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VQiservice manual download site
When the battery is good, should use the multimeter to test the main circuit board p 2 feet voltage socket, and repeatedly open and shut down, if the fundamental voltage, the fault in the system control circuit; If you have around 1 v drop point voltage in the boot, fault in the power circuit itself. Power circuit of the common point of failure is: the battery reed poor contact; Poor contact inside the adapter socket; Connectors P1604, P1501, P1602 virtual welding; Inductor L1601, diode D1603 virtual welding, etc., can examine these components. VQiservice manual download site
VQiservice manual download site
Maintenance example VQiservice manual download site
VQiservice manual download site
[example 1] failure phenomenon Electrical switches can't boot, light is not bright. Analysis and repair The first to test the power supply circuit. Measurement with multimeter dc voltage 50 v socket voltage of 12 v normal P10012 foot, IC1001 attending, continue to test 3505. GIF (116 bytes) feet also have 12 v working voltage. At this point, the edge electrical switches to boot, the edge detection of the power on and off pipe Q1006 each voltage, found Q1006 base voltage does not vary with the power switch on a low level, same as the Q1006 emitter voltage and voltage, are about 12.5 V, and in the normal boot state, Q1006 emitter voltage is about 12.5 V, the base voltage is about 11.7 V, the collector voltage is about 12.5 V, so doubt Q1006 damage. Welding under Q1006 sb970x (2) inspection, found that the breakdown, b, e electrode b and c electrode has open circuit damage. After new tube with the same substitution, machine work back to normal. VQiservice manual download site
[example 2] failure phenomenon with case 1. VQiservice manual download site
Analysis and repair First of all stripes in the power circuit voltage testing, found the + 5 V output voltage is only 2.5 V. Check this load, there is no short circuit, so the question the fault + 5 v voltage control loop. VQiservice manual download site
When check the + 5 v voltage control circuit, first check the voltage sampling circuit. Voltage sampling circuit by resistance R1001 Ω (6.8 k), R1002 Ω (2 k) and fine-tuning resistance VR10001 Ω (500), such as 5 v voltage by R1001, R1002, VR1001 after partial pressure from VR1001 center moving piece sample output voltage feedback to IC1001 {30} feet, to maintain the stability of 5 v voltage. VR1001 R1001 measurement on the terminal voltage of 2.5 V, test center piece also voltage of 2.5 V, and according to the principle of partial pressure, about half of the voltage of the voltage shall be the R1001. Now two equal potential, is likely to be VR1001 open circuit between the bottom to the ground, destroyed the resistor in series with the partial pressure channel, make the above two points equal potential. Damage of actual measurement, indeed for VR1001 lower open circuit. Replace a new trimming resistor, troubleshooting.
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