thank you, MoHPC!! Being an enthousiastic HP Calculator user for over 20 years i am very happy to have found this website. With all the information i found here, i have been able to repair my card reader which has been ten years in a drawer! (-the cards would'nt get through anymore...).
I want to post this to the forum because apparently there is some confusion regarding the type of O-rings in the Article N°57 of Dave (an article in the Articles Forum). I found out that the type 006 O-rings are in fact the same as the englisch 1/4" OD - 1/8" ID. The 006 type has 2.9 mm ID and a rubber thickness of 1.78 mm, what makes an OD of 2.9+2*1.78=6.46 mm. Here you can find more info on O-rings: http://www.marcorubber.com/sizingchart.htm
In Tienen (Belgium) i could only find a metric O-ring size "01" of OD 6 mm and ID 3 mm which also works fine!
regards, Hugo