Duplo DF-920 Maintenance Manual page 21

2-2-6. Adjusting the tension of the paper feed tray automatic up/down drive timing belt
(DF-920 only)
If the tension of the belt is not appropriate, problems
such as faulty drive and jumping of the belt will occur.
Move the tension idler and adjust the tension of the
belt so that it slacks by 3 to 5 mm (0.12" to 0.20")
when a pressure of 3 N (306 gf) is applied to the belt
using a 5 N (510 gf) tension gauge.
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