office printer occasionally prints lines down paper from bypass tray only

[teragramrk]

I print large batches of letters several times a week.  Because I use several different letterheads, I exclusively print from the bypass tray.  Often, the printer will print a reddish or faded black line down the left margin of the top or top several letters of each batch.  It doesn't always, and sometimes there's a hint of the line somewhere on each page regardless of how large the batch is (upwards of 100 pages sometimes).  When this happens, I have to reprint certain letters until they finally come out clean, but there is no way of knowing how often or when that will be, thus wasting a lot of paper and ink.  These lines don't occur when printing from the regular printer trays, nor do they occur on envelopes printed from the bypass tray.

It seems as if there is an issue with one of the outside rollers for the bypass tray, but I don't know how to determine which one or how to fix it.  Any ideas?

[Repairatrooper]

Can you post some samples. The most common problem we find with this particular design of printer is the transfer belt leaving traces due to the waste toner hopper not draining toner into the waste bottle. 

[teragramrk]

I can't post the letters because of privacy concerns, but I'm trying to recreate the problem on regular paper.

[teragramrk]

Here is an example of what I'm talking about.  It took me almost 10 prints of this letter to get a clean copy with no trace of this line.  The line isn't always this pronounced, but it's a pretty common occurrence that is quite the inconvenience. 

[Repairatrooper]

Most common cause is waste toner buildup in the waste toner collector (green circled item in photo one below) on the end of the transfer belt. It is supposed to drain into the waste toner bottle but that does not always happen. You can try removing the transfer belt, and holding the shutter on the left front open (red circle photo one and photo 2)  over a garbage can with the left side lower than the right and tap the waste bin to get the toner to run out. Occasionally a polluted secondary transfer roller can cause this error but this is less likely.

Photo One 500 series transfer beltPhoto Two 500 series waste toner shutter