T4n/T3n
55
Note: The output voltage may be out of the range when it is measured without the load resistance or the power supply voltage
differs from the specified in the table 1-1.
2-3
Discharge (See page 64)
To prevent the electrical shock (discharge of the electric charge from the capacitor), discharge electricity between the follow-
ing part when handling the PST circuit board.
• Between the positive (+) and negative (-) terminals of C124, C125, C126 and C127.
If you have left the unit for 10 minutes or more after turning the power off, you do not have to discharge.
• Between CN105 – CN107 and CN108 – CN110.
• Between the terminals of C101.
3.
Example of Repair
All DC voltage is not output from secondary side.
3-1
Instruction
Follow the instruction below. (See page 64, 65 and 66.)
1
Check the resistor value of R129, R172 and R174 (6.8 ohms, 5 W).
If opened, replace it.
Measuring Part
R129: Resistor value between CN111 and test point A.
R172: Resistor value between CN101 (6 pin) and F101 (primary side).
R174: Resistor value between CN101 (6 pin) and F102 (primary side).
2
Check the resistance between C – E of Q106 and Q107.
If short-circuited or the resistance lowers by several values (ohm), replace it.
Also replace IC103 because it is broken.
3
Check the resistance between C – E of Q113 and Q114.
If short-circuited or the resistance lowers by several values (ohm), replace it.
Also replace IC104 because it is broken.
4
Check the resistor value of R140, R141, R142 and R143 (10 ohms).
If opened or the resistor value increases, replace it.
5
Check the resistor value of R138 and R139 (4.7 ohms).
If opened or the resistor value increases, replace it.
6
Check the resistor value of R166 and R167 (2.2 ohms).
If opened or the resistor value increases, replace it.
7
Remove F101, F102 and then turn the power switch on.
Check the AC voltage between the test point B and C on the component side of PST circuit board is same as the AC power
supply voltage.
Checking the waveform
Note: Do not connect the oscilloscope ground with the ground terminal of the AC plug of this unit when checking the
waveform. Otherwise the component installed in this unit may be damaged.
Measure the waveform between pin 1 (LO) and pin 2 (COM) of IC103 with the oscilloscope.
Note: When measuring the waveform, short-circuited the PR101.
When the measured waveform is approximately 70 kHz, 15 Vp-p square wave, it is normal.
When the measured waveform is not normal, check the voltage between test point 12 pin of IC101 and D is approximately
+16 V. When measured voltage is +15 V or less, change IC103 and then measure the waveform again. If IC103 is already
replaced, replace IC101 and then measure the waveform again.
Measure the waveform between pin 1 (LO) and pin 2 (COM) of IC104 with the oscilloscope.
Note: When measuring the waveform, short-circuited the PR102.
When the measured waveform is approximately 70 kHz, 15 Vp-p square wave, it is normal.
When the measured waveform is not normal, check the voltage between test point D136 cathode and E is approximately
+16 V. When measured voltage is +15 V or less, change IC104 and then measure the waveform again. If IC104 is already
replaced, replace IC101 and then measure the waveform again.
9
Turn the power switch off, install the fuse to the F101 and F102 and then turn the power switch on.
Check “2. Electrical Performance”.
When the result is good, the repair is completed.
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