Intermec EasyCoder 501 – Service Manual Ed. 7
210
Chapter 26 Troubleshooting
26.3 Printing Troubles,
cont.
All or most dots printed
• If the printer unexpectedly produces completely or partially
black printout regardless of label layout, check the printhead
v24V. If too high, in the range of 40 to 50V, the trou-
ble probably originates from the power supply part of the CPU
board. Repair if possible, or else replace the CPU board.
The printhead probably damaged and needs to be replaced.
Printed line along dot row at startup
• Printhead probably damaged. See“All or most dots printed”
above.
Media feed does not work
• Clean the platen roller. Dust can deteriorate the media feed
function. Clean the label stop sensor as well while you are at it.
• Check the tension of the timing belt that drives the platen roller.
Adjust as explained in Chapter 8.4.
• Verify that a print command is actually issued in the current
Fingerprint program.
• If there is an interruption in media feed during printout, the
trouble may be that the program takes an unusually long time to
process data for each new dot row, which prolongs the interval
between motor steps. The stepper motor loses momentum and
may even stop completely emitting a whizzing sort of noise.
Remedy: Increase the image buffer as described in the Instal-
lation & Operation manual (Setup; Memory allocation). By
doing this, you preprocess more data before printing starts,
which speeds up the printout. Or else, avoid sending new print
data while the printer is busy with a printout.
• 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, sequen-
tially. The voltage will switch between 40V and 0V.
Also test the motor current by setting the second probe to each
pin 16 of IC-403 and IC-405. The curve traced by the oscillo-
scope should indicate a few tenths of a volt at intervals defi ned
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 kil-
ohertz. 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.