Appendix C: Service and Maintenance92
Minimize the exposure of your calculator to dusty, dirty environments by storing it in the soft carrying case when not in use. Each card pack contains one head cleaning card.
The magnetic recording head is similar to magnetic recording equipment. As such, any collection of dirt or other foreign matter on the head can prevent contact between the head and card, with consequent failure to read or write. The head cleaning card consists of an abrasive underlayer designed to remove such foreign matter. However, use of the card without the presence of a foreign substance will remove a minute amount of the head itself. Thus, extensive use of the cleaning card can reduce the life of the card reader in your HP-65. If you suspect that the head is dirty, or if you have trouble reading or writing programs, by all means use the cleaning card; that’s what it is for. However, if one to five passes of the cleaning card does not clear up the situation, send your calculator in for service.

Annotating a Card

You can write on the non-magnetic side of your card using any writing implement that does not emboss the card. It is customary to write a program name on the top and to write symbols identifying the functions of the top row keys in the spaces below. Annotating magnetic cards with a typewriter may impair the read/write properties of the cards.

Using Alternate Track

It is possible to store a program on the opposite edge of a card (and to later read it) by inserting the other end (opposite to the arrowhead), face up. Thus, a card can hold two 100-step programs. However, we recommended that you use only one track since:
1. Second program cannot easily be labelled.
2. Extreme care must be taken in protecting the second program. (Do not clip more than you would on the first track or you may lose information.)