Maintenance techniques for SSD-118 ultrasound

With the development of computers and the large-scale integration of ultrasound circuits, controlled by several microprocessor control circuits, the instrument's storage, transmission, and processing of large amounts of information during operation become accurate, fast, and simplified. This greatly improves the reliability and stability of the instrument. On the other hand, due to the use of a large number of integrated circuits, once a circuit fault occurs, it is difficult to solve the problem simply by checking the voltage and current values with a multimeter.
Learning to use more advanced instruments like oscilloscopes to measure voltage signal waveforms based on the logical relationships indicated in the circuit diagram, and then using the changes in these signal waveforms as a basis to quickly determine the location of the fault can achieve good results with half the effort.
Of course, using an oscilloscope is not the only method. Logic analyzers, integrated circuit testers, etc., can also be effective testing tools. However, among the many testing tools, oscilloscopes have obvious advantages such as low price, simple measurement methods, ease of learning and use, and portability.
    When repairing ultrasound machines, various repair tools should be prepared. The following are recommended:
(1) Oscilloscope: Sensitivity 5mV/DIV, bandwidth DC 35MHz or higher, maximum input voltage 300V or higher.
(2) Multimeter: Grade DC 20000/V or higher.
(3) High-voltage test probe: Test range 30kV, used with a multimeter.
(4) External extension board: A dedicated extension board for each model, used to extend the board inside the machine to a position that is convenient for maintenance personnel to test.
(5) Screwdrivers: Including Phillips, flathead, short and thick handle types, and non-magnetic types.
(6) Soldering iron: 20w-25w internal heating type, with grounded shell.
(7) Wire cutters.
(8) Long-nose pliers.
(9) Solder.
(10) Leads with alligator clips.
(11) Integrated circuit test clip.
In addition, if conditions permit, dedicated testing tools can be equipped, such as dedicated test modules, BMI type, manufactured by RMI Company in the United States, specifically used for testing the human tissue simulation test block of B-type ultrasonic diagnostic instruments.

   With the repair tools, certain matters should also be noted during the repair process.
(1) To prevent damage to electrical components, the power should be turned off when unplugging or assembling cables and plug boards.
(2) High voltage on the display should be given high attention, and the high voltage should be discharged to ground before removing the cathode ray tube.
(3) When detecting and viewing waveforms, an extension board is needed.
(4) Check the instrument and cable for mechanical damage, the connection of each connector, whether the components are damaged, and the causes of faults caused by dust, water droplets, etc.
The SSD-118 mechanical sector scan ultrasound manufactured by ALOKA Company in Japan consists of a power supply unit, a transmitting and receiving unit, a physiological signal unit, a storage unit, a sector scanning unit, and a television monitor. I will analyze the typical faults that frequently occur in this model in daily work to improve the accuracy rate of future maintenance and fault diagnosis and the efficiency of troubleshooting.

Fault 1:There is no image on the entire screen.
Causes: (1) ±5V, ±15V, ±1.5V power supply abnormal; (2) Composite video signal interruption (EP-1831C); (3) Television monitor problem (IP-0504-TH); (4) Cable disconnection or bad connection.
Detection: (1) L-PS-25B, GN2±15VDC, GN2±1.5VAC; (2) EP-1827C, IC2D, PIN4.

 Fault 2:The screen image is chaotic.
Causes: (1) TV signal too low or too high; (2) Video signal out of sync; (3) Video monitor malfunction.
Detection: EP-1827, IC2D, PIN 4, IP-0504-TH, RV2.

Fault 3:Narrow horizontal stripes of black and white appear on the image.
Cause: This is mainly due to an integrated fault in the jump buffer memory or a problem with the peripheral circuits.
Detection: EP-1829, PIN11, PIN14, IC7A, 6A, 5C and 5D.

Fault 4:Vertical stripes appear on the screen, and graphic characters are not displayed.
Cause: There is a problem with the graphic memory or its peripheral circuits.
Detection: EP-1508C, IC5D, PIN4 and PIN5.

Fault 5:The ultrasound image is swinging horizontally.
Cause: Sector scan transducer failure, Address Generator failure, unstable motor speed.
Detection: EP-1831C TP1, EP-1831C TP2.

 Malfunction Six:The panel switch is malfunctioning.
 Cause: Panel interface malfunction (EP--1830C), back panel issue (EP-2042).
 Detection: EP-1830C, IC3C, PIN3, PIN9.
  After troubleshooting, a post-repair inspection should be performed using a dedicated test module (RMI412 type). The image displayed on the screen should be compared to the standard graphics provided on the module. Simultaneously, read the horizontal and vertical resolution values for near, mid, and far fields. If an I1MI module is unavailable, a B-ultrasound operator can perform a practical check and judge the post-repair quality from the resulting image. In short, a comprehensive check according to the standard or manual specifications must be completed before use.

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