Need help with trouble shooting SP 540i

[Designersigns]

We have banding issues that we can't resolve on our SP 540i. It is a wide light color band that presents itself differently. Sometimes it will show up every few inches, other times it will be every few feet. It seems to bemost prominate in cyan and black but it does run through all colors faintly. It also prints somewhat grainy. We replaced the dampers and the caps first.We had the tech out and he could not find the problem. He ran it through the usual paces, tried a new print head, swapped it back after it didn't fix it then referred to the Roland field tech who suggested the feed motor as the cause. We cleaned the gear at the motor which was pretty dirty, calibrated it and it worked beautifully for a couple of weeks then it started again. We contacted Roland tech support, sent print tests and they suggested either a feed motor problem or thermistor. We replaced both and it made no difference. Now what? What else can I check? Does anyone have a service manual for this?

 

[woolly]

As you say it goes grainy as well as feint manly black cyan same head my guess would be static but surprised that it did not disappear after changing the head.
As a quick cheap test wipe the whole machine with a slightly damp cloth care not to catch on any thing inc the bed and head area and change material for any other type. Test print

 

[Designersigns]

We have explored static and as a matter of course we have a static control tinsel hanging on the back.