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Shaoxing Gangfeng Medical Products Co., Ltd

Time : 2021-12-10 Hits : 56

The electrocardiograph is one of the indispensable medical equipment in hospitals at all levels, and its paper-feeding failure is one of the common failures of the electrocardiograph. The paper-feeding speed-stabilizing circuit is composed of a paper-feeding transmission device or an AC motor, a control circuit and a paper-feeding mechanism. The stability of the paper speed directly affects the accuracy of the measured waveform time interval, and affects the doctor's diagnosis of the condition.

The causes and troubleshooting methods of paper feeding faults are summarized as follows:

1. No paper feed
First check whether the output voltage of the steady-speed circuit is normal. If it is abnormal, it means that the steady-speed circuit is faulty or the load capacity of the power supply is too low. Check whether the operating voltage of the steady-speed circuit is applied. Then check whether there are resistors and capacitors or transistor damage in the speed stabilization circuit. If the output voltage of the speed stabilization circuit is normal, check whether the lead wire from the output end of the speed stabilization circuit to the motor terminal is disconnected or disconnected. Finally, check whether the internal coil of the motor is open or short-circuited. If the above conditions are normal, the fault must be caused by the mechanical transmission part. Then check whether the connection between the motor shaft and the gear is loose, and whether the rubber shaft and the gear are jammed by dirt or foreign matter.

2. The speed control switch does not work and the paper speed is out of tolerance
It is generally caused by a steady-speed circuit, which is more common in models that use a stabilized source circuit as the paper voltage. Check whether the potentiometer in the paper feed stabilization circuit is disconnected or internally disconnected. If it is damaged, it should be replaced or soldered firmly, and then check whether the transistor in the circuit has broken legs, desoldering, breakdown, etc. Use a multimeter to measure the potential of each pin or measure the continuity of the PN junction.

3. The paper speed is unstable, fast and slow
Check whether the spring that compresses the driven shaft head is insufficient or damaged, then check whether there is slippage between the rubber shaft and the driven shaft, and further check whether the steady-speed circuit adjustment tube is aging. Simple self-test paper speed method: set the lead selector switch to "O" (1mV) position, feed the paper, and record the time by a stopwatch. At the moment of starting to record, record a 1mV standard distance wave, and then record after 7 seconds. For 1 pitch wave, count the number of small divisions x between the leading edges of the 2 pitch waves. If the distance between 1 small division is 1mm, the paper speed is: v=x/t(mm/s).

4. Periodic noise or noise during paper feeding
It is certain that there is a lack of lubrication or dirt between the gear and the gear, and the shaft and the shaft.

5. The recording paper is deflected to one side, curled or even torn during paper feeding
Is generally caused by mechanical failures such as uneven positioning of the hot pen holder or a large gap between the positioning holder and the guide shaft.

6. When tracing on the recording paper, tighten while loosening
Check the support spring, the spring support of the support spring should be evenly stressed, and then check whether the hot pen holder is uneven, just adjust it.