Ricoh MP C6502SP Field Service Manual page 1389

[A]: White spots
[B]: 40mm
[C]: Feed direction
Cause
Electrical discharge occurs at the PTR nip.
-In detail-
In low temp and low humidity environment, the resistivity of the PTR increases. To maintain the
prescribed electric current level in this adverse condition, the transfer voltage increases. Running
the machine in this condition using paper with high resistivity and low surface smoothness causes
electrical discharge at the PTR nip as a result of excessive transfer voltage.
The problem is likely to occur in the following conditions.
Model: D137/D138 only (AC transfer applies higher transfer voltage at the leading edge)
Environment : Low temperature & low humidity
Paper: High resistance & low surface smoothness
Image: Halftone
Solution
1. Decrease the paper transfer current from -75 micro A (default) to -60 micro A.
This will prevent the PTR voltage from increasing.
Possible side effect: Solid colors appear slightly faint.
2. Run a 50-100 page job. This will increase the machine internal temperature and prevent the
discharge from occurring at the PTR nip.
3. Request your customer to use paper with lower resistivity and higher surface smoothness.
Troubleshooting for White spots
Symptom
White or black spots appear when printing halftone images in low-temperature, low-humidity
environments (10C/15%) immediately after the developer is replaced.
• Black spots occur more frequently when printing onto coated paper.
Image Quality
1387