Philips HD 7: No display in echo zone
Failure phenomenon
After the Philips HD7 color Doppler ultrasound is turned on, there is no image display in the echo area of the three probes, and no image is displayed when the gain is adjusted to the brightest.
Failure analysis
The machine can be turned on normally, indicating that the rear part is normal, but there is no image in the echo area generally because of the following two reasons:
(1) Part of the power supply module is faulty;
(2) The front-end circuit board is faulty.
Repair process
Open the casing of the machine, start the machine, and observe whether the indicator light of the power module is normal. After inspection, it is found that the indicator light is normal. Use a multimeter to measure the voltage of each group, which is consistent with the circuit requirements. The cause of the power supply can be temporarily eliminated.
Check the front-end circuit boards. After consulting the manufacturer’s engineers, we learned that this failure phenomenon is generally caused by the failure of the front-end circuit board DEMO or BPAP.
After careful inspection, it is found that there is a short circuit at both ends of the diode CR1608 on the front-end board DEMO. If the diode is disconnected from the circuit, the short circuit still exists, indicating that there are other components on the board short-circuit.
Use a multimeter to check one by one, and find that there are suspicious short circuits in the encoder U1500, voltage comparator U1604, rewritable memory U2001 and U2002. Pin 10 is short-circuited, replace the memory, install the front-end board, start the test run, the machine is in normal use, and the fault is eliminated.
