Hi,I found a Panasonic bulletin.Hope this helps.Symptom:Copy image density becomes lighter although TDC is working correctly.Cause:TDC compensation control by Left off timer is working with negative effect and it results TDC level became lower.Field action :￼￼￼￼￼￼￼1. 2. 3.Please change the parameter setting F5-61 : TDC Auto Adjustment (DEV Conditions) from 1:Yes to 0:No.After changing F5-61 setting, please make about 50 copies using Test chart 53/54.If the image density does not become darker enough even after above changes, please put three (+3) steps in F6-62 (TDC Gain Voltage Adjust).Note : If there is high copy/print volume customer (ex. 5,000 copies/day), we recommend to leave this setting as “Yes” .Factory action :We are now studying new method for TDC Auto Adjustment and will implement it to the new firmware. It will be announced by Technical information when new firmware becomes available.