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Service required for HP 9160A Optical Card Reader
01-06-2016, 10:32 AM
Post: #18
RE: Service required for HP 9160A Optical Card Reader
Looking to the posted pictures, it seems fairly easy to do the diagnosis now.

- Test for power supply short circuits again, but without plugin in the two PCBs, then one OCB, tehn the other PCB, to find out where is the short-circuit.

- Also make sure that the burned inductor is not in open circuit.
If it is, temporally use a piece of wire to bypass it in order to allow the current to feed the electronics and the motor.

- Most probable what you see as a "0Kohm" reading would in fact be a lowish value, like 5 or 10 ohms, and that will be the normal internal resistance of the motor.

When the motor is energized, this lowish resistance value cause a large initial rush current, but this is normal and should not blow the fuse, as long as the motor can start rotating to let its impedance to rise fast to the normal value and let the current decrease rapidly.
(fuses can stand larger current than the specified value for a short time, specially if they are slow blow).

Now, if the motor can not rotating because it is mechanically blocked, its impedance will not rise and the current will remain high resulting in the issue that you describe (blown fuses and series resistors/inductors burnt).

Jose Mesquita
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RE: Service required for HP 9160A Optical Card Reader - jebem - 01-06-2016 10:32 AM



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