Hitachi EUB-5500 Ultrasonic Troubleshooting(3)
Fault phenomenon
After the circuit breaker is closed, press the power on key, the machine does not respond, all indicator lights on the operation panel and display are not on, and the fan does not rotate.
Troubleshooting
Measuring power box fuse are normal, measuring input voltage 220V are normal.The 220V voltage is lowered to 110V through the transformer inside the power box and input to the power board. The 110V voltage is measured normally.Two circuit boards were removed from the power box. After careful inspection, it was found that the PNP transistor D1858 on the circuit board was broken. At the same time, it was found that some other components around the transistor were damaged.
Hitachi eub-5500 color ultrasound normal boot is divided into two steps.The first step is that the breaker switch is closed and 110V voltage is conducted into the circuit board. At this time, the start circuit in the power box has started to work and is in standby state, waiting for the start signal.The second step is to press the start button, switch and conduction, and send a low-level start signal to inform the power box to start working.The circuit of D1858 is a standby circuit.The standby circuit fault causes the power box to be unable to receive the normal start signal, making the power box unable to start normally.After replacing the D1858 transistor and surrounding components, the machine recovers.
This fault is common on Hitachi eub-5500 color ultrasound for two reasons:
(1) The operation of the use of habits.After the machine is used every day, the machine is not shut down according to the normal shutdown process, and the circuit breaker switch is not closed after the system is shut down, so that the standby circuit in the power box is always in a live standby state, seriously affecting the life of this part of the circuit.
(2) The machine power box did not timely dust, filter screen blockage, power box can not normally heat, resulting in overheating and burnt circuit board.
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