Instruction manual

3–33Troubleshooting
Print Quality Problems
Garbled print or paper slews
uncontrollably.
1. a) Put the printer in hex dump mode and analyze the
binary data. One cause of garble is the host interface or
cable not transmitting all 8 data bits. When this occurs,
the Centronics interface receives a 1 on every
unconnected data line. Uncontrolled slewing is often
caused by enabling PI (Paper Instruction) in the printer
when the host lacks a PI signal. (PI shows as “p” on the
hex dump printout.) Some RS–232 interfaces only send
7 data bits. In this case, the eighth bit will be received as
a one.
b) In RS–232, a common cause of garble is the interface
set to the wrong baud rate or parity. Sometimes the host
sends 1.5 or 2 stop bits; in this case, the printer’s
“1–stop–bit” setting will accept both 1.5 and 2 stop bit
data. Sometimes the data may “fade” or “persist” from
one character to the next. This reveals a problem with
Centronics terminating resistors on the controller
board—especially if they are absent. Garble also can
result from failed terminating resistors or parallel logic,
but this is rare.
2. Replace the controller board.
Missing print over a single hammer’s
zone.
1. Replace one at a time until problem is fixed:
a) shuttle frame assembly (page 5–42)
b) controller board (page 5–10)
Missing print over every 4th hammer’s
zone.
1. Replace one at a time until problem is fixed:
a) controller board (page 5–10)
b) shuttle frame assembly (page 5–42)
No hammers fire but paper advances.
1. Replace one at a time until problem is fixed:
a) controller board (page 5–10)
b) shuttle frame assembly (page 5–42)