IBM 3112, Service Manual

Page: 30 / 184

bh1s.bk : bh1sdiag.doc 14 Thu Apr 20 12:42:16 1995
14
Service Manual
Banding
Banding appears as light and dark horizontal lines on a page that is
supposed to be uniformly gray. It is due to variation in the speed of the
paper as it moves from roll to roll during development or transfer. It is
undetectable when printing text and is most noticeable on fine dot or
horizontal line patterns such as the second page of Print Test 2 or Print
Test 3. Inspect the gear train and the paper feed rollers for wear, dam-
age, dirt, or binds.
Background
Areas that are supposed to stay blank are getting small amounts of
toner deposited on them. Clean the erase lamps and the printhead win-
dow.
Verify that all the erase lamps are working by powering on or off with the
top cover open. Verify that there is +24VDC on engine board J9-1 and
b15 and +20VDC on engine board J9-2. Shorting engine
board J9-2 to ground should turn on all the erase lamps. Check the
erase lamp cable continuity. Replace the transfer roll housing if the volt-
age and the cable are good.
Inspect the contacts on the HVPS; make sure each spring-loaded con-
tact returns when pressed and released.
Rough Paper mode can cause background on some papers; if Rough
Paper mode is on, turn it off and run the print test again.
Printing on coated paper or using refilled print cartridges can also cause
background.
Run the Print Test with the RIP Board removed and check the following
Horizontal Void or Streak Horizontal Service Check
Vertical Void or Streak Vertical Service Check
Banding Banding Service Check
Symptom Action or Service Check