Riso GR 3750 alignment, drum and colour change questions

[ianmck]

1. Prints do not appear on the same place on the paper each time. This causes most problems when I switch drums to print a second colour over a previous print. Does anyone know how I can get the prints to appear consitently in the same place on the paper? Also is there a recommended time to wait for ink to dry before running a print through a second time?

2. I have the opportunity to pick up an extra colour drum, but it is not the colour I would like to use. Does anyone know a procedure for changing the colour of the drum?

3. I keep getting a "replace the ink cartridge" message one one of my drums when there is plenty of ink in the cartridge? Can anyone advise me of a solution?

Thanks to anyone who can help.