MS-Access databases can store binary data in columns of type "OLE Object". But the Access Input step turns this data into strings which look like "[B@1f8320".
Looking at the code for the org.pentaho.di.trans.steps.accessinput.AccessInput class, it seems that conversion of the values returned by the Jackcess library is performed by converting to a string, then to a PDI type. But binary data is returned as byte, and when converted to a string the contents is lost. However, dates are already treated specially (they are used directly without conversion), and the solution to this bug is to treat byte references in a similar way.
A patch is attached.