UBI EasyCoder 501 – Service Manual
197
26. TROUBLE SHOOTING, cont'd.
26.3
Printing Troubles, cont'd.
Paper feed does not work, cont'd.
• The stepper motor could be incorrectly connected (P-401), or its
drive circuits, IC-403 and IC-405 on the CPU board could be
damaged.
Check that all pins in the connector of the stepper motor's cable
are fully inserted.
Test that current is supplied through both motor windings by
means of an oscilloscope whose one probe is to be connected to
GND and the other probe to P-401: pins 1, 3, 5, and 7, sequentially.
The voltage will switch between 40V and 0V.
Test also the motor current by setting the second probe to each pin
16 of IC-403 and IC-405. The curve traced by the oscilloscope
should indicate a few tenths of a volt at intervals defined by the
stepping rate (magnitude: milliseconds).
If these measurements deviate from what is normal, check the
incoming signals ST 1-3 and ST 4-6 to IC-403 and IC-405,
respectively. They are all TTL level signals, and should vary
between low and high with a frequency in the range of kilohertz.
If they are found OK, the control and drive circuits IC-403 and IC-
405, or the CPU board, are probably damaged and the whole
board needs to be replaced.
Содержание EasyCoder 501 SA
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