Every so often, we will get a service request for a scanner having feed issues: either frequent double-feeds, or difficulty feeding documents into the track at all. Quite often, the cause is a worn-out Self Adjusting Discriminator Roller (SADR) – the small foam disc that sits at the mouth of the feeder, opposite the drive rollers. Most people don’t even know what this component is, and fewer still realize that it is designed to be user-replaceable, without any tools, to save on downtime and expensive factory repairs.

What does the discriminator roller do?
With multi-feed scanners, it’s important to make sure that exactly one check at a time is pulled from the stack, and that’s the discriminator roller’s job. While the “drive rollers” that actually move the check have a rubber-polymer composition and almost never wear out, the discriminator has the much more delicate job of applying exactly enough pressure to grip a single check, and is therefore made of hardened foam. This material gives it the needed precision, but is also less durable, and the reason why it wears out after extended use.

When and how do I replace it?

Fortunately, “less durable” is a relative term: The lifetime of the discriminator roller is measured in the hundreds of thousands of scans before wear becomes a problem. (It is impossible to say exactly how long one will last, due to variables such as the coarseness of the paper scanned, heat and humidity, and others.) This means that many of our TellerScan series devices may only need to have the discriminator roller replaced once in their entire length of service, if at all. Of course, those in higher-use environments may go through several rollers before their mechanical end-of-life.

Unfortunately, the rarity of this repair means two things: 1) Most front-line operators will not know to look for it, and 2) It will almost always happen after years of service, well after the warranty has expired. This combination tends to lead to a lot of costly service calls that could be avoided with a little DIY initiative.

Diagram of TS240 with discriminator rollerReplacing the discriminator roller is easy: Simply remove the scanner’s top covers, pull the roller (colored blue for easy identification) straight up to remove it, and snap the new roller into place. To make it easier, you may use a ballpoint pen to hold the discriminator roller apart from the opposite roller while removing it, and again while replacing it. No other tools are required. The roller also has a convenient “D” shaped hole in the center to guarantee that it fits into place the correct way.

Replacement discriminator rollers for the TellerScan TS240 can be ordered directly from our online store for about $16 and swapped out in a few minutes – much better than hours of troubleshooting, and certainly an improvement over a $100+ factory repair and the downtime that comes along with it.

Did you know that our TellerScan TS240 scanners have color-coded parts to identify the ones that can be easily replaced? Most parts in light blue are designed for “snap-in, snap-out” replacement by the operator. Consult your user manual for additional information.