Where is the drum located in a Canon 940 copy machine

If line appear on drum scratched change drum & cleaning blade.otherwise change only cleaning blade

clean the machine and replace the drum cleaning blade

Could be optics needing to be cleaned. First I would rule out the toner cartridge. If you have a spare swap it out or remove your current cartridge, turn it over and slide open the "gate" that covers the drum cyclinder. The drum should be clean all the way across it's surface. If you see toner on each end then that is where your dark sides are coming from. If the drum is clean then most likely you have dust building up on the optics mirrors. One test for this is to manually lighten the exposure control on the operation panel and then recheck your copy quality. This may cause the rest of the copy to be light but if the dark sides goes away then your optics are dirty.
Good Luck and Thank You for using Fixya.

Vacume the interior of copier, check the drum.If there is spots on drum, change the drum.
Also check the fixing section.

Hello sir; Discharge corona unit dirty it cause this problem, got to be discharge corona wire covered by tone, clean outby rubbing alcohol,it will take care your problem.

Have you replaced the drum cartridge yet? Or did you and this what you are getting. If the old drum was working ok, but dark. You may have a defective drum unit.

The transfer roller seats under the drum unit. You most likely need a new drum unit. Have you pulled the drum out and dose it have black lines on it? If so, that is where the problem is.... Or it could be coming from the fixing unit..

The waste toner is in the drum unit it's self. If it full you may as well replace the drum unit all togather. Once it is full the drum is just about shoot. If the regestration is off, you may have a problem withe reg. feed clutch. Dose it show up with the paper tray and the manual feed try?

There are no fiber optics in the copier. It has 6 mirrors that send the image to the drum unit. Did you try to clean the copyboard glass? Also, do the marks move up and down the page? Also, have you replaced the drum cartridge recently? Pull the drum unit out can you see track marks on the drum it self. If not I would have to say it may be comming from the fixing ass'y, the hot part of the copier. Try to use a dry rag and wipe up any loose toner in the paper path then try to run some blank pages in the copier this may clear up the problem...

You could have a broken exposure lamp. Does the scan bar light up when you make a copy? If not that is the problem. You might also ck the contacts on the machine where they touch the toner cartridge. The toner cartridge opens a shutter to the drum when you slid it into the machine and that may be broken.