Intermec 074787-001 User Manual
Chapter 2 — Theory of Operation
PB42 Portable Receipt Printer Service Manual
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The printhead temperature sensor, SHTH, is not available by default. U40
must be installed to enable the ADC to read this voltage.
must be installed to enable the ADC to read this voltage.
Paper Feed and Backfeed
Asserting the FEED* and BFEED* signals (PE26 and PE27) causes the
print controller to feed the paper, respectively, forward and backward.
print controller to feed the paper, respectively, forward and backward.
Printhead Resistance Test
Every time the print controller starts up, it conducts a printhead resistance
test to verify that each dot is within tolerance for its resistance. The voltage
that the print controller measures is also connected to channel 7 of the
ADC (signal name is SHR). Using channel 7 enables the microprocessor to
monitor this test and determine which dot is out of tolerance.
test to verify that each dot is within tolerance for its resistance. The voltage
that the print controller measures is also connected to channel 7 of the
ADC (signal name is SHR). Using channel 7 enables the microprocessor to
monitor this test and determine which dot is out of tolerance.
SHR Signal After Startup of the Print Controller
The printhead being tested in this example has a large section of failed dots.
The print controller runs the test twice every time it starts up. The next
illustration shows the same signal, but zoomed in significantly to see the
voltage levels of each individual dot.
The print controller runs the test twice every time it starts up. The next
illustration shows the same signal, but zoomed in significantly to see the
voltage levels of each individual dot.