DUS 60 Digital Ultrasonic Diagnostic Imaging System Service Manual
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principles, so, it is very important to prepare and conserve device information (Circuit drawing,
Service manual, etc.).
6.5.4. Eliminating malfunction
The method of eliminating malfunction should be selected according to the malfunction. The
usual way is changing the defective and damaged components. Some malfunctions are caused
because of the maladjustment of some components, well then, the components should be checked
and debugged via instrument or meter to eliminate malfunction. The circuit B-mode ultrasound
has been highly integrated, and it is a high specification requirements for the welding of the chip,
so some specific purpose tools are used, such as solder sucker and extractor for IC chips. Weld
the IC carefully, otherwise, the circuit board will be damaged.
6.6. Basic Method of Checking Malfunction
The most important key of checking malfunction is isolating malfunction, to check malfunction is
to isolate malfunction and find out the malfunction components and parts.
6.6.1. Confirming the Malfunction Part
You can use the knob and button on panel to confirm the malfunction part. After finding out the
malfunction phenomena, the malfunction parts could be estimated according to the operating
principles of circuit. However, the veracity of estimation should be proved by many means, such
as measuring the circuit voltage and wave shape. For some malfunction, you can use the knob
and control button to define the malfunction scope directly. It is easier than measuring inside the
device. When checking the malfunction of low sensitivity of the knob or buttons, it is available to
watch whether the enlarging circuit is running normally through adjusting the gain knob or not.
Under the normal condition, it always produces certain noise to display on the screen to receive
the circuit, When adjust the gain control knob, there are obvious power changes in the noise, this
can generally prove that the receiving circuit is running normally. The reason for low sensitivity
may probably be caused by the transmission circuit or probe. There are also some adjusting knobs,
they can't make the trouble disappear after adjusting, but can lead to the change of the
malfunction phenomenon. This can contribute to the judgment for the malfunction too.
6.6.2. General Checking After Opening the Cover of the Unit
If the malfunction is happened inside the unit, it needs to open the cover of the unit for a further
checking. After opening the machine cover, every components and parts are exposed to us. The
first step is to check all the components and parts by the eyes, ears, and nose, but not by hands,
because some components, especially the transistor, IC have many terminals, which are very
fragile and can be damaged easily. Check whether the component of resistance is burned or
changed color, whether the capacitance is broken, whether the pin of the transistor is rusted and
broken, whether there is dirt on the pin of the IC, whether the plug-in chip is falloff and whether
there is short circuit and weak welding for the pins of the components, etc. Then electrify the
device to observe carefully whether the indicator light is on, whether there is jumping fire,
flashing fire or smoking between the components of the circuit board. Listen whether there is
“pa-pa” sound inside the components and whether there is “weng-weng” sound from transformer;
smell whether there is burn
paint flavor from the transformer, resistance, ozone flavor that the
high pressure discharges, etc. Switch off the device immediately if meet something abnormal and
touch the doubtful components such as transistor, integrated circuit, transformer to feel whether it
is too hot. At this moment, you must be careful not to move the terminal of the components to
avoid damage. For the safety of the high voltage part, should firstly discharge the high voltage
capacitance. If there is no abnormal phenomenon after switching on the device, you can try some
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