Javascript get .pdf

Če gledam v firefoxu, v primeru da dela, XHR response:

%PDF-1.3 ....
...... en kup non readable podatkov
%%EOF

link
Tole ne dela nič, pride na servlet po podatke, na klientu pa je response = null.
xhr.onload,xhr.onerror se ne sproĹžita

 function loadPdfBlob(u_id)
        {
          var xhr = new XMLHttpRequest();
xhr.open('GET', contextPath + 'servlet path?u_id='+u_id, true);

xhr.responseType = 'arraybuffer';

xhr.onload = function(e) 
{
  if (this.status == 200) 
  {
    var uInt8Array = new Uint8Array(this.response);
    var i = uInt8Array.length;
    var binaryString = new Array(i);
    while (i--)
    {
      binaryString[i] = String.fromCharCode(uInt8Array[i]);
    }
    var data = binaryString.join('');

    var base64 = window.btoa(data);

    document.getElementById("pdfFrame").src="data:application/pdf;base64,"+base64;
  }
};

xhr.onerror = function(e) {
  alert("Error " + e.target.status + " occurred while receiving the document.");
};

xhr.send();  
          
        }  

Tole dela, ampak ne pikaĹže pdf-ja (XHR respons , kot zgoraj, na vrhu)

<input type ="button" value ="A" onClick ="$.get('servlet path',{ u_id:'<%=con.rs.getString("u_id")%>'},function(data){ document.getElementById('pdfFrame').src = data;})"/>

Kaj je za popravit ? Blob iz baze je zgleda OK.